Advice on Repairs for Audio Research VT100 Mk II

It's a fact of life that most tube amplifiers require periodic maintenance and ARC is no exception. I don't think it makes sense to quibble with your tech any more than it makes sense to quibble with your mechanic. Some ARC owners are comfy swapping their own tubes and replacing resistors themselves and that's a fair approach. But once someone is selected to do the job, they should be paid for the work they specify. That way, if there's an issue later, the burden is on them. And at the same time, you've shown them the respect they deserve. If you want the work done cheaper, you're free to take it elsewhere.

Cleeds is right. WTS, you are half in already, so I would ask myself did the amp fit my system and would it be a long term fit that I can live with, if not sell and move on, if it is a keeper then bite the bullet and do the repairs and live happily ever after. BTW those prices for the 6922 are really steep. Enjoy the music

@edward78 said:

I’m fine with the price of the resistors, 6550 tubes, and labour but the price for the 6992 tubes seems too high. On the JJ Tubes website, these tubes sell for about EUR 20 a piece and they do not even offer matched sets of 6992. Do the 6992 input tubes really need to be matched?

The VT100 and Vt100 MK II are good sounding amps. But they are not user friendly when it’s time to retube the 6922 signal tubes. The average audiophile is not qualified to bias the 6922 signal tubes. If not done properly, biased within ARC specs, damage will done to the amp. It can damage power tubes, will cause power tube(s) screen resistor(s) to blow. That can damage circuit traces when the resistor(s) blow.

Do the 6992 input tubes really need to be matched?

Not just matched... Both sections of the 6922 tubes must be tightly, closely, matched... Especially the driver 6922 tubes. IF not tightly, closely, matced it will be impossible to set the ARC spec bias voltage within specs.

Link Below will show you just how involved it is to bias the 6922 to ARC’s specs.

http://mycollins.net/audio/artube1.html

ARC complete retube bias instructions:

https://www.arcdb.ws/Database/VT100/ARC_VT100MKII_bias_adjustment.pdf

FWIW: Not every tube vendor out there will take the time to sort through umpteen 6922 tubes to find tubes that have tightly, closely, matched Triode sections. Close won’t get it!.. Even if the sections are tightly, closely, matched the tech may still spend hours moving the 6922 tubes around to bias the tubes to meet the specs for each channel of the amp.

I don’t know how much you paid for the amp, but you may want to buy something else.

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Yikes.

13 hours of time seems excessive for the damage. The resistors were damaged by the power tubes FWIW. Its reasonable to expect that every time a power tube fails a resistor could be damaged- and so will need another trip back to the shop...

If the tubes are really that difficult to match, I'd be looking elsewhere- this amp sounds like a liability.

You could try reaching out to ARC service department. They have been very responsive and helpful in my experience.