[Drakelist] R-4B Panel Wanted
Still looking for a NOS R-4B panel I have a new set of R-4B audio mods coming that go one step further than the Sherwood AMP-4 mod I recently made. I had FAR Circuits make several 4-watt audio amp boards using a modified SM0VPO design. Ultra low-noise discrete transistor design in the gain stage and a pair of TIP41 high-current drivers. Uses a string of 1N914 diodes in a Darlington circuit to minimize crossover distortion. I've been looking a very long time for an audiophile-grade amp that runs from a single supply, delivers low distortion, low noise, and will work equally well when driving a low-Z speaker or headphones. Nearly all current designs require a +/- bi-polar supply to achieve that objective. Links to photos coming soon. Paul, W9AC ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] FS - 160 thru 2 meter C-Line Station
Drake C-Line Station For Sale 1-R-4C, S/N 19160 w/ accessory crystals for 160m, 30m, 17m, and 10m cw. It has the Sherwood SSB filters, the Sherwood PS board and the Sherwood audio amp installed. It also has the Drake 1.5, 500 hz, and 250 hz filters. 1-T-4XC, S/N 29828. This unit has the Drake modification done for the 6 2 meter transmitting converters. 1-AC-4/MS-4 combo, S/N 59177. This power supply has the AC4R update installed. 1-TC-6 Transmitting converter for 6 meters, S/N 04X. The AC-4 power jumper cable is included. 1-TC-2 Transmitting Converter for 2 meters, S/N 0275. The AC-4 power jumper cable is included. 1-CC-1 Receiving converter Console, S/N 391. It has the CPS-1 power supply, the SCC-1 Calibrator, a SC-6 6 mtr. receiving converter and a SC-2 2 mtr receiving converter installed. 1-D 104 microphone with a Heil cartridge and a Drake connector installed. This equipment comes with all manuals, schematics, and interconnecting cables. This equipment is in good shape and it is all working but because of it’s age is being sold as is. I will package and ship the equipment but the buyer will have to cover the shipping costs. I would prefer a local pickup in the Dayton, OH area. PRICE- Complete station as listed-- $1495.00 plus shipping Inquires can be made to _w8njr@aol.com_ (mailto:w8...@aol.com) ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] My R-4B audio?
I have a R-4B here that I'm thinking is still low on audio output?? For those that have one toowhere is the 'normal' setting of the AF gain for you For a pretty loud level, not super loud just a nice loud level you could here fine on loud signals of S9 or so . What setting on yours would you consider super loud and want to turn it down? Seems like I have to use around 1:00 on the AF gain to get decent loudness. I'm just trying to find out if my audio is pretty normal?? Thanks, 73, Lee ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Lee - I rarely turn mine above 11 o'clock. What speaker are you using?? The amplifier is designed for a 4 ohm speaker. An 8 ohm speaker (MUCH more common these days) will reduce the overall output. Try bridging C176. A high ESR (dried out) cap here will reduce the gain of the stage considerably. Also verify approximately 4.5 VDC on the Cathode (Pin 1) of V7. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com kc9...@aol.com wrote: I have a R-4B here that I'm thinking is still low on audio output?? For those that have one toowhere is the 'normal' setting of the AF gain for you For a pretty loud level, not super loud just a nice loud level you could here fine on loud signals of S9 or so . What setting on yours would you consider super loud and want to turn it down? Seems like I have to use around 1:00 on the AF gain to get decent loudness. I'm just trying to find out if my audio is pretty normal?? Thanks, 73, Lee ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Digest Posts
Thom, Being a lurker and not much of a poster, I can't tell you how pleased I was to see your post regarding quoting. I really believe that some list members just do it without thinking - It's just SOP for them and they don't think (or bother) to change their email settings when posting. But, having to sort through all of the chaff to find the wheat in the digest version can be challenging when multiple posts are quoted time after time. So, I second the cool the quotes thinking and would like to suggest that it be expanded to all replies and not just those that pertain to the digest version. Note that I am not suggesting that quoting be eliminated - Only that it be moderated by using good judgment when replying. And, yes, I also subscribe to the reply first / quote last method because it makes it so much easier to find the wheat. This is especially true when multiple messages are quoted (see above!) and the new post (reply) appears many lines below. Plus, if you are already following thread, you probably don't need the quoted messages anyway. Regards, Bill In a message dated 3/30/2011 11:00:47 AM Central Daylight Time, drakelist-requ...@zerobeat.net writes: Message: 7 Date: Wed, 30 Mar 2011 07:59:23 -0400 From: Thom LaCosta k3...@zerobeat.net To: drakelist@zerobeat.net Subject: [Drakelist] Digest Posts Message-ID: mailman.2.1301500802.32728.drakel...@zerobeat.net Content-Type: text/plain; charset=us-ascii; format=flowed If you reply to a digest post...PLEASE change the subject to reflect the specific subject, NOT Drakelist Digest, Vol xx, Issue xx I would also appreciate you not quoting the entire digest post...it simply uses too much bandwidth. Thanks 73, Thom k3hrn ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
- Original Message - From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Friday, April 01, 2011 7:13 AM Subject: Re: [Drakelist] My R-4B audio? Lee - I rarely turn mine above 11 o'clock. What speaker are you using?? The amplifier is designed for a 4 ohm speaker. An 8 ohm speaker (MUCH more common these days) will reduce the overall output. Try bridging C176. A high ESR (dried out) cap here will reduce the gain of the stage considerably. Also verify approximately 4.5 VDC on the Cathode (Pin 1) of V7. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com I don't agree with this. The level produced by a speaker has more to do with its design, size of magnet, etc, than its nominal impedance. I have both 4 and 8 ohm speakers here, the loudest is an 8 ohm speaker probably for a Hammarlund receiver. I have a couple of 4 ohm speakers which are not so loud on the R4 or on a Collins R-388 which also has a nominal 4 ohm ouput. Curiously enough Collins speakers are 8 ohms. With the Hammarlund speaker the volume control is around 10 or 11 O'clock, for some other speakers it must be around 2 O'clock. If yours needs to be higher it may indicate either a bad speaker or some audio problem. I would also check with known good headphones. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
