 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
I turned on my Jolida SJ 502A integrated amp this morning. I let it warm up for a few minutes, then I pressed play on my CD player. The moment the music started, I heard a LOUD pop, the left power tube turned very bright, and the only sound coming from my left speaker was a tone/buzz sound.I checked the speaker with another amp, and fortunately it is okay. The left tube now has a burn mark on it like a burned out light bulb. Is this symptomatic of a bad tube, or a problem with the amp? I just bought the Jolida used on eBay last month. I am a total tube novice so don't know how to proceed. I did turn on the amp with no speakers hooked up to it to see if the tube would be burned out, but it turned on like normal. Help please.
Follow Ups:
It seems as if you just went about things in the wrong sequence. Some rules to follow.
1) Never turn the amp on without speakers hooked up.
2) Try to always turn down the volume before firing up.
3) Stick with the sequence for turning on and off the unit.
4) When replacing the tubes in this unit, I would recommend getting a new matched quad as you do not know how old the tubes are and the condition of the 'other pair'. Svetlana 6550 and KT88' are very popular for this unit.
5) Enjoy the music and don't let one off day upset you.Happy listening.
Bill
BG,Kinda sounds like that power tube went ballistic. Was it inherent to the tube or caused by something else? The big question.
What kind of tubes were you using? Does the amp show any signs of previous failures? You may need to look at the circuit boards and wiring to find evidence.
If you have some spare power tubes---you can try another pair (change both tubes on the bad side). But, be sure these are expendable tubes---as the same thing could happen.
You might have a failed bias circuit. Or any number of problems which takes a knowledgable tech to find & fix.
BTW---I usually always keep a load (read: speakers) connected to the output of the amplifier.
Well, I connected the speakers back to the Jolida and just listened to over an hour of music. Everything sounds just fine! Could it be that there was that loud pop, but no serious damage was done? I am beginning to wonder if that burn mark was not on that tube to begin with. Has this ever happened to anyone? Weird. I think I can consider myself lucky.Steven,
I have no extra tubes and know nothing about investigating the circuit boards. Fortunately, it seems that I have escaped major harm...or any harm for that matter. I will post again if it reoccurs...so hopefully this will be my last post. :)
B-loo,Hope for the best. What are the gain stage and phase inverter tubes? I find that some Sovteks and East Euro tubes do the snap, crackle, & pop intially, but settle down after awhile.
If you think that the noise came from the power tubes---I'd keep a close eye on the unit. As a shorted power tube could lead to very bad things, for the rest of the amp.
"If you think that the noise came from the power tubes---I'd keep a close eye on the unit. As a shorted power tube could lead to very bad things, for the rest of the amp."Do you have any specific things to look for? As I said I played it for ...more than 2 hours now, and the sound was great. If the tube is bad, isn't there a way to tell visibly? Would it still light up to the same brightness (or lack thereof) as before the big bang?
My power tubes are Sovtek EL34WXTs. The preamp tubes simply have, in red letters, 12AT7. Actually, only two have that, the other two have nothing on them. I have no idea how old they are.
Sometimes a small particle of metal or oxide will come loose inside a tube and cause a short, but then vaporizes and allows the tube to operate normally again. it seems like you are OK for now, but if this happens again then you should replace the pair of tubes on that side.It might be smart to switch tubes (by the pair) between left and right sides now. Then if the problem recurs and is now on the other side, you'll know it is the tube and not the other circuitry on the original socket.
If there is a loudness imbalance between channels that wasn't there before the incident, then the tube is still bad and should be replaced.
New EL34s are not expensive (about $30 for a matched pair.)
"It might be smart to switch tubes (by the pair) between left and right sides now."Bear with me, as I am very new to tubes. My tubes all have numbers on them that correspond to their position on the amp surface. Are you saying I can swap the right side tubes with the left side tubes without causing damage to the unit?
Also, something I forgot to mention, since I always did this with SS stuff without thinking about it...when I activated the CD player, the volume on the Jolida was set close to the 10 o'clock position (where I had it last night listening for about three hours). Although never a problem with SS, could this pose a problem for a tube amp that was sitting cold overnight with a 5-minute warmup period?
Thanