Re: [Drakelist] Microphone for 4 line
Yes. Sorry i didnt make that clear. 73 Mark N5KAE___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] Microphone for 4 line
No Problem Mark. I just wanted to make sure all knew there was a different model number for the Dual impedance 444's I've not seen one with any kind of gain pot in them--maybe yet another variation. Curt KU8L On 2/20/2012 9:27 AM, Mark Nace wrote: Yes. Sorry i didnt make that clear. 73 Mark N5KAE *From: * Curt captc...@flash.net; *To: * Mark Nace n5...@swbell.net; *Cc: * drakelist@zerobeat.net; *Subject: * Re: [Drakelist] Microphone for 4 line *Sent: * Mon, Feb 20, 2012 1:16:53 PM That would be the D model I believe.. KU8L On 2/18/2012 10:58 AM, Mark Nace wrote: I have a 444 with a switchable impedance on the bottom. 73 Mark N5KAE *From:* Curt Nixon cptc...@flash.net *To:* drakelist@zerobeat.net *Sent:* Sat, February 18, 2012 9:31:28 AM *Subject:* Re: [Drakelist] Microphone for 4 line Hi John: Any low impedance balanced mic can be used to drive a HiZ input by using one of the small, inline transformers. R Shack, and most music audio stores have them. It must be something wrong in the 444...mine gets excellent reports on the TR4 and and Twins. Maybe just a gunked up connection or dirty switch? Curt KU8L On 2/18/2012 5:55 AM, ko1h wrote: HI all, I just got my R4/t4 pair back from restoration and well my old shure444 isn't getting good reports. I was wondering what microphone currently in production is the consensus to use now? I see replacement elements for the 444 but I'm not sure I want to go that route. Heil used to make a high impedance mic but I don't they do do any longer? What are ya'll using? What do you recommend? Thanks for opinion etc de John ko1h PS if anyone is looking to sell a TR4 in need of slight tlc or just cosmetics please contact me k...@cox.net javascript:return ___ 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 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-4B/L7 Power Supply Rebuilds
A timely question about the L4/L7 bleeder resistors. I recently had an issue with one of my L4PS supplies. It turned out to be a bad cap which I replaced. I'm going to install a Heathkit Shop board eventually but I wanted to get the amp back on line for use in the ARRL CW DX contest. While the supply was open I checked the 50W bleeder resistors and found them both open. I replaced both with new Ohmite resistors. Sunday morning at about 1230Z, one of the new bleeders failed in dramatic fashion by lighting up like a 100W bulb. I quickly swapped in another L4PS and continued on. Last night after the contest I opened up the failed supply to find that the resistors had failed but all other components were all OK (no bad caps, etc.). I replaced the failed bleeder (again) and all was again normal. I'm still quite puzzled as to why this resistor failed in the first place. GL with the project. 73, Stew K3ND From: Dino Papas k...@cox.net To: Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Sent: Saturday, February 18, 2012 2:22 PM Subject: [Drakelist] L-4B/L7 Power Supply Rebuilds I finally bit the bullet yesterday and got around to rebuilding my L-4BPS and L7PS supplies, one with a Heathkit Shop board and the other with the Harbach version. Both procedures went well, with the second going a LOT faster than the first! I will be rebuilding a friend's L-4BPS next week and figured I could minimize the time to do his by working out the bugs doing mine. As my L-4B is my main amp, and based on Evan's note to me a few years ago, I went ahead and changed out the 5K 7W resistor with the 13W version, replaced the 0.82 ohm HV line resistor and the 50K 50W bleeders as a precautionary measure. In the other amp I guess I was just lazy and simply installed only the Harbach board. Now sitting here thinking about it should I go back and just get it over with and replace the resistors in the L7PS? Has anyone ever had a bleeder go bad? Or the others for that matter. Sure, age will wear anything down. Also, the Harbach board doesn't include the diode balancing resistors that Mike's board does...as the original Drake diode strings used 'em what exactly is the difference? Do modern (read that better) diodes still need that protection? I'm just curious. I was pretty impressed that my 32 year old L-4BPS kept going like the Energizer Bunny all these years and I didn't notice any deterioration at all on the bodies of the orange electrolyticsbut, better safe than sorry and I'm looking forward to many more years of reliable operation with both amps. Thoughts? Dino KL0S ___ 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
[Drakelist] low plate voltgage l4b
I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju sent from galaxy tab 10.1 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L-4B/L7 Power Supply Rebuilds
