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.
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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. 
@tvad Sorry, off topic. Tvad, I tried to reply to a dm you sent me and it says you're blocking me. I know that's an error, so just letting you know.
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