Audio Research VT100 MKII retubing blew resistors

I was trying to retubing input tubes in my Audio Research VT100 MKII amplifier. I changed old Sovteks 6922 with JAN Sylvania 7308 tubes. Now I have my amp damaged.

I will describe all my steps:

1. I was replacing input and driver tubes – your originally Sovteks ended their life. I have used Sylvania JAN 7308 tubes.

2. I replaced small tubes and after few swapping I calibrated it closely step by step with ARC procedure and achieved quite good measurements falling within all tolerances. Imbalance at +160 VDC point was less than 10 Volts in both channels.

3. After finishing small tubes calibration I have installed original 6550C power tubes from ARC which worked fine before. Before I started biasing power tubes loud noise and flame appeared and one of the resistor blew and turned into a pieces. (But it was not the power tube biasing resistor). Those flame caused burning second resistor placed next to the first.

4. Broken are two vertical resistors 100 ohm and 1 ohm placed on the right side next to V12 power tube socket. One is black carbon type marked PRC SM186 100 +/- 5% (that blew first), and second is brown resistor marked with gold and blue strips placed vertically next to those black. I also have damaged (braked) the signal path under those resistors.

5. I would like to mention that resistors blew not right after powering on the amp with power tubes installed but after about 15 seconds of warming up. So probably it was not the normal short circuit.

6. Before installing the tubes I cleaned up the sockets first with polypropylene alcohol and after that treated tube pins with Caig’s DeoxIt Gx contact enhancer. I am wondering if the rests of alcohol could be a reason of fire? I have cleaned the sockets about two hours before installing the tube and the alcohol should evaporate. I also do not thing if I could use DeoxIt so extensive to make short-circuit on the V12 tube base.

And now my questions:

- Is it possible that after achieving every measuring points within tolerances that input tubes still causing resistors damage?

- Can I still try swat the input tubes with hope to get good results, or should leave those Sylvanias and look for something else?

- Is the power tube from the socket where resistors blew still usable? How to check it in another way than just trying?

Best regards,
Milimetr