- Original Message - From: kc9...@aol.com To: drakelist@zerobeat.net Sent: Friday, April 01, 2011 6:45 AM Subject: [Drakelist] My R-4B audio? I have a R-4B here that I'm thinking is still low on audio output?? For those that have one toowhere is the 'normal' setting of the AF gain for you For a pretty loud level, not super loud just a nice loud level you could here fine on loud signals of S9 or so . What setting on yours would you consider super loud and want to turn it down? Seems like I have to use around 1:00 on the AF gain to get decent loudness. I'm just trying to find out if my audio is pretty normal?? Thanks, 73, Lee Another afterthought. The speaker jack in the back is connected through a contact on the headphone jack on the side of the RX. If the switch gets flakey it can cause the audio level to drop. Work the jack with a plug a few times to see if it helps. Also, the jack is connected right across the output transformer so you can plug a speaker into it. If its louder that way its an indication that the jack switch or perhaps wiring or the RCA jack on the back has a problem. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Richard Knoppow wrote: - Original Message - From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Friday, April 01, 2011 7:13 AM Subject: Re: [Drakelist] My R-4B audio? Lee - I rarely turn mine above 11 o'clock. What speaker are you using?? The amplifier is designed for a 4 ohm speaker. An 8 ohm speaker (MUCH more common these days) will reduce the overall output. Try bridging C176. A high ESR (dried out) cap here will reduce the gain of the stage considerably. Also verify approximately 4.5 VDC on the Cathode (Pin 1) of V7. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com I don't agree with this. The level produced by a speaker has more to do with its design, size of magnet, etc, than its nominal impedance. I have both 4 and 8 ohm speakers here, the loudest is an 8 ohm speaker probably for a Hammarlund receiver. I have a couple of 4 ohm speakers which are not so loud on the R4 or on a Collins R-388 which also has a nominal 4 ohm ouput. Curiously enough Collins speakers are 8 ohms. With the Hammarlund speaker the volume control is around 10 or 11 O'clock, for some other speakers it must be around 2 O'clock. If yours needs to be higher it may indicate either a bad speaker or some audio problem. I would also check with known good headphones. Richard - I don't agree with THIS!! :-) Granted, there are considerable variations in speaker efficiency related to all the factors you mentioned and more. BUT, if you have an amplifier with an output matched to a 4 ohm load, and hang an 8 ohm speaker on it, the speaker efficiency will be less due to mismatch, _all else being equivalent_!! This is even more important with solid state amps because of the current operated nature of these. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Now THIS I agree with! :-) 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com Richard Knoppow wrote: - Original Message - From: kc9...@aol.com To: drakelist@zerobeat.net Sent: Friday, April 01, 2011 6:45 AM Subject: [Drakelist] My R-4B audio? I have a R-4B here that I'm thinking is still low on audio output?? For those that have one toowhere is the 'normal' setting of the AF gain for you For a pretty loud level, not super loud just a nice loud level you could here fine on loud signals of S9 or so . What setting on yours would you consider super loud and want to turn it down? Seems like I have to use around 1:00 on the AF gain to get decent loudness. I'm just trying to find out if my audio is pretty normal?? Thanks, 73, Lee Another afterthought. The speaker jack in the back is connected through a contact on the headphone jack on the side of the RX. If the switch gets flakey it can cause the audio level to drop. Work the jack with a plug a few times to see if it helps. Also, the jack is connected right across the output transformer so you can plug a speaker into it. If its louder that way its an indication that the jack switch or perhaps wiring or the RCA jack on the back has a problem. ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: drakelist Drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 4:54 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Friday, April 01, 2011 7:13 AM Subject: Re: [Drakelist] My R-4B audio? Lee - I rarely turn mine above 11 o'clock. What speaker are you using?? The amplifier is designed for a 4 ohm speaker. An 8 ohm speaker (MUCH more common these days) will reduce the overall output. Try bridging C176. A high ESR (dried out) cap here will reduce the gain of the stage considerably. Also verify approximately 4.5 VDC on the Cathode (Pin 1) of V7. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com I don't agree with this. The level produced by a speaker has more to do with its design, size of magnet, etc, than its nominal impedance. I have both 4 and 8 ohm speakers here, the loudest is an 8 ohm speaker probably for a Hammarlund receiver. I have a couple of 4 ohm speakers which are not so loud on the R4 or on a Collins R-388 which also has a nominal 4 ohm ouput. Curiously enough Collins speakers are 8 ohms. With the Hammarlund speaker the volume control is around 10 or 11 O'clock, for some other speakers it must be around 2 O'clock. If yours needs to be higher it may indicate either a bad speaker or some audio problem. I would also check with known good headphones. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Richard, Good sugestion...I'll check it out now. Also, just a second thought on the speaker impedance...based on my experience in Audio as well as Ham...one should match the impedance of the speaker to the impedance designed into the audio output circuit, mostly. 73, Lee -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: drakelist drakelist@zerobeat.net; kc9cdt kc9...@aol.com Sent: Fri, Apr 1, 2011 5:02 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: kc9...@aol.com To: drakelist@zerobeat.net Sent: Friday, April 01, 2011 6:45 AM Subject: [Drakelist] My R-4B audio? I have a R-4B here that I'm thinking is still low on audio output?? For those that have one toowhere is the 'normal' setting of the AF gain for you For a pretty loud level, not super loud just a nice loud level you could here fine on loud signals of S9 or so . What setting on yours would you consider super loud and want to turn it down? Seems like I have to use around 1:00 on the AF gain to get decent loudness. I'm just trying to find out if my audio is pretty normal?? Thanks, 73, Lee Another afterthought. The speaker jack in the back is connected through a contact on the headphone jack on the side of the RX. If the switch gets flakey it can cause the audio level to drop. Work the jack with a plug a few times to see if it helps. Also, the jack is connected right across the output transformer so you can plug a speaker into it. If its louder that way its an indication that the jack switch or perhaps wiring or the RCA jack on the back has a problem. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
