Sparks in el-34 under load?

[JDW3]

I have a Traynor bassmaster, which had been upgraded with some pots and electrolytics. The main filter caps have not been changed.

Under very small load, the tubes are sparking on the inside. Blueish color I believe.

It worked fine for awhile and granted, I don't use it at all. Pull it out every now and then.

Would filter caps be the culprit? The tubes are Mullards and I really don't want to ruin them.

[Blue Strat]

More likely a leaky/shorted bias cap or something else. Check the bias and you'll know. Otherwise, it will continue to be a mystery.

[Swarty]

I assume you've tried different tubes?

[JDW3]

No, I havent tried different ones. I suppose I could pop some in quickly and see. The tubes were fine when I put the amp away. One was brand new (old stock). Its been sitting a few years.

[Blue Strat]

It's a simple test and could eliminate wasted time on everyone's part.