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AVA Dynaco Super Pas 3 rectifier keeps going bad

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Posted on November 22, 2023 at 20:01:21
JHugh
Audiophile

Posts: 13
Location: Rocky Mountains
Joined: November 16, 2008
 As the subject says, I have a AVA Dynaco Super Pas 3 and the rectifier keeps going bad. I've replaced it at least three times in approximately the last 2 years. I made a note that I last replaced the rectifier on 9/25/2023 and it is now exhibiting the typical issue: I will hear a hissing (or "whooshing") noise after I power up the preamp, then the amp (an Odyssey Khartago). This fades away in about 30 seconds. Days after that, I will notice a dramatic loss of volume in one channel. The last time this happened, I replaced all tubes except the rectifier and there was no change. I replaced the rectifier, kept the new tubes in, and it was back to normal. I replaced the new tubes with the old tubes, keeping the new rectifier, and all was still good. Important: I am not a DIYer, have no skills in troubleshooting. But... what could cause such a problem? TIA

 

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Possibly high voltages at the 12X4, or bad cap(s) in the power supply, posted on November 23, 2023 at 04:54:01
1973shovel
Audiophile

Posts: 10200
Location: Greenville SC
Joined: February 25, 2007
 Those are the first things I'd check for. You say that you don't DIY, but do you own and know how to safely use a voltage meter? The proper voltages are listed in a chart in the original PAS manual.

It's also possible that something in another part of the circuit is drawing excessive current, but I'd start with the voltage checks, and go from there.

If you don't feel comfortable checking voltages, have you contacted AVA to see if they still service the preamp?

Good luck with it.

 

RE: Possibly high voltages at the 12X4, or bad cap(s) in the power supply, posted on November 28, 2023 at 11:26:18
JHugh
Audiophile

Posts: 13
Location: Rocky Mountains
Joined: November 16, 2008
 Thank you for the reply (my reply over the weekend seems to have gotten lost). I do own a voltage meter. Can I safely use it? The honest answer is no. And I can't read a schematic or identify a capacitor or resistor by sight. I haven't called Frank, but his web site still mentions service at $100 per hour. I was thinking $100 could buy 8 or so 12x4s, which could last 50 - 60 weeks. That just masks a problem that might get worse. So yeah, I probably need to make the call.

 

Well, if you're not comfortable taking high voltage measurements..., posted on November 30, 2023 at 12:18:09
1973shovel
Audiophile

Posts: 10200
Location: Greenville SC
Joined: February 25, 2007
 ...I certainly wouldn't encourage you to do so. Good luck tracking down the issue!

 

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