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AUDIO FORUMS >> TROUBLESHOOTING >> Tubes, It's Complicated 😡😡
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Message started by HockessinKid on 03/01/26 at 18:56:19

Title: Tubes, It's Complicated 😡😡
Post by HockessinKid on 03/01/26 at 18:56:19

So after installing my new subwoofer, I noticed some tube rush in my left channel of my ZMA. Shortly after this, my left inside bias meter dropped to zero and output in the left channel dropped off considerably. No problem, a new pair of replaced tubes for the left channel and everything is AOK.

Next day still some tube rush in the left channel...huh?? After swapping left to right input tubes it turns out one of my 6N5P was the culprit. So two bad tubes in two days. Thankfully I've got a stash of 5 nice 6NP5 tubes😉

Moralels to the story - sometimes it's two tubes causing problems and always have some back up tubes. Cheers.

HK

Title: Re: Tubes, It's Complicated 😡😡
Post by CAJames on 03/01/26 at 20:12:37

Agree tubes can be complicated. Do you still have the old power tubes? It is possible the only problem was the input tube all along and it just was behaving better temporarily after you turned the amp off to replace the other tubes.

Regardless, good on you for having backups. Being able to swap tubes takes a lot of the frustration out of tube amp ownership.

Title: Re: Tubes, It's Complicated 😡😡
Post by HockessinKid on 03/01/26 at 23:05:59

CAJames,

I changed out the input tubes on the left side of the amp first. The bias meter stayed zeroed out, so the power tube was definitely shot. All is well now, played the amp this afternoon for 3 hours with no hiccups.

HK