Just like most of us...Age :-) 73, Lee -Original Message- From: GALE STEWARD k...@yahoo.com To: Dino Papas k...@cox.net; Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:30 am Subject: Re: [Drakelist] L-4B/L7 Power Supply Rebuilds A timely question about the L4/L7 bleeder resistors. I recently had an issue with one of my L4PS supplies. It turned out to be a bad cap which I replaced. I'm going to install a Heathkit Shop board eventually but I wanted to get the amp back on line for use in the ARRL CW DX contest. While the supply was open I checked the 50W bleeder resistors and found them both open. I replaced both with new Ohmite resistors. Sunday morning at about 1230Z, one of the new bleeders failed in dramatic fashion by lighting up like a 100W bulb. I quickly swapped in another L4PS and continued on. Last night after the contest I opened up the failed supply to find that the resistors had failed but all other components were all OK (no bad caps, etc.). I replaced the failed bleeder (again) and all was again normal. I'm still quite puzzled as to why this resistor failed in the first place. GL with the project. 73, Stew K3ND From: Dino Papas k...@cox.net To: Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Sent: Saturday, February 18, 2012 2:22 PM Subject: [Drakelist] L-4B/L7 Power Supply Rebuilds I finally bit the bullet yesterday and got around to rebuilding my L-4BPS and L7PS supplies, one with a Heathkit Shop board and the other with the Harbach version. Both procedures went well, with the second going a LOT faster than the first! I will be rebuilding a friend's L-4BPS next week and figured I could minimize the time to do his by working out the bugs doing mine. As my L-4B is my main amp, and based on Evan's note to me a few years ago, I went ahead and changed out the 5K 7W resistor with the 13W version, replaced the 0.82 ohm HV line resistor and the 50K 50W bleeders as a precautionary measure. In the other amp I guess I was just lazy and simply installed only the Harbach board. Now sitting here thinking about it should I go back and just get it over with and replace the resistors in the L7PS? Has anyone ever had a bleeder go bad? Or the others for that matter. Sure, age will wear anything down. Also, the Harbach board doesn't include the diode balancing resistors that Mike's board does...as the original Drake diode strings used 'em what exactly is the difference? Do modern (read that better) diodes still need that protection? I'm just curious. I was pretty impressed that my 32 year old L-4BPS kept going like the Energizer Bunny all these years and I didn't notice any deterioration at all on the bodies of the orange electrolyticsbut, better safe than sorry and I'm looking forward to many more years of reliable operation with both amps. Thoughts? Dino KL0S ___ 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 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] low plate voltgage l4b
Marc, What is your line voltage? 73, Lee -Original Message- From: hs0zju hs0...@gmail.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:53 am Subject: [Drakelist] low plate voltgage l4b I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju sent from galaxy tab 10.1 ___ 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] low plate voltgage l4b
Marc - I just rebuilt the L-7PS with a Harbach board (and a L-4PS with the Heathkit Shop board)Both boards show 2700 volts on the amp meters after putting them into operation. Did you do a low-voltage test before installing? I applied a 20VAC voltage to the input and got ~50VDC at the outputs verifying the voltage doubler function. You may want to give that a trysounds like a part reversal during install. Dino KL0S On Feb202012, at 1050 AM, hs0zju wrote: I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] low plate voltage
Marc, I agree with Lee. Low input voltage. Mine shows 2700 volts running from a 240vac line after rebuild. What do you see in the cw/tune position, lower by the same percentage? Rick W9WS On Feb 20, 2012, at 11:00 AM, drakelist-requ...@zerobeat.net wrote: Send Drakelist mailing list submissions to drakelist@zerobeat.net To subscribe or unsubscribe via the World Wide Web, visit http://mailman.zerobeat.net/mailman/listinfo/drakelist or, via email, send a message with subject or body 'help' to drakelist-requ...@zerobeat.net You can reach the person managing the list at drakelist-ow...@zerobeat.net When replying, please edit your Subject line so it is more specific than Re: Contents of Drakelist digest... Today's Topics: 1. Re: low plate voltgage l4b (kc9...@aol.com) 2. Re: low plate voltgage l4b (Dino Papas) -- Message: 1 Date: Mon, 20 Feb 2012 11:16:17 -0500 (EST) From: kc9...@aol.com To: hs0...@gmail.com, drakelist@zerobeat.net Subject: Re: [Drakelist] low plate voltgage l4b Message-ID: 8cebe021be02ba4-1cb4-1a...@webmail-d062.sysops.aol.com Content-Type: text/plain; charset=utf-8; format=flowed Marc, What is your line voltage? 