In a message dated 4/1/2011 7:31:45 P.M. Eastern Daylight Time, kc9...@aol.com writes: Also, just a second thought on the speaker impedance...based on my experience in Audio as well as Ham...one should match the impedance of the speaker to the impedance designed into the audio output circuit While this is generally true, be careful. Some years ago an attempt was made to match a set of low-Z headphones to the 600 OHM HEADPHONES ONLY jack on a commercial audio mixing console using a 600-ohm to 4-ohm audio transformer. Unfortunately, while the transformer may have had an AC *IMPEDANCE* of 600 ohms, the *DC RESISTANCE* of the winding was too low and, over time, it burned out the directly-coupled output transistor in the console by forcing it to source too much current to the load. MORAL: Pay attention to the configuration of the driving circuit before you arbitrarily hang something on the output. 73/Paul, K4MSG ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
- Original Message - From: kc9...@aol.com To: 1oldle...@ix.netcom.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:26 PM Subject: Re: [Drakelist] My R-4B audio? Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee The Collins catalogue, to be found on the Collins Collector's site lists the speaker as being 8 ohms. I don't have one so can't measure it. The speakers I have were measured on a General Radio 1603-A Z-Y bridge at both 1 khz and 400 hz. 400 hz is the standard frequency for measurement. There are several things of importance here; first, the impedance of a direct radiator loudspeaker is not constant. It tens to rise at a resonance at the lowe and and also tends to rise at higher frequencies, the two beign for different reasons. The low end rise can be to many times the 400 hz value and will depend on the efficiency of the motor and degree of coupling of the cone. In any case, its typically well below the frequencies of interest for voice communication. The mid-range efficiency also depends on the motor and cone coupling but usually at mid speech frequencies the cone sees a pretty good acoustical impedance match to the overall efficiency in terms of loudness is due mostly to the motor. The more powerful the magnetic field in the gap the louder the speaker will be. This variation can be quite large when comparing cheap, starved magnet speakers with high quality speakers with good magnets. By large I mean ten db. The amplifier in a Drake 4B is a very simple single-ended Class-A pentode stage with no feedback. Such amplifiers tend to have very poor voltage regulation (low damping factor), they are essentially constant current sources. That means the output will actually rise with rising impedance. One result of this is the accentuation of bass resonance in simple enclosures and the tendency to make some loudspeakers sound strident because of their rise in impedance at high frequencies. The mismatch can also increase distortion if excessive. While the total power available may be lower with a mismatch the voltage across the speaker may become higher. The practical effect is that the distortion may become greater at some level. Nonetheless the difference between 4 and 8 ohms should not make a great difference and an 8 ohm speaker may actually be louder. Now, the difference between 4 ohms and 600 ohms is 150 times, that is a lot so one would expect the difference in level to be very great. In fact, I observe the same thing on both my R4 and R-388, which also has a 4 ohm headphone output. If you put a 600 ohm speaker across the line it would also be very weak. In any case, the very large difference in gain between what your radio is doing and what is normal does suggest its due to some problem in the audio chain and not just speaker impedance mis-match. If its not the switch in the headphone jack I think you are stuck with the usual routine of checking tube socket voltages and resistances, etc. The output tube is running wide open all the time which may be helpful in tracking down the problem. Someone (Garey?) may be able to supply numbers for normal audio levels in the amp, if so a scope will be helpful in finding the source of trouble. If you don't have Garey's discs I urge you to get them. There is much information there that is not in the Drake literature, such as good photos of the works, plus it gives you clean handbooks and schematics. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
- Original Message - From: ph...@aol.com To: kc9...@aol.com; 1oldle...@ix.netcom.com; drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:46 PM Subject: Re: [Drakelist] My R-4B audio? In a message dated 4/1/2011 7:31:45 P.M. Eastern Daylight Time, kc9...@aol.com writes: Also, just a second thought on the speaker impedance...based on my experience in Audio as well as Ham...one should match the impedance of the speaker to the impedance designed into the audio output circuit While this is generally true, be careful. Some years ago an attempt was made to match a set of low-Z headphones to the 600 OHM HEADPHONES ONLY jack on a commercial audio mixing console using a 600-ohm to 4-ohm audio transformer. Unfortunately, while the transformer may have had an AC *IMPEDANCE* of 600 ohms, the *DC RESISTANCE* of the winding was too low and, over time, it burned out the directly-coupled output transistor in the console by forcing it to source too much current to the load. MORAL: Pay attention to the configuration of the driving circuit before you arbitrarily hang something on the output. 73/Paul, K4MSG Who made this console? Whatever it was the design was plain incompetent. Anyway, the Drake receiver has an old fashioned single-ended pentode amp with transformer coupling. The headphone jack and loudspeaker jack are essentially paralled but the headphone jack has a switch to disable the loudspeaker when headphones are connected. When modern, high fidelity, low impedance phones are connected they are _very_ loud. A pair of 600 ohm phones is about right and even old fashioned very high impedance phones work fine. Neither the amplifier or transformer seem to care about being running into a short or open circuit. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Fwd: My R-4B audio?
Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell -Original Message- From: kc9cdt kc9...@aol.com To: 1oldlens1 1oldle...@ix.netcom.com Sent: Fri, Apr 1, 2011 9:05 pm Subject: Re: [Drakelist] My R-4B audio? BIG UPDATE, I just discovered someone has changed the audio output XFMR! I can tell because they left a small piece of the original secondary wire on the phone jack terminal wher it connects...it is the cloth covered wire. H. who know what it is, if it is correct... Wander if I can find one??? Anyone have one I can buy? That may not even be the issue...if I knwe what the input signal level was supposed to be that would help. 73, Lee -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: Drakelist Drakelist@zerobeat.net; kc9cdt kc9...@aol.com Sent: Fri, Apr 1, 2011 8:00 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: kc9...@aol.com To: 1oldle...@ix.netcom.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:26 PM Subject: Re: [Drakelist] My R-4B audio? Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee The Collins catalogue, to be found on the Collins Collector's site lists the speaker as being 8 ohms. I don't have one so can't measure it. The speakers I have were measured on a General Radio 1603-A Z-Y bridge at both 1 khz and 400 hz. 400 hz is the standard frequency for measurement. There are several things of importance here; first, the impedance of a direct radiator loudspeaker is not constant. It tens to rise at a resonance at the lowe and and also tends to rise at higher frequencies, the two beign for different reasons. The low end rise can be to many times the 400 hz value and will depend on the efficiency of the motor and degree of coupling of the cone. In any case, its typically well below the frequencies of interest for voice communication. The mid-range efficiency also depends on the motor and cone coupling but usually at mid speech frequencies the cone sees a pretty good acoustical impedance match to the overall efficiency in terms of loudness is due mostly to the motor. The more powerful the magnetic field in the gap the louder the speaker will be. This variation can be quite large when comparing cheap, starved magnet speakers with high quality speakers with good magnets. By large I mean ten db. The amplifier in a Drake 4B is a very simple single-ended Class-A pentode stage with no feedback. Such amplifiers tend to have very poor voltage regulation (low damping factor), they are essentially constant current sources. That means the output will actually rise with rising impedance. One result of this is the accentuation of bass resonance in simple enclosures and the tendency to make some loudspeakers sound strident because of their rise in impedance at high frequencies. The mismatch can also increase distortion if excessive. While the total power available may be lower with a mismatch the voltage across the speaker may become higher. The practical effect is that the distortion may become greater at some level. Nonetheless the difference between 4 and 8 ohms should not make a great difference and an 8 ohm speaker may actually be louder. Now, the difference between 4 ohms and 600 ohms is 150 times, that is a lot so one would expect the difference in level to be very great. In fact, I observe the same thing on both my R4 and R-388, which also has a 4 ohm headphone output. If you put a 600 ohm speaker across the line it would also be very weak. In any case, the very large difference in gain between what your radio is doing and what is normal does suggest its due to some problem in the audio chain and not just speaker impedance mis-match. If its not the switch in the headphone jack I think you are stuck with the usual routine of checking tube socket voltages and resistances, etc. The output tube is running wide open all the time which may be helpful in tracking down the problem. Someone (Garey?) may be able to supply numbers for normal audio levels in the amp, if so a scope will be helpful in finding the source of trouble. If you don't have Garey's discs I urge you to get them. There is much information there that is not in the Drake literature, such as good photos of the works, plus it gives you clean handbooks and schematics. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] Fwd: My R-4B audio?
Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell -Original Message- From: kc9cdt kc9...@aol.com To: 1oldlens1 1oldle...@ix.netcom.com Sent: Fri, Apr 1, 2011 8:27 pm Subject: Re: [Drakelist] My R-4B audio? Richard, I agree with whatyou said...I just use the speaker that is called for...I will check more on the Collins.. Maybe they are talking the old A line? Anyways back the PIA problem... OK, UPDATE, ALL voltages on V7 (Final Audio output ) are normal. I replaced the C176 cathode bypass...no help. If I tune in a S9+ signal at 12:00 Audio is ok but not loud enogh...at full open it's louder but distorted (probably to be expected) So, I wish I knew what the P-P signal input of the V7 was supposed to be...wish I had a normal one here...Hi, Hi! I certainly hace a Scope and I have a HP 8640b sig gen. 73, Lee -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: Drakelist Drakelist@zerobeat.net; kc9cdt kc9...@aol.com Sent: Fri, Apr 1, 2011 8:00 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: kc9...@aol.com To: 1oldle...@ix.netcom.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:26 PM Subject: Re: [Drakelist] My R-4B audio? Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee The Collins catalogue, to be found on the Collins Collector's site lists the speaker as being 8 ohms. I don't have one so can't measure it. The speakers I have were measured on a General Radio 1603-A Z-Y bridge at both 1 khz and 400 hz. 400 hz is the standard frequency for measurement. There are several things of importance here; first, the impedance of a direct radiator loudspeaker is not constant. It tens to rise at a resonance at the lowe and and also tends to rise at higher frequencies, the two beign for different reasons. The low end rise can be to many times the 400 hz value and will depend on the efficiency of the motor and degree of coupling of the cone. In any case, its typically well below the frequencies of interest for voice communication. The mid-range efficiency also depends on the motor and cone coupling but usually at mid speech frequencies the cone sees a pretty good acoustical impedance match to the overall efficiency in terms of loudness is due mostly to the motor. The more powerful the magnetic field in the gap the louder the speaker will be. This variation can be quite large when comparing cheap, starved magnet speakers with high quality speakers with good magnets. By large I mean ten db. The amplifier in a Drake 4B is a very simple single-ended Class-A pentode stage with no feedback. Such amplifiers tend to have very poor voltage regulation (low damping factor), they are essentially constant current sources. That means the output will actually rise with rising impedance. One result of this is the accentuation of bass resonance in simple enclosures and the tendency to make some loudspeakers sound strident because of their rise in impedance at high frequencies. The mismatch can also increase distortion if excessive. While the total power available may be lower with a mismatch the voltage across the speaker may become higher. The practical effect is that the distortion may become greater at some level. Nonetheless the difference between 4 and 8 ohms should not make a great difference and an 8 ohm speaker may actually be louder. Now, the difference between 4 ohms and 600 ohms is 150 times, that is a lot so one would expect the difference in level to be very great. In fact, I observe the same thing on both my R4 and R-388, which also has a 4 ohm headphone output. If you put a 600 ohm speaker across the line it would also be very weak. In any case, the very large difference in gain between what your radio is doing and what is normal does suggest its due to some problem in the audio chain and not just speaker impedance mis-match. If its not the switch in the headphone jack I think you are stuck with the usual routine of checking tube socket voltages and resistances, etc. The output tube is running wide open all the time which may be helpful in tracking down the problem. Someone (Garey?) may be able to supply numbers for normal audio levels in the amp, if so a scope will be helpful in finding the source of trouble. If you don't have Garey's discs I urge you to get them. There is much information there that is not in the Drake literature, such as good photos of the works, plus it gives you clean handbooks and schematics. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com
Re: [Drakelist] Fwd: My R-4B audio?
Lee - Since C176 is ok, next is to bridge C173. If the screen voltage is OK on V7, check the voltage on the collector of Q7. Should be around 7 VDC no signal. About 2-3V p-p audio to the grid of V7. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com kc9...@aol.com wrote: Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell So, I wish I knew what the P-P signal input of the V7 was supposed to be...wish I had a normal one here...Hi, Hi! I certainly hace a Scope and I have a HP 8640b sig gen. 73, Lee ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Fwd: My R-4B audio?
Lee - The output transformer is a 2500 to 4 ohm. Probably any small, single tube output transformer will work. The primary current is about 40 mA. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com kc9...@aol.com wrote: BIG UPDATE, I just discovered someone has changed the audio output XFMR! I can tell because they left a small piece of the original secondary wire on the phone jack terminal wher it connects...it is the cloth covered wire. H. who know what it is, if it is correct... Wander if I can find one??? Anyone have one I can buy? That may not even be the issue...if I knwe what the input signal level was supposed to be that would help. 73, Lee Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Fwd: My R-4B audio?
Garey, How would I check to see if that is the correct one in there.. Can I just use a meter and check the resistance on the primary seconday? If it is the wrong one...it could be the problem 73, Lee -Original Message- From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 9:36 pm Subject: Re: [Drakelist] Fwd: My R-4B audio? Lee - The output transformer is a 2500 to 4 ohm. Probably any small, single tube output transformer will work. The primary current is about 40 mA. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com kc9...@aol.com wrote: BIG UPDATE, I just discovered someone has changed the audio output XFMR! I can tell because they left a small piece of the original secondary wire on the phone jack terminal wher it connects...it is the cloth covered wire. H. who know what it is, if it is correct... Wander if I can find one??? Anyone have one I can buy? That may not even be the issue...if I knwe what the input signal level was supposed to be that would help. 73, Lee Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Fwd: My R-4B audio?
