Revitalizing electrolytic caps

[sigint33]

I have an Astron RS-35A power supply that hasn't been used in several years, I'm attempting to use it to power a transmitter, apparently the 2 very large electrolytic caps in it either need to be replaced, (Ac hum on transmit), or I recall reading about a procedure to re-condition electrytic caps after long periods of not being used, can anyone point me in the right direction?<p>sigint33

[ad5mb]

There are 2 ways to do this:<p>1) Get a Variac. Remove tubes, if any. Start at about 85 VAC. Turn the PS on, let it run for half an hour. increase the voltage to 90, turning it up at half hour intervals until you reach powerline voltage, or a little highewr if you are brave.<p>2) The no-variac method. Wire 2 electrical outlets in series. Plug the PS in one outlet, a 600 watt lamp or heater - a resistive load - in the other outlet. Every half hour, substitute a lower-wattage light or load in the other outlet. Then disassemble the series outlet setup before that thing causes problems<p>Either way, you bring the caps up to full voltage in stages.<p>P.S. In Re your handle - were you a Lightning Fast Chicken Plucker? I was a 33D.<p>[ November 22, 2003: Message edited by: ad5mb ]</p>

[sigint33]

Ad5mb,<p>Thanx for your suggestion, if I get ambitious enough I'll give it a try! My handle reflects what I do on a daily basis I design backplanes - signal integrity is a major issue - been working in the backplane industry for 30 years now - designing them for about 15 - I'm not unemployed but I'm not happy where I currently work! - anybody out there looking for a backplane designer?<p>sigint33

[dyarker]

The process is called reforming. It is performed before plugging in a long unused piece of equipment to prevent internal arcing in the electrolytic caps.<p>Since you've already plugged-in the power supply, and the caps didn't blow (literaly) or smoke, there is no internal short. The caps are bad, replace them. Reforming won't help.<p>On ad5mb's method 2; start with the lowwest wattage bulb first (most resistance). 7W, 25W, 40W, 60W, 75W, etc.

[Edd]

sigint33<p>Unfortunately ,electrolytic cap reforming is most successful on higher voltage units , like back in the tube days with 600,450,350 VDC rated units, with minimal results on reforming of low voltage units….especially that units behemoth main filter cap.
I don’t know how hard you were loading the unit on Xmit, but there is one current limiter mod that might help you on current drains on the upper limits …..plus, here is a schematic on your unit if it might have been a Ham flea market find with no documentation. (The mods are marked on the schematic)
(GOOD unit with that old reliable ‘723 in its design.)<p>http://ntc.cap.af.mil/images/rs35a.jpg<p>Being a secure site, the above may/will require a direct entry type in (or cut and paste) and then an ok-yes-yes-then a final zoom in<p>73's de Edd
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<p>[ November 22, 2003: Message edited by: Edd Whatley ]</p>

[sigint33]

Ed!<p>Very valuable post, I could not find a schematic on their web page, I suspect it's not the 2 caps but possiby a problem with the rectifiers, again thanx!<p>sigint33<p>[ November 22, 2003: Message edited by: sigint33 ]<p>[ November 22, 2003: Message edited by: sigint33 ]<p>[ November 22, 2003: Message edited by: sigint33 ]<p>[ November 22, 2003: Message edited by: sigint33 ]</p>

[sigint33]

Sorry about all the edits - I was trying to put my call letters in morse - couldn't make it look right! anyway -<p>DE WB6HHK

[sigint33]

Ed,<p>This schematic appears to be a little weird - on examination some of it makes no sense! - how could TP3 be 13.8V and TP7 0V? - or am I reading it wrong?.<p>sigint33

[sigint33]

On closer examination it appears that the table for A1 is actually a table for the 723, I've found a schematic that matches my unit a little better, but neither one matches it perfectly.<p>Thanx for your help!<p>sigint33<p>[ November 23, 2003: Message edited by: sigint33 ]</p>

[Edd]

Sigint33:<p>You didn’t forward any code dates from components to date your specific units ~ manuf date….since those units have been around ~25 yrs. But I certainly would not suspect deficiencies in its silicon family of semiconductor devices. Instead:
Location-Location-Location…….…or is that……… Elect caps-Elect caps-Elect caps
C1, C5, C4,C101, C8<p>_.-_-._-.. ___.-- _.... _-.-- ___ -._ ---_ -_,<p>……………because it seems HTML is not to friendly in blank space processing, as well
as on ASCII schematics !<p>73's de Edd
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<p>[ November 24, 2003: Message edited by: Edd Whatley ]</p>

[sigint33]

Ed,<p>The unit was bought 12-15 years ago brand new - that would make it logical that the schematic you put here should match it, there are even places on the pcb for the R(number)X modification components, but the schematic that I found using Yahoo dated 11 Jan 78 seems to match it - I may have had a non-problem, I'm lightly loading the supply with a CB so the mods probably won't help, but I noticed the farther I put the receiver that I'm monitoring the output with away from the transceiver reduces the carrier hum. Damn! now I really wish I wouldn't have gotten rid of my old Tek scope when I moved 2 years ago, (couldn't find Nuvistors for it anyway).<p>Sigint33<p>Apparently, my memory is flawed, (surprise!), the date code on the 2n3771 transistors is 9237 that would mean I bought it about 10-11 years ago.<p>[ November 24, 2003: Message edited by: sigint33 ]<p>[ November 24, 2003: Message edited by: sigint33 ]</p>

[Edd]

No, that CB shouldn’t even be tickling that supply. You might check into multi turn power wire routings through ferrite RFI baluns at both ends IF your operating antenna is open and nearby……..not being distant and fed by coax.
Current virgin Nuvistor stock level ~44…Nuvistor sockets… now THAT’s a different story!<p>
73's de Edd
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[sigint33]

Edd,<p>I think your antenna proximity comment is a bingo, I'll play with it this long week-end the antenna is a mobile base load Wilson, (the good one not the mini), and it's located about 6 feet away from the supply with a sheetrock wall in between - on top of the air conditioner condensing unit for my house, (only piece of metal around for ground plane usage), I'm sure it's too close.<p>Mesquite Texas - I lived there for a short period of time, left rather quickly, long hair wasn't fashionable there in the late 60's, LOL!!!<p>Thanx for all your help, as well as everybody else.<p>Sigint33