73, Lee -Original Message- From: hs0zju hs0...@gmail.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:53 am Subject: [Drakelist] low plate voltgage l4b I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts.? 73 marc hs0zju sent from galaxy tab 10.1 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist -- Message: 2 Date: Mon, 20 Feb 2012 11:16:57 -0500 From: Dino Papas k...@cox.net To: Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Subject: Re: [Drakelist] low plate voltgage l4b Message-ID: 5f4823bb-0c60-45c9-9673-9cce13f9c...@cox.net Content-Type: text/plain; charset=us-ascii Marc - I just rebuilt the L-7PS with a Harbach board (and a L-4PS with the Heathkit Shop board)Both boards show 2700 volts on the amp meters after putting them into operation. Did you do a low-voltage test before installing? I applied a 20VAC voltage to the input and got ~50VDC at the outputs verifying the voltage doubler function. You may want to give that a trysounds like a part reversal during install. Dino KL0S On Feb202012, at 1050 AM, hs0zju wrote: I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju -- next part -- An HTML attachment was scrubbed... URL: http://mailman.zerobeat.net/pipermail/drakelist/attachments/ 20120220/422fa7a5/attachment-0001.html -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist End of Drakelist Digest, Vol 44, Issue 38 * ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L4B/L7 Power Power Supply Rebuilds
Stew Based on your description my expectation is that you had a voltage breakdown of the bleeder resistor. While we normally think of resistors in terms of the power they can dissipate, there is a voltage limit that can be sustained across the resistor as well as from the body to ground. I learned this the hard way when I had a transformer fail and ended up replacing it with a P. Dahl transformer with a 10% higher voltage. (3100 V no load, 2950 V load). In that case removed the 2 50K bleeders and installed 10 20k 20W resistors mounted on standoffs, lost a couple of those due to voltage punch through from resistor to chassis before understanding the issue and properly insulating the resistor bodies from the chassis. These particular resistors had about a 2KV breakdown limit through the ceramic insulator to the resistor surface. I don't remember what the actual voltage limit across the resistor was but is the reason that I used the 10 devices in order to keep the drop in the 300V range per resistor as well as keeping the power dissipation in the 5W range, I think around 1K volts was the voltage breakdown limit for the devices I had on hand, but not sure (voltage limit due to power is 630V) . The original Drake 50K 50W bleeders obviously could sustain in the 1500V range across the device, not sure what their rating to ground was, but the power limit is at 1.581KV which I think is pushing them more than needed. The L4PS chassis is not at ground until you hook to the amplifier. So if you have a resistor body that can flash over to ground it will not be apparent until you hook up to the amp. My initial mounting arrangement had the resistors heat sunk to the chassis which turned out to be a dumb idea and was corrected by mounting the resistors on standoffs. I would test the supply out on the bench, worked great then hook up to the amp and experienced quite a light show as the resistors arced to chassis. The above transformer change also required adjusting the bias level due to operating point shift which was done by placing 2 5.6 V zeners in series with filament center tap. This has been working fine now for 8 years. 73 de K5MWR Date: Mon, 20 Feb 2012 07:26:18 -0800 (PST) From: GALE STEWARDk...@yahoo.com To: Dino Papask...@cox.net, Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Subject: Re: [Drakelist] L-4B/L7 Power Supply Rebuilds Message-ID: 1329751578.83763.yahoomail...@web110514.mail.gq1.yahoo.com Content-Type: text/plain; charset=iso-8859-1 A timely question about the L4/L7 bleeder resistors. I recently had an issue with one of my L4PS supplies. It turned out to be a bad cap which I replaced. I'm going to install a Heathkit Shop board eventually but I wanted to get the amp back on line for use in the ARRL CW DX contest. While the supply was open I checked the 50W bleeder resistors and found them both open. I replaced both with new Ohmite resistors. Sunday morning at about 1230Z, one of the new bleeders failed in dramatic fashion by lighting up like a 100W bulb. I quickly swapped in another L4PS and continued on. Last night after the contest I opened up the failed supply to find that the resistors had failed but all other components were all OK (no bad caps, etc.). I replaced the failed bleeder (again) and all was again normal. I'm still quite puzzled as to why this resistor failed in the first place. GL with the project. 73, Stew K3ND ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] low plate voltgage l4b
