Using contact cleaner in tube sockets

I have always wondered why ARC neglected to mention in the owner manual that came with the VT50, VT100, Vt100 mkll, and VT200 that when replacing the small driver and input signal tubes they would need to be biased. There is no mention of it at all. Nor is there any mention the difficulty of preforming the biasing of the small signal tubes. It’s nothing like biasing the power tubes. Biasing the power tubes is a cake walk compared to biasing, correctly biasing, the 6922 tubes. Especially the driver tubes.

I would not be surprised if the seller of the OP’s Vt100 knew the new 6922 he bought for the amp and shipped with the amp needed to be biased once installed in the amp.

The reason ARC tubes for the VT100 are so expensive is because each section of each 6922 must be tightly, closely, matched to adjust, set, the bias to within ARC specs. Many tube vendors do not spend the time to match their 6922 tubes that will meet the tightly close matching that is needed. The closer, the tighter, the 6922 tubes are matched the easier it will be to bias the tubes within specs. Even then it can be a PITA. Biasing the 6922 tubes is not for the novice. Lethal DC voltage is present at points the multimeter probes will be connected.



Owner manual. No mention when retubing the 6922 tubes they must be biased.
http://www.audioresearch.com/ContentsFiles/VT100II_Manual.pdf

Could also be a loose pin in the socket. I had that same problem in an Octave V70se and it was loose pins in one socket

For cleaning tube socket female contacts and male tube pins I use  isopropyl alcohol.                                                          


 

jea48

I have always wondered why ARC neglected to mention in the owner manual that came with the VT50, VT100, Vt100 mkll, and VT200 that when replacing the small driver and input signal tubes they would need to be biased ... Biasing the 6922 tubes is not for the novice. Lethal DC voltage is present at points the multimeter probes will be connected.

An owner's manual and a service manual are two different things. As you note, biasing the 6922 tubes is not for a novice. The owner's manual does clearly state: "Refer servicing to your authorized Audio Research dealer or other qualified personnel."

cleeds,

"Refer servicing to your authorized Audio Research dealer or other qualified personnel."

As a rule retubing an amp should not require sending it back to the factory or to a qualified manufacture service center.

ARC should have made mentioned in the owner manual retubing the 6922 tubes required they would have to biased.

There used to be pictures on the Net showing VT100s with burned circuit board traces damage. Just a guess many were due to the user just installing new power tubes and 6922 tubes thinking they only needed to bias the power tubes. If you read the manual what would think?
Look no further than the OP of this thread.

For several years Upscale audio would not sell tubes to owners of ARC VT series power amps. Guys were blowing power tubes and damaging their amps and blaming it on the tubes Upscale audio sold them.