need help with Conrad Johnson preamp SNAFI

Hi folks,
Am seeking tips from wiser heads.

I have a conrad johnson preamp pv10 and a cj power amp premier 11a. I bought the power amp about a year ago. I had the preamp serviced to above-grade condition by one of the names regularly referred to here at the king of CJ repairs and upgrades. Have not used the pair more than 500 hours in the past year.

Anyway, first I turned on the power amp. No problem. Then I turned on the preamp (connected to power amp). As soon as the warm up, the red "bias adjust" lights on the power amp started slowly blinking two at time (the outer two, then the inner two). While that slow blinking happened, a perfectly synced low sound came from the speakers, blurping in time with the blinking lights.

I unplugged the speakers: still blinking. I tried a different preamp and the blinking/blurping on the power amp stopped. But it's a Linn solid state preamp (actually an integrated amp I'm using as a cd/preamp for this experiment). I really really prefer the profoundly musical CJ sound.

After unscrewing about a dozen screws, I opened the preamp up (unplugged of course). No scorching or obvious problems. Umm, I can't tell what a bad tube looks like, and these tubes are really snugly installed. Is there something I should be able to see?

Action item: Should I just buy a new tube complement for the preamp (not a cheap thing, but necessary for the long run if I keep the preamp), try those out, and THEN (if needed) send the preamp to Virginia for repairs?

OR, is this blinking/blurbing phenomenon when the preamp is connected to the power amp NOT symptomatic of a tube problem but of something more electronic (voltage, etc)? I hadn't heard any prior audio problem that could indicate tube degradation.

Thanks for any tips!!