Typically this is due to low line voltage or a HV meter circuit that needs to be recalibrated. 73, Evan, K9SQG -Original Message- From: hs0zju hs0...@gmail.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:52 am Subject: [Drakelist] low plate voltgage l4b I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju sent from galaxy tab 10.1 ___ 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] L-4B/L7 Power Supply Rebuilds
Stew, The situation you experienced is disturbing. The failures you experienced are strange from several perspectives. Why? Well, first, assuming that the power supply is wired correctly, it is unusual to have both bleeders open. When one experiences a failure mode of open, the series circuit is open and the other resistor has no potential across it, thus no power is consumed and it can't over heat, over current, etc. Second, it is unusual to have new bleeders fail that soon after installation. When replacing the resistors, inspect the mounts for the resistors. The older style uses long bolts with mica insulators at each end while the newer style uses aluminum triangles. If there is any arcing to ground, that can contribute to a failed resistor/circuit. Same for an old, brittle wire that might be arcing to ground. Contrary to popular belief, the 0.82 ohm protection resistor will NOT protect the supply from itself for the most part, just excessive current in the RF deck and/or a short in the connecting cable. Though unlikely, ensure that the line voltage for the amp is not excessive which can stress all components, especially the tube filaments. Whenever I rebuild supplies, I always use one or two fans on top of the supply for cooling purposes. I use hand selected model numbers for 220 v that will start and run reliably on 110 vac, or two 110 vac fans in series, or two 12 vdc fans in series; ultra quiet and reduction of heat is dramatic. Note too that when one of those bleeders opens, it will sometimes arc for an extended period of time before completely opening. The light and smell are unforgettable. Please check the 5K 7 watt resistor on the underside of the supply to see if it too has failed. Please keep us posted. 73, Evan, K9SQG -Original Message- From: GALE STEWARD k...@yahoo.com To: Dino Papas k...@cox.net; Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:29 am Subject: Re: [Drakelist] L-4B/L7 Power Supply Rebuilds A timely question about the L4/L7 bleeder resistors. I recently had an issue with one of my L4PS supplies. It turned out to be a bad cap which I replaced. I'm going to install a Heathkit Shop board eventually but I wanted to get the amp back on line for use in the ARRL CW DX contest. While the supply was open I checked the 50W bleeder resistors and found them both open. I replaced both with new Ohmite resistors. Sunday morning at about 1230Z, one of the new bleeders failed in dramatic fashion by lighting up like a 100W bulb. I quickly swapped in another L4PS and continued on. Last night after the contest I opened up the failed supply to find that the resistors had failed but all other components were all OK (no bad caps, etc.). I replaced the failed bleeder (again) and all was again normal. I'm still quite puzzled as to why this resistor failed in the first place. GL with the project. 73, Stew K3ND From: Dino Papas k...@cox.net To: Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Sent: Saturday, February 18, 2012 2:22 PM Subject: [Drakelist] L-4B/L7 Power Supply Rebuilds I finally bit the bullet yesterday and got around to rebuilding my L-4BPS and L7PS supplies, one with a Heathkit Shop board and the other with the Harbach version. Both procedures went well, with the second going a LOT faster than the first! I will be rebuilding a friend's L-4BPS next week and figured I could minimize the time to do his by working out the bugs doing mine. As my L-4B is my main amp, and based on Evan's note to me a few years ago, I went ahead and changed out the 5K 7W resistor with the 13W version, replaced the 0.82 ohm HV line resistor and the 50K 50W bleeders as a precautionary measure. In the other amp I guess I was just lazy and simply installed only the Harbach board. Now sitting here thinking about it should I go back and just get it over with and replace the resistors in the L7PS? Has anyone ever had a bleeder go bad? Or the others for that matter. Sure, age will wear anything down. Also, the Harbach board doesn't include the diode balancing resistors that Mike's board does...as the original Drake diode strings used 'em what exactly is the difference? Do modern (read that better) diodes still need that protection? I'm just curious. I was pretty impressed that my 32 year old L-4BPS kept going like the Energizer Bunny all these years and I didn't notice any deterioration at all on the bodies of the orange electrolyticsbut, better safe than sorry and I'm looking forward to many more years of reliable operation with both amps. Thoughts? Dino KL0S ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net
