Re: [drakelist] Interesting End: PS7 Voltage Regulation Problem
Dennis Monticelli [EMAIL PROTECTED] made an utterance to the drakelist gang -- It appears to me that your PS has an undervoltage lockout feature. This is relatively common in today's supplies, but not so when the PS7 was built. Undervoltage lockout turns off the output when the input voltage is insufficient for the PS to work correctly. An incorrectly working supply is potentially dangerous to the load because the output voltage may actually go to a high output state (excessive output voltage) or oscillate. During PS startup, there is special circuitry to insure that the PS is able to ramp itself up rather than get trapped in the undervoltage lockout state. My guess is that the startup circuity in the PS7 is rate sensitive. When you apply full AC instantly, it starts up. When you apply AC input slowly, it does not. Rate sensitive startup (using a capacitor) is usually cheaper to implement than using logic to govern startup. I don't have a PS7 schematic so I admit to some speculation regarding your problem. Dennis AE6C On 3/23/06, Ron Wagner [EMAIL PROTECTED] wrote: Ron Wagner [EMAIL PROTECTED] made an utterance to the drakelist gang -- Kevin, If I understand you correctly, you were only feeding a percentage of the design voltage to the PS7 because of the variac. Let me make a guess as to your problem. The regulator board needs a specified minimum voltage to run correctly. If you were in fact starving the regulator of the correct operating voltage, anything is possible. Anything including the distruction of various components within the regu;lator board, feedback loops in the regulator oscilating, and any number of other strange things. So my guess would be the 723 had its boxers in a bunch and did whatever it pleased and did not get reset until voltages got within specs for the design. 73, Ron -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net -- -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
[drakelist] Drake TR7 problems (x2)
Hi guys. Apologies for posting this on the bulletin board too but I am pulling my hair out. I have two TR7's one which I bought as good the other as known faulty. The good one developed a problem over about a week with the received signal sound getting ever worse and harsh. Then on switch on lights up but no display no received signal even with external VFO - help please where do I look? The other TR7 is unstable on switch on and displays about 17.250 but is ok on the external VFO. After about 20 minutes it seems stable but still occasionally goes off frequency. A quick study of the circuit seems to point to the VCO board - again any help would be appreciated. Dave G0MJK
RE: [drakelist] Interesting End: PS7 Voltage Regulation Problem
Gerry [EMAIL PROTECTED] made an utterance to the drakelist gang -- That sounds about right. It's a question of timing and voltage rise as you bring up line voltage. A DC power supply such as the PS-7 is meant to be turned on all at once. There is really nothing to be gained in slow turn on except for troubleshooting. I have a PS-7 and took it to the bench at work and put it through the ringer. It will do 30 amps continuous if adequately cooled. The transformer uses flat wound copper and looks (at least from what I can tell) to be able to supply at least that much current and more. The only limitations are regulator transistors temperature rise and the bridge rectifier which is rated for 35 amps average forward current and I think either 200 or 400 amps peak surge. At 25 amps, it's loafing. The so-called cooling fan isn't really effective, except for cooling off the enclosure. The forward regulating transistors don't get any airflow due to the construction of the internal frame but it's better than nothing. Incidentally, I did away with the AC connection to the on/off switch inside the TR-7. I'm using a Mother of all DC relays and a wall wart plugged in the fan socket. This required a little rewiring. The wall wart is on all the time but the TR-7 on/off switch activates the big relay DC coil whose contacts are connected to the AC line inside the PS-7. No low-level AC hum in the audio! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wagner Sent: Thursday, March 23, 2006 9:42 PM To: Kevin LaHaie Cc: drakelist@www.zerobeat.net; recipient list not shown: Subject: Re: [drakelist] Interesting End: PS7 Voltage Regulation Problem Ron Wagner [EMAIL PROTECTED] made an utterance to the drakelist gang -- Kevin, If I understand you correctly, you were only feeding a percentage of the design voltage to the PS7 because of the variac. Let me make a guess as to your problem. The regulator board needs a specified minimum voltage to run correctly. If you were in fact starving the regulator of the correct operating voltage, anything is possible. Anything including the distruction of various components within the regu;lator board, feedback loops in the regulator oscilating, and any number of other strange things. So my guess would be the 723 had its boxers in a bunch and did whatever it pleased and did not get reset until voltages got within specs for the design. 73, Ron -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net -- -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
[drakelist] I am selling off my Drake station...
Sterling Garwood [EMAIL PROTECTED] made an utterance to the drakelist gang -- I've retired (finally) and we are downsizing so I need to sell off my Drake station sigh. I thought I'd give the Drakelisters a shot before I throw it to the sharks on ebay. I'd like to sell the TR-7 and R-7 as a pair - if you buy the pair I will throw in the cable to run as a tranceive pair as well as the extender board set (invaluable for maintenance), the MS-7 and the Drake 7077 mic. Right now I am not interested in selling them separately. I have the following: TR-7, R-7, RV-75, MN-2700, MN-7, a non-operational UV-3, extender boards for TR-7/R-7, AUX-7. Condition is as follows: - TR-7 Serial # 8892, some scratches, works fine, needs RCA plugs in back replaced (cracking ceramic) but its usable (I use it every day). has NB-7A + CW filter and AM filter bypass. - PS-7 Serial # 7314, some scratches works fine. - both PS-7 and TR-7 have after market fans. I have the operator manual + maintenance manual (reprints). - R-7 Serial #2883, some scratches, works fine, needs RCA jacks replaced in back (the ceramic is cracking) but it is usable (I use it every day). What is it with the ceramic in these RCA plugs? has a full load of filters (AM, SSB,broad CW, narrow CW)+ NB-7A (or is it the B model - the one with the xtal filter) includes operator and maintenance manuals (reprints). - Wiring harness to use TR-7 and R-7 in transceiver mode. - RV-75 Serial #2777 scratched up cabinet but I also have a new one for it. Also have the RIT jack attachment for TR-7. I have the maintenance manual (a reprint) - MN-7 A bit worn but works. The two lever switches are missing the plastic - like every other MN-7 or MN-2700. - MN-2700 Also a bit worn but works fine (I use it as my main matching unit). Also needs the plastic on the two lever switches. - UV-3 Non operational. Transmits ok but the receive audio is way low. I think its a problem in the audio amp chain. I just haven't found a replacement or had the time to dig into it. I used it daily up to about a year ago. It has a Comspec tone encoder. I have the maintenance manual (actually two) both reprints. I will also throw in two mics with touchpad. One touchpad is bad. - AUX-7 ... not that you need it. I've acquired all this stuff over the last eight years or so ... mostly from ebay and hamfests. Non-Drake stuff - Heathkit HW-8 plus Heathkit power supply for HW-8 for it (was my father's - now an SK). Seems to work (at least it did a year and a half ago). The case is messy, with scratches and so on. - Heathkit Cantenna works fine, full of mineral oil. (I'll drain out the oil.) Prices TR-7/PS-7 $550 R-7 $600 RV-75$600 MN-7 $90 MN-2700 $ 200 UV-3 $100 (remember - its not really usable). AUX-7 $35 HW-8+power supply $30 Cantenna $35 Everything is located in Asheville, NC. If you want further details, pictures, etc ... contact me at [EMAIL PROTECTED] or [EMAIL PROTECTED] S. L. Garwood KJ5AL -- Submissions:drakelist@www.zerobeat.net Unsubscribe:[EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost:[EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net --
