Overhauling Old HT PSU

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Overhauling Old HT PSU

Postby Proschuno » Thu Feb 13, 2014 11:28 pm

HV PSU schematic.jpeg
HV PSU schematic.jpeg (896.99 KiB) Viewed 1994 times
So I"m overhauling a 50 year old home-builtPSU in serious need of refitting. Using two pass tubes of them has a busted filament and the other was replaced about a year ago. Should I worry about getting a matched pair or just get a single tube?

Also, the circuit uses two oil filled caps that I would like to replace for good measure (along with all the other ones in the schematic). Seeing that these on ebay are quite expensive along with any other electrolytic alternative, I'm wondering if I couldn't simply tie two 450V caps in series as shown for the +B supply? This would be much cheaper than getting another oil cap or similarly rated electrolytic ($US 80 on Mouser).. I notice one of the oil caps' leads is tied before the choke, so I wonder why so?
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Re: Overhauling Old HT PSU

Postby Proschuno » Thu Feb 13, 2014 11:31 pm

And for the missing piece is this, I recovered a little bit when I ripped it out: The OA2 tubes, along with the 1st and 3rd leads of the pot, are in parallel with the 30MF caps, and the cathode of the error amp tube is connected to the center tap of the pot.

And BTW, taking apart the PSU I found the schematic; notice the date…. it's literally as old as my mother lol :))

The pass tubes are 1619 (or VT164), the error amp is 6sj7, the rectifier for +B is 5v4g, and the 2nd one is 6x4.
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HV PSU schematic 2.jpeg
HV PSU schematic 2.jpeg (103.63 KiB) Viewed 1992 times
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Re: Overhauling Old HT PSU

Postby Impmon » Sun May 18, 2014 6:15 pm

With something that old, I'd be most concerned with those electrolytics. The oil filled capacitors are probably OK, unless there's signs of leakage of the oil, or other compromise of the sealing.

It wouldn't hurt to also check out the rest of the components to see if they're still in tolerance.

No real need to match the paralleled series pass 1619s.
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