Re: [Drakelist] low plate voltage
Rick, Definitive statements can't be made unless the plate voltage meter is known to be in calibration and/or an external meter used to verify its accuracy. 73, Evan, K9SQG -Original Message- From: richard radke rar...@excite.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 12:14 pm Subject: [Drakelist] low plate voltage Marc, I agree with Lee. Low input voltage. Mine shows 2700 volts running from a 240vac line after rebuild. What do you see in the cw/tune position, lower by the same percentage? Rick W9WS On Feb 20, 2012, at 11:00 AM, drakelist-requ...@zerobeat.net wrote: Send Drakelist mailing list submissions to drakelist@zerobeat.net To subscribe or unsubscribe via the World Wide Web, visit http://mailman.zerobeat.net/mailman/listinfo/drakelist or, via email, send a message with subject or body 'help' to drakelist-requ...@zerobeat.net You can reach the person managing the list at drakelist-ow...@zerobeat.net When replying, please edit your Subject line so it is more specific than Re: Contents of Drakelist digest... Today's Topics: 1. Re: low plate voltgage l4b (kc9...@aol.com) 2. Re: low plate voltgage l4b (Dino Papas) -- Message: 1 Date: Mon, 20 Feb 2012 11:16:17 -0500 (EST) From: kc9...@aol.com To: hs0...@gmail.com, drakelist@zerobeat.net Subject: Re: [Drakelist] low plate voltgage l4b Message-ID: 8cebe021be02ba4-1cb4-1a...@webmail-d062.sysops.aol.com Content-Type: text/plain; charset=utf-8; format=flowed Marc, What is your line voltage? 73, Lee -Original Message- From: hs0zju hs0...@gmail.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:53 am Subject: [Drakelist] low plate voltgage l4b I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts.? 73 marc hs0zju sent from galaxy tab 10.1 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist -- Message: 2 Date: Mon, 20 Feb 2012 11:16:57 -0500 From: Dino Papas k...@cox.net To: Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Subject: Re: [Drakelist] low plate voltgage l4b Message-ID: 5f4823bb-0c60-45c9-9673-9cce13f9c...@cox.net Content-Type: text/plain; charset=us-ascii Marc - I just rebuilt the L-7PS with a Harbach board (and a L-4PS with the Heathkit Shop board)Both boards show 2700 volts on the amp meters after putting them into operation. Did you do a low-voltage test before installing? I applied a 20VAC voltage to the input and got ~50VDC at the outputs verifying the voltage doubler function. You may want to give that a trysounds like a part reversal during install. Dino KL0S On Feb202012, at 1050 AM, hs0zju wrote: I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju -- next part -- An HTML attachment was scrubbed... URL: http://mailman.zerobeat.net/pipermail/drakelist/attachments/ 20120220/422fa7a5/attachment-0001.html -- ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist End of Drakelist Digest, Vol 44, Issue 38 * ___ 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] L4B/L7 Power Power Supply Rebuilds
As a side note, a properly wired L4, L4B, or L7 power supply chassis is ALWAYS at ground potential for safety reasons. The safety ground from the outlet goes directly to the chassis of the power supply, whether or not the RF deck is plugged into it or not. A number of years ago, there was a production flaw in the Dale resistors (pitting, gaps, etc. ) in the ceramic that led to flashover on the ends of the resistor. Nit: the L4 power supply used two 100K 50 watt resistors while L4B/L7 supplies typically used 50K 50 watt resistors. -Original Message- From: David Box david_...@comcast.net To: k3nd k...@yahoo.com Cc: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 12:30 pm Subject: Re: [Drakelist] L4B/L7 Power Power Supply Rebuilds Stew Based on your description my expectation is that you had a voltage breakdown of the bleeder resistor. While we normally think of resistors in terms of the power they can dissipate, there is a voltage limit that can be sustained across the resistor as well as from the body to ground. I learned this the hard way when I had a transformer fail and ended up replacing it with a P. Dahl transformer with a 10% higher voltage. (3100 V no load, 2950 V load). In that case removed the 2 50K bleeders and installed 10 20k 20W resistors mounted on standoffs, lost a couple of those due to voltage punch through from resistor to chassis before understanding the issue and properly insulating the resistor bodies from the chassis. These particular resistors had about a 2KV breakdown limit through the ceramic insulator to the resistor surface. I don't remember what the actual voltage limit across the resistor was but is the reason that I used the 10 devices in order to keep the drop in the 300V range per resistor as well as keeping the power dissipation in the 5W range, I think around 1K volts was