- Original Message - From: kc9...@aol.com To: k4...@mindspring.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 6:56 PM Subject: Re: [Drakelist] Fwd: My R-4B audio? Garey, How would I check to see if that is the correct one in there.. Can I just use a meter and check the resistance on the primary seconday? If it is the wrong one...it could be the problem 73, Lee The DC resistance won't tell you much because the size of the wires in the primary and secondary are probably different. You can check the effective output impedance with a varirable resistor and voltmeter. The resistor should be perhaps ten or twenty ohms to cover the range of impedances likely. Get a tone on the RX using the calibrator. With the speaker and headphone jacks open circuited set the level of the output to a convenient level. Now, connect the resistor across the loudspeaker or headphone jack with the voltmeter across it and adjust it for exactly half the voltage you get when open circuited. Now measure the resistance of the pot, that will be the impedance of the output. Since this is the plate impedance reflected into the secondary it will be the correct value of loudspeaker impedance to match the amplifier. If you have an audio oscillator you can measure the turns ratio directly by putting a voltage across either primary or secondary and measuring it at the other end. Voltage varies directly with the turns ratio, impedance with the square of the ratio. Note that transformers do not have a characteristic impedance, they have only a ratio. They are specified to work at certain impedances because the inductance and distributed capacitances will allow a specified frequency range. A transformer can be used over quite wide range of impedances but there will be a change in the low and high frequency cut-off. A variable frequency oscillator and good AC voltmeter can be used to measure the frequency response at various impedances. Output transformers are also designed to handle a certain amount of DC current. The transformer may be the source of the trouble but it would have to be pretty far off. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Fwd: My R-4B audio?
OK, more info... Garey, it is not C173, I bridged it...no change. The voltages I get on Q7 are: .48VDC (Hard to see, but I think it's the base FLAT SIDE OF THE TRANS.) close to 0VDC Base? 18.45 VDC collector? Richard, If I don't find anything else I'll try to check the transformer out per your diredtion. Thanks, Lee -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: kc9cdt kc9...@aol.com Cc: Drakelist Drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 10:35 pm Subject: Re: [Drakelist] Fwd: My R-4B audio? - Original Message - From: kc9...@aol.com To: k4...@mindspring.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 6:56 PM Subject: Re: [Drakelist] Fwd: My R-4B audio? Garey, How would I check to see if that is the correct one in there.. Can I just use a meter and check the resistance on the primary seconday? If it is the wrong one...it could be the problem 73, Lee The DC resistance won't tell you much because the size of the wires in the primary and secondary are probably different. You can check the effective output impedance with a varirable resistor and voltmeter. The resistor should be perhaps ten or twenty ohms to cover the range of impedances likely. Get a tone on the RX using the calibrator. With the speaker and headphone jacks open circuited set the level of the output to a convenient level. Now, connect the resistor across the loudspeaker or headphone jack with the voltmeter across it and adjust it for exactly half the voltage you get when open circuited. Now measure the resistance of the pot, that will be the impedance of the output. Since this is the plate impedance reflected into the secondary it will be the correct value of loudspeaker impedance to match the amplifier. If you have an audio oscillator you can measure the turns ratio directly by putting a voltage across either primary or secondary and measuring it at the other end. Voltage varies directly with the turns ratio, impedance with the square of the ratio. Note that transformers do not have a characteristic impedance, they have only a ratio. They are specified to work at certain impedances because the inductance and distributed capacitances will allow a specified frequency range. A transformer can be used over quite wide range of impedances but there will be a change in the low and high frequency cut-off. A variable frequency oscillator and good AC voltmeter can be used to measure the frequency response at various impedances. Output transformers are also designed to handle a certain amount of DC current. The transformer may be the source of the trouble but it would have to be pretty far off. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
One more thing...non of the voltages on Q7 seem to change as I changes the AF gain Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: Drakelist Drakelist@zerobeat.net; kc9cdt kc9...@aol.com Sent: Fri, Apr 1, 2011 8:00 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: kc9...@aol.com To: 1oldle...@ix.netcom.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:26 PM Subject: Re: [Drakelist] My R-4B audio? Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee The Collins catalogue, to be found on the Collins Collector's site lists the speaker as being 8 ohms. I don't have one so can't measure it. The speakers I have were measured on a General Radio 1603-A Z-Y bridge at both 1 khz and 400 hz. 400 hz is the standard frequency for measurement. There are several things of importance here; first, the impedance of a direct radiator loudspeaker is not constant. It tens to rise at a resonance at the lowe and and also tends to rise at higher frequencies, the two beign for different reasons. The low end rise can be to many times the 400 hz value and will depend on the efficiency of the motor and degree of coupling of the cone. In any case, its typically well below the frequencies of interest for voice communication. The mid-range efficiency also depends on the motor and cone coupling but usually at mid speech frequencies the cone sees a pretty good acoustical impedance match to the overall efficiency in terms of loudness is due mostly to the motor. The more powerful the magnetic field in the gap the louder the speaker will be. This variation can be quite large when comparing cheap, starved magnet speakers with high quality speakers with good magnets. By large I mean ten db. The amplifier in a Drake 4B is a very simple single-ended Class-A pentode stage with no feedback. Such amplifiers tend to have very poor voltage regulation (low damping factor), they are essentially constant current sources. That means the output will actually rise with rising impedance. One result of this is the accentuation of bass resonance in simple enclosures and the tendency to make some loudspeakers sound strident because of their rise in impedance at high frequencies. The mismatch can also increase distortion if excessive. While the total power available may be lower with a mismatch the voltage across the speaker may become higher. The practical effect is that the distortion may become greater at some level. Nonetheless the difference between 4 and 8 ohms should not make a great difference and an 8 ohm speaker may actually be louder. Now, the difference between 4 ohms and 600 ohms is 150 times, that is a lot so one would expect the difference in level to be very great. In fact, I observe the same thing on both my R4 and R-388, which also has a 4 ohm headphone output. If you put a 600 ohm speaker across the line it would also be very weak. In any case, the very large difference in gain between what your radio is doing and what is normal does suggest its due to some problem in the audio chain and not just speaker impedance mis-match. If its not the switch in the headphone jack I think you are stuck with the usual routine of checking tube socket voltages and resistances, etc. The output tube is running wide open all the time which may be helpful in tracking down the problem. Someone (Garey?) may be able to supply numbers for normal audio levels in the amp, if so a scope will be helpful in finding the source of trouble. If you don't have Garey's discs I urge you to get them. There is much information there that is not in the Drake literature, such as good photos of the works, plus it gives you clean handbooks and schematics. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-7 Grid Choke value
On Fri, 1 Apr 2011 16:55:43 -0500, Lloyd wrote: I am repairing an L-7 with and open grid choke ( RFC-1 or 3). Does anyone know the inductance value of these chokes, if so I would sure appreciate letting me what they are. There's a school of thought that suggests that the whole grid choke idea in a 3-500Z circuit is a faulty design decision. I read extensively the comments on both sides of the issue, and decided to remove the chokes and caps, grounding the grids directly to the chassis with copper straps in my L7. I have had no problems to date, the amplifier seems completely stable and tunes up very smoothly. These discussions are out there on the internet, a good search engine should turn up plenty. If you don't get a good answer, I can see if I can measure the ones that I pulled from my L7. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] My R-4B audio?
