Bias way off should at most have a tube burning very brightly. I can't see a tube blowing so quickly from a high bias. Time to take it to a shop to check for a problem somewhere...
11 responses Add your response
If it is a new unit, call Mike at Jolida. They will promptly replace it with a new one. I had a similar problem with their CD player a few years ago. It worked for a day then started skipping on every disc. Mike sent me a new one via FedEx next day and I sent the other one back the next day at no charge to me. First class outfit.
I sure hope it is just a bad tube and not something with the "guts" of the amp. I purchased it from EBay, the outer shell is in mint condition and the seller did a heck of a job with the packing, it was well taken care of.
Thanks for the replies, I'll report back when I install the replacement tube.
"I was able to turn two pots several revolutions without reaching the stop point."
Normal for multiturn bias trim pot, which the newer Jolida units has. Bias should have been checked after shipping before power up.
The multiturn pots make for more precise setting unlike the older single turn ones.
When replacing the tube make sure and turn the pot down several revolutions, it's a 12 or 13-multiturn pot.
Tubes can fade away or die spectacularly, both of which has happened in my 502p with no issues issuing from the amp. That's tubes for ya. A note on Shubert's post...I love my NOS UK origin Mullard 12AT7s, but I've had really good luck with Russian Gold Lion 12AX7s and KT120s, 150s, various new Tung Sol and EH stuff, Mullard reproductions (in my class A 18 watt guitar amp), JJs, etc., and I think you can learn a lot more from fooling around with tubes than paying much attention to fools around tubes.
Awesome news gents, it was indeed the tube, the new one arrived today, and the amp is purrin along as I type.
A bias check revealed numbers in the 500-550 range and not the recommended 400mv. I dig the easy bias feature and the heavy duty remote control, over all a well built amp.
BTW Mike at JOLIDA is helpful dude.
Happy in Houston.
My 502 has been cookin' along with new Gold Lion 12AX7s and KT150s for a couple of weeks now and I'm astonished at how good it sounds now that things have settled in even more...I've recently listened to some far more expensive stuff including an ARC REF 75 and a Rogers integrated (although not in my home system), and man...made me realize how good my little 502 really is.