Tube Replacement Problem - Audio Research SP9 MKiii- V1 Tube Goes Dark w/ new V2 installed


Hi, Does anyone have any suggestions??

I’ve tried replacing the original Sovtek 6922 V2 position tube with a vintage NOS 6DJ8/6922 Amperex SQ circa 1969, but the original V1 position phono tube goes dark and I get no sound from my turntable. The new tube in V2 position works fine and sounds terrific despite the no phono with the darkened Sovtek in V1.

However, when I go back to the original 6922s in V1 and V2 position everything works fine and tubes light as normal. Do the new tubes need to replaced as a matched pair or is there anything else that I should know about replacing a single tube?

The unit is a factory SP9 MKIII.
33andthird

Showing 7 responses by 33andthird

Thank you RJ for the suggestions. I’ve tried all 3 and no luck. Back to the originals and all is working as normal. :( I’m gonna have to have it checked out Bc I’m not a great solder guy. 
Is it safe to touch and pull the tubes while on? I see a couple voltage warnings :O :)
Hi TVad. Thank you. 
The Amperex always works. It’s the others that stop working when the Amperex is put into the mix. 
Then they all work fine under extended use in a separate tube preamp. Hence my bafflement. 
Quick Update @oldhvymec @tvad 

 I’ve cleaned everything and all tubes below work in a separate LS1 preamp as the sole tube. 

Here’s a summary-

SP9 preamp scenario 1- current state-  both sovteks work but I want an amperex in V2 location

SP9 scenario 2 - desired state-  V2 with amperex works, but sovtek in V1 goes dark, no phono

SP9 scenario 3- V1 w Amperex works and phono works, but Sovtek in V2 goes dark and line stages don’t work

SP9 scenario 4- Gold Lion 6922 in V2 works, and Sovtek in V1 works, all sound good from all outputs 

SP9 scenario 5- swapping the Gold Lion locations from scenario 4 and all works and sounds good

Scenario 6 - all individual tubes work fine during extended listening when used in a separate LS1 that has a single tube in the gain stage. As hoped the Amperex sounds best if only I could get it working in a pair in the SP9 :(





Thanks Don. 
If the amperex were dead then why would it be working well in my ARC LS1? It’s been in there a couple days now, glowing and sounding great. 
I did order a new set of tubes from Tube Depot for the SP9 mkiii and look forward to trying them this week.