Garey, I know all you normal people are in bedbut, I'm still working on this. OK, here it is: 40 mtrs, S9+10 signal, AF gain at 12:00, peak to peak is .2 volts?? YES.2 volts not 2 volts. X1 probe...checked with the scope calibratorno question about the level Audio level is ok...Q5 copy but not loud. 73, Lee -Original Message- From: kc9cdt kc9...@aol.com To: 1oldlens1 1oldle...@ix.netcom.com; Drakelist Drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 10:54 pm Subject: Re: [Drakelist] My R-4B audio? One more thing...non of the voltages on Q7 seem to change as I changes the AF gain Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell -Original Message- From: Richard Knoppow 1oldle...@ix.netcom.com To: Drakelist Drakelist@zerobeat.net; kc9cdt kc9...@aol.com Sent: Fri, Apr 1, 2011 8:00 pm Subject: Re: [Drakelist] My R-4B audio? - Original Message - From: kc9...@aol.com To: 1oldle...@ix.netcom.com; Drakelist@zerobeat.net Sent: Friday, April 01, 2011 4:26 PM Subject: Re: [Drakelist] My R-4B audio? Given the same basic design of the speaker (and quality) the 4 ohm one will be louder that 8 ohm. Same for headphones. I have 8 ohm headphones that are lots louder than the 600 ohm ones. Yes, I tried 2 different 4 ohm MS-4 speakers...no difference. Not sure which vintage Collins you speak of but all mine are 4 ohm speakers. I even tried one of those...no diffference. I think I have a issue in the R-4B audio chain...so off to find it.. 73, Lee The Collins catalogue, to be found on the Collins Collector's site lists the speaker as being 8 ohms. I don't have one so can't measure it. The speakers I have were measured on a General Radio 1603-A Z-Y bridge at both 1 khz and 400 hz. 400 hz is the standard frequency for measurement. There are several things of importance here; first, the impedance of a direct radiator loudspeaker is not constant. It tens to rise at a resonance at the lowe and and also tends to rise at higher frequencies, the two beign for different reasons. The low end rise can be to many times the 400 hz value and will depend on the efficiency of the motor and degree of coupling of the cone. In any case, its typically well below the frequencies of interest for voice communication. The mid-range efficiency also depends on the motor and cone coupling but usually at mid speech frequencies the cone sees a pretty good acoustical impedance match to the overall efficiency in terms of loudness is due mostly to the motor. The more powerful the magnetic field in the gap the louder the speaker will be. This variation can be quite large when comparing cheap, starved magnet speakers with high quality speakers with good magnets. By large I mean ten db. The amplifier in a Drake 4B is a very simple single-ended Class-A pentode stage with no feedback. Such amplifiers tend to have very poor voltage regulation (low damping factor), they are essentially constant current sources. That means the output will actually rise with rising impedance. One result of this is the accentuation of bass resonance in simple enclosures and the tendency to make some loudspeakers sound strident because of their rise in impedance at high frequencies. The mismatch can also increase distortion if excessive. While the total power available may be lower with a mismatch the voltage across the speaker may become higher. The practical effect is that the distortion may become greater at some level. Nonetheless the difference between 4 and 8 ohms should not make a great difference and an 8 ohm speaker may actually be louder. Now, the difference between 4 ohms and 600 ohms is 150 times, that is a lot so one would expect the difference in level to be very great. In fact, I observe the same thing on both my R4 and R-388, which also has a 4 ohm headphone output. If you put a 600 ohm speaker across the line it would also be very weak. In any case, the very large difference in gain between what your radio is doing and what is normal does suggest its due to some problem in the audio chain and not just speaker impedance mis-match. If its not the switch in the headphone jack I think you are stuck with the usual routine of checking tube socket voltages and resistances, etc. The output tube is running wide open all the time which may be helpful in tracking down the problem. Someone (Garey?) may be able to supply numbers for normal audio levels in the amp, if so a scope will be helpful in finding the source of trouble. If you don't have Garey's discs I urge you to get them. There is much information there that is not in the Drake literature, such as good photos of the works, plus it gives you clean handbooks and schematics. -- Richard Knoppow Los Angeles WB6KBL dickb...@ix.netcom.com ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-7 Grid Choke value
