BHK 250 Fault Mode/Popping

In the process of trading in my 250 for a pair of 300s, so I switched out the Tungsram 7DJ8s that we’re currently installed back to the factory gold lions.

After the switch:

— the BHK now powers on, then emits a loud pop from the left speaker and then immediately goes into fault mode.

— if I then take the BHK back into then out of standby, no fault mode, but I still get the loud pop from the left speaker when I switch sources on my BHK pre (The Pre has the same Tungsrams as well)

— switched the gold lion out for two other gold lions, with the same result.

—switched back to the Tungsram and everything works perfectly— no fault mode at startup and no popping when switching sources on the Pre.

I would have just guessed it was a bad tube, but for the fact that the issue remain with each other gold lion I tried.

Any thoughts here on what could be the issue? Obviously I could just leave the Tungsrams in for the trade, but would like to figure out the cause, not only for my edification, but also to alert my dealer prior to the trade in if i am not able to troubleshoot.

Thanks in advance,

Is there any chance you mistakenly installed the 12AU7’s instead of 6922? The 250 can only handle 6 volt tubes.

Doh! That’s exactly what I did. I completely had forgotten about the difference in the tubes between the pre and the amp.

Thanks tons—would have spent my evening carefully tearing apart my system trying to figure the issue…

Don’t feel bad, I did the same thing. I took the tube form the box for the tungsram and put it in the amp believing it to be the stock 6922. I bought the amp second hand and I should have checked. As soon as you said what you were experiencing I knew what the issue was. Thank God it does not hurt the amp or anything else. I did order a new set of 6922’s from PS Audio and prefer the sound of them to the tungsrams.

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We have all done these things. :stuck_out_tongue_closed_eyes:

It is amazing the degree to which one’s brain shuts off trying to diagnose the problem, even though it is simple once found.