the voltage breakdown limit for the devices I had on hand, but not sure (voltage limit due to power is 630V) . The original Drake 50K 50W bleeders obviously could sustain in the 1500V range across the device, not sure what their rating to ground was, but the power limit is at 1.581KV which I think is pushing them more than needed. The L4PS chassis is not at ground until you hook to the amplifier. So if you have a resistor body that can flash over to ground it will not be apparent until you hook up to the amp. My initial mounting arrangement had the resistors heat sunk to the chassis which turned out to be a dumb idea and was corrected by mounting the resistors on standoffs. I would test the supply out on the bench, worked great then hook up to the amp and experienced quite a light show as the resistors arced to chassis. The above transformer change also required adjusting the bias level due to operating point shift which was done by placing 2 5.6 V zeners in series with filament center tap. This has been working fine now for 8 years. 73 de K5MWR Date: Mon, 20 Feb 2012 07:26:18 -0800 (PST) From: GALE STEWARDk...@yahoo.com To: Dino Papask...@cox.net, Mail List - Drake Gear Drake Gear drakelist@zerobeat.net Subject: Re: [Drakelist] L-4B/L7 Power Supply Rebuilds Message-ID: 1329751578.83763.yahoomail...@web110514.mail.gq1.yahoo.com Content-Type: text/plain; charset=iso-8859-1 A timely question about the L4/L7 bleeder resistors. I recently had an issue with one of my L4PS supplies. It turned out to be a bad cap which I replaced. I'm going to install a Heathkit Shop board eventually but I wanted to get the amp back on line for use in the ARRL CW DX contest. While the supply was open I checked the 50W bleeder resistors and found them both open. I replaced both with new Ohmite resistors. Sunday morning at about 1230Z, one of the new bleeders failed in dramatic fashion by lighting up like a 100W bulb. I quickly swapped in another L4PS and continued on. Last night after the contest I opened up the failed supply to find that the resistors had failed but all other components were all OK (no bad caps, etc.). I replaced the failed bleeder (again) and all was again normal. I'm still quite puzzled as to why this resistor failed in the first place. GL with the project. 73, Stew K3ND ___ 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] L4B/L7 Power Power Supply Rebuilds
Would agree with you about the input AC power, but if you look at the high voltage the high voltage return side is not tied to the PS chassis but runs to Pin 6 of the power connector and then in the amplifier where it is only tied directly to chassis when the interlock switch is engaged. The interlock switch also shorts the HV to amplifier chassis ground. Under normal operation the high voltage return feeds through the plate current meter and to the center-tap of the filament transformer with a 1ohm 10W resistor to ground, this 1 ohm resistor forms the voltage necessary for the grid current measurement as the grids are tied to chassis and the voltage across this resistor is only due to grid current. This metering arrangement for both plate current and grid require that the HV return not be tied to chassis in either the PS or amplifier. Pin 7 of the power connector is used to tie the PS and Amplifier chassis together. So when you are using just the supply the chassis is at AC power ground but the high voltage return is floating with respect to chassis. With the cable connected to the amplifier there is the meter resistance in series with 1 ohm resistor to ground which is the change that does result in the PS chassis referenced to HV and therefore you can arc the bleeders if you do something stupid like I did of not providing a good HV isolation mount for the bleeders. Playing with these units is not something to be done without a lot of prior thought and making sure you really understand the entire circuit and safety precautions needed. I was probably lucky in not destroying the meter and other parts. 73 de K5MWR On 2/20/2012 11:08 AM, K9sqg wrote: As a side note, a properly wired L4, L4B, or L7 power supply chassis is ALWAYS at ground potential for safety reasons. The safety ground from the outlet goes directly to the chassis of the power supply, whether or not the RF deck is plugged into it or not. A number of years ago, there was a production flaw in the Dale resistors (pitting, gaps, etc. ) in the ceramic that led to flashover on the ends of the resistor. Nit: the L4 power supply used two 100K 50 watt resistors while L4B/L7 supplies typically used 50K 50 watt resistors. -Original Message- From: David Box david_...@comcast.net To: k3nd k...