Right channel-music,left-white noise. Help!

[Overhang]

Hello
I have a Thor Audio TA-1000 my Ii. It uses 2 12 ax7 in the input stage and 2 12 at7 on the output. This morning one channel gave out. You can hear only low level white noise coming out of it. All 4 tubes are glowing normally. Any idea what is wrong with it? My other 2 preamps work flawlessly. But this one is my favorite.

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Just to add to my post above: I tried other tubes with the same result. Left channel produces low level white noise. I would assume if it was a fuse the channel would be dead silent. I don’t even know if there are fuses inside since the schematic is impossible to find. Anyone knows a good pro repair in NYC area? I tried Vintage High End with Ben Jacoby but he deals only with Pass units these days

[admin]

If tubes are ruled out then I would go and check all the fuses. The cover may need to come off. Does the manual say where the fuses are located?

Beyond that low hanging fruit I would do a thorough visual inspection looking for any visible damage, ie burn marks, cap swelling, discoloration of components. Without the schematic it will be harder but if you can trace the left channel circuitry that would at least narrow it down.

Just looking at some online pictures of the inside, the layout does not appear to be very complicated so you may be able to identify the bad component.

Unfortunately, I don't have any recommendations in the NY area.

[Overhang]

Looking back,I might have shorted something. I was using CD input only from my DAC and all other inputs had shorting plugs in them. I might have switched the input selector to tape out while the source was playing. Would it explain the damage?also,I noticed that both output tubes run extremely hot and flare up brightly for half a second on power up. I removed all the plugs by now.

[admin]

Shorting plugs "shouldn't" cause any failures but who knows.... I would look inside the unit. If the tubes are hot plating there is a chance you may be able to spot a burned out component.

[SolderSlinger]

A shorting plug on Tape Output, or a second Line out can cause an issue.

[Overhang]

I opened the unit up and could not locate any burn marks or leakage. What I discovered is that one of the 12ax7 tubes (the one in the channel with noise) picks up hum when you hold your hand next to it and hums loudly when you touch it. The other 12ax7 on the working channel doesn’t do it and is quiet no matter if you touch it or not.

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Just want to add that I thoroughly cleaned tube sockets and tube pins and tried numerous 12ax7 tubes in the faulty channel to the same result.

[admin]

Perhaps one of the filter caps has gone bad?

[roberto]

I opened the unit up and could not locate any burn marks or leakage. What I discovered is that one of the 12ax7 tubes (the one in the channel with noise) picks up hum when you hold your hand next to it and hums loudly when you touch it. The other 12ax7 on the working channel doesn’t do it and is quiet no matter if you touch it or not.

Hola,

So if you swap the 12AX7 left channel for the right channel, you still have the same problem in the left side, right? Remove all the shorting plugs in the preamp and try...sometimes shorting plugs are not necessary.

[Overhang]

Did that already to no avail

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My go to guy was Bill Thallman from Music Technology but sadly he passed away and he was the only guy who did tube units. I am hitting the dead end here. I like the pre very much. I tried my back up unit CJ Premier 10 but it’s not even close. The tech guys I knew refuse to take it without schematics and company support. I’m reaching out for a good tech in the Continental US. Anybody knows one?