Advice on Repairs for Audio Research VT100 Mk II

Did you or the guy you bought this amp from install new 6922 tubes in the Amp?

Or maybe did the guy you bought the amp from pull all the tubes from the amp for shipping? If yes each tube would have to have been marked for each tube socket they were removed from and reinstalled in the same tube sockets they were removed from...

Thanks again to everyone who responded. The tubes were already installed when I bought it and I had a car share and a short drive, so I didn't bother removing the tubes for the drive home. I think he said that the tubes were fairly new. It was my first tube amp, so I didn't know which questions to ask. The former owner is actually really helpful and offered to help pay for the repair if I get the work done at the tech shop here in Berlin that he regularly uses. I however wanted to get it done at the authorised dealer in Hamburg, which he considers to be overpriced.

Some responses above have suggested eating the costs and moving on, but that would mean selling the amp as defective and I wouldn't expect to get more than EUR 500 for a defective amp. That would mean a loss for me of EUR 2,000. Or do you think I could get maybe EUR 1,000?

So, at this point I think I will either bite the bullet and get it repaired at the ARC authorised dealer or have it sent back from Hamburg (which is another EUR 100) and get it fixed by the tech guy here in Berlin recommended by the former owner. I just don't feel like lugging this beast around any more. I don't have a car, so moving it always entails doing a car sharing or taxi/Uber.

I also sent an email to ARC as suggested by some of the posters, so we'll see how they respond. 

Since you mention that it is your first tube amp I want to mention that hopefully you are aware that you should not turn a tube amp on and off and back on quickly without giving the capacitors a couple minutes to discharge.  That can lead to problems such as you describe.

According to the schematics the VT 100 MKII is a fully balanced design. The offset between pos and neg branch needs to be set to 0 and that's taken care of by some ss circuits between the 6922 (some adj. can be made with RV1/RV2 trim pots).

The 6922 are double triodes and it's of course harder to match those tubes because you need a lot of them in order to find 4 tubes per channel where the two triodes in each tube are also about the same quiescent current. That makes it time consuming and expensive. In general Audio Research biases  their output tubes very hot and they need a lot of tubes to select from in order to reach those goals. That's why it is so expensive if you go to Audio Research for retubing.

Many things can go wrong if one tries to do this buying tubes (even matched) somewhere else unless one fully understands how this amps work. Schematics are available online.

To use the VT100 only makes sense IMO(considering the high cost) if one uses  a fully balanced system (at least preamp to amp).

Since you mention that it is your first tube amp I want to mention that hopefully you are aware that you should not turn a tube amp on and off and back on quickly without giving the capacitors a couple minutes to discharge.  That can lead to problems such as you describe.

I think I did do that a couple times because I was following another rule that someone told me: always turn on the source (DAC/pre-amp) before turning on the amp. Once or twice I forgot about this and turned on the amp first, so then I turned it off, turned on the DAC/pre-amp, and then turned the amp back on. Doh. 

I had a VT 100, MK III and loved it.   So my comments are based on experience with that particular iteration.
 

Probably, you’ll want a tech to replace the resistor and test to ensure that everything is copacetic.  
 

But it doesn’t take much skill to replace and bias the tubes yourself.  Bias adjustment instructions can be found at the Audio Research Database (arcdb.ws I believe), so you can read it and see how comfortable you are with the procedure.  
 

You can buy a package of matched tubes specifically for your amp at the Tube Store.  They have good selection and pricing, and their customer service is excellent.

I used to retube and bias mine in about an hour.  It’s a wonderful amp and I’d hate for you to give up on it.