@yahoo.com Cc: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 12:30 pm Subject: Re: [Drakelist] L4B/L7 Power Power Supply Rebuilds Stew Based on your description my expectation is that you had a voltage breakdown of the bleeder resistor. While we normally think of resistors in terms of the power they can dissipate, there is a voltage limit that can be sustained across the resistor as well as from the body to ground. I learned this the hard way when I had a transformer fail and ended up replacing it with a P. Dahl transformer with a 10% higher voltage. (3100 V no load, 2950 V load). In that case removed the 2 50K bleeders and installed 10 20k 20W resistors mounted on standoffs, lost a couple of those due to voltage punch through from resistor to chassis before understanding the issue and properly insulating the resistor bodies from the chassis. These particular resistors had about a 2KV breakdown limit through the ceramic insulator to the resistor surface. I don't remember what the actual voltage limit across the resistor was but is the reason that I used the 10 devices in order to keep the drop in the 300V range per resistor as well as keeping the power dissipation in the 5W range, I think around 1K volts was the voltage breakdown limit for the devices I had on hand, but not sure (voltage limit due to power is 630V) . The original Drake 50K 50W bleeders obviously could sustain in the 1500V range across the device, not sure what their rating to ground was, but the power limit is at 1.581KV which I think is pushing them more than needed. The L4PS chassis is not at ground until you hook to the amplifier. So if you have a resistor body that can flash over to ground it will not be apparent until you hook up to the amp. My initial mounting arrangement had the resistors heat sunk to the chassis which turned out to be a dumb idea and was corrected by mounting the resistors on standoffs. I would test the supply out on the bench, worked great then hook up to the amp and experienced quite a light show as the resistors arced to chassis. The above transformer change also required adjusting the bias level due to operating point
Re: [Drakelist] low plate voltgage l4b
sent from galaxy tab 10.1 On Feb 21, 2012 8:23 AM, funbiz fun...@gmail.com wrote: The line voltgage here is 230volts and is stable when using my ameritron. I just opened the ps to double check my work and it looks 100% Unfortunately i discovered another problem. The cabinet is hot (has voltgage when touched). sent from galaxy tab 10.1 On Feb 21, 2012 1:00 AM, K9sqg k9...@aol.com wrote: Typically this is due to low line voltage or a HV meter circuit that needs to be recalibrated. 73, Evan, K9SQG -Original Message- From: hs0zju hs0...@gmail.com To: drakelist drakelist@zerobeat.net Sent: Mon, Feb 20, 2012 10:52 am Subject: [Drakelist] low plate voltgage l4b I recently aquired a l4b. I upgraded the ps and soft key with harbach. I turned the amp on in ssb with no load and have 2400 volts. I did not try and key or do anything else as i do not want to cause damage. I believe i should have 2600volts. 73 marc hs0zju sent from galaxy tab 10.1 ___ Drakelist mailing listDrakelist@zerobeat.nethttp://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L4B/L7 Power Power Supply Rebuilds
To be on the safe side, bond the amplifier chassis and the PS chassis together with a suitable length of shield from a piece of coax or similar cable. It certainly makes a big difference with the Hallicrafters SR-2000 Hurricane and P-2000 power supply. It is probably not a bad idea with any two piece rig either transceiver or amplifier. 73, John, W4AWM___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] L4B/L7 Power Power Supply Rebuilds
John There is a ground wire in the cable that connects to pin 7 on both PS and amplifier that ties the chassis together. As I understand the metering system of the L4B/L7 you will always have the high voltage return sitting slightly above chassis due to the grid current through the 1 ohm resistor. Thats not much but, you cannot tie the HV return directly to chassis or will lose the metering based on my understanding. Where the real danger can come is if working on the PS independently, you can get in trouble if you make the assumption that the HV return is grounded. Actually when working on the PS you can use a jumper to short the HV return to the chassis which would probably be safer in that TEST configuration and allow you to catch any issues with voltage breakdown due to wire routing or component placement. Playing with 3000 volts at these current levels is a full contact sport and not something for casual or inexperienced operators. This stuff KILLS. 73 de K5MWR On 2/20/2012 7:58 PM, w4...@aol.com wrote: To be on the safe side, bond the amplifier chassis and the PS chassis together with a suitable length of shield from a piece of coax or similar cable. It certainly makes a big difference with the Hallicrafters SR-2000 Hurricaneand P-2000 power supply. It is probably not a bad idea with any two piece rig either transceiver or amplifier. 73, John, W4AWM ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