I do a compromise. When I repair or upgrade the L4, L4B, or L7 linears, I typically remove the grid grounding chokes, put a 33 ohm 1/2 watt carbon resistor to ground from each grid pin, and leave all of the bypass caps in place. Slightly less drive is required with this configuration plus you still have some protection afforded should there be a plate to grid short. Yes, the 0.82 ohm resistor serves this purpose too but an added measure of protection doesn't hurt. Even though the Eimac literature shows the grids grounded directly, thus requiring less drive, I still feel more comfortable with those resistors in place. To each their own, however. 73, Evan, K9SQG -Original Message- From: Jim Shorney jshor...@inebraska.com To: drakelist@zerobeat.net drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 11:15 pm Subject: Re: [Drakelist] L-7 Grid Choke value On Fri, 1 Apr 2011 16:55:43 -0500, Lloyd wrote: I am repairing an L-7 with and open grid choke ( RFC-1 or 3). Does anyone know the inductance value of these chokes, if so I would sure appreciate letting me what they are. There's a school of thought that suggests that the whole grid choke idea in a 3-500Z circuit is a faulty design decision. I read extensively the comments on both sides of the issue, and decided to remove the chokes and caps, grounding the grids directly to the chassis with copper straps in my L7. I have had no problems to date, the amplifier seems completely stable and tunes up very smoothly. These discussions are out there on the internet, a good search engine should turn up plenty. If you don't get a good answer, I can see if I can measure the ones that I pulled from my L7. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Digest Posts
On Fri, 1 Apr 2011 09:52:27 -0500, aci...@gmail.com wrote: Being a lurker and not much of a poster, I can't tell you how pleased I was to see your post regarding quoting. Admirable sentiments, but unlikely to change anything. This battle has been going on for centuries (or so it seems). I really believe that some list members just do it without thinking - It's just SOP for them and they don't think (or bother) to change their email settings when posting. I've come to the conclusion that it's either: A) Laziness, or B) Ignorance (people just don't know that their email program is a mini word processor, or that they can easily highlight and delete text). Some people just make no effort to learn about or follow established netiquette, and nothing will make them do so. And, yes, I also subscribe to the reply first / quote last method because it makes it so much easier to find the wheat. Another endless debate. Personally, I prefer bottom posting. But each method has it's place. The business world prefers top posting because it leaves a clear paper trail of communications. Generally, I prefer bottom posting when only a line or two of text is all that needs to be quoted to convey context. Top posting seems better when a whole block of text is quoted, and trimming too much will tend to lose too much of the overall ideas. Interleaved posting (what I am doing here) is appropriate when commenting on multiple points in a message. In any case, trimming unneccessary text is just good manners. You will forever find evangelical proponents and opponents of each method on the internet, and the arguments will never end. That's why the delete key is mightier than the sword... FWIW, I was recently chastised on another list for not trimming a post, although it is something that I *almost* always do. The one time I don't, and he jumps me. Sheesh Back to Drakes. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-7 Grid Choke value
On Fri, 01 Apr 2011 23:21:01 -0400, K9sqg wrote: I do a compromise. When I repair or upgrade the L4, L4B, or L7 linears, I typically remove the grid grounding chokes, put a 33 ohm 1/2 watt carbon resistor to ground from each grid pin, and leave all of the bypass caps in place. I don't see a problem with that, although W8JI's assertion is that having that grounded grid in between the plate and the cathode offers an extra line of defense against having plate voltage find it's way to the exciter. I think the idea is, which would you rather replace as a result of such an event, a tube or your radio? Considering what a grid is made of, I don't know that it would offer a whole lot of protection. The bottom line for me is that choke/cap is a parallel resonant circuit at SOME frequency, very low in the spectrum. Floating a grid above ground at any frequency where the tube has some gain just seems like a bad idea. Perhaps I'll try the resistor idea in my L-4B. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Fwd: My R-4B audio?
Garey, Yep, I'm still up and working on this baby... OK, one other thing I found: Resistance checks at V7: Pin 6 slowly goes up to 4.8K instead of being 15K like the book says Pin 7 slowly goes up to 4.6K...pretty close to the book I have checked a lot of resisters in both the atrea of Q7 V7 all look pretty good. 73, Lee -Original Message- From: Garey Barrell k4...@mindspring.com To: drakelist Drakelist@zerobeat.net Sent: Fri, Apr 1, 2011 9:36 pm Subject: Re: [Drakelist] Fwd: My R-4B audio? Lee - The output transformer is a 2500 to 4 ohm. Probably any small, single tube output transformer will work. The primary current is about 40 mA. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs www.k4oah.com kc9...@aol.com wrote: BIG UPDATE, I just discovered someone has changed the audio output XFMR! I can tell because they left a small piece of the original secondary wire on the phone jack terminal wher it connects...it is the cloth covered wire. H. who know what it is, if it is correct... Wander if I can find one??? Anyone have one I can buy? That may not even be the issue...if I knwe what the input signal level was supposed to be that would help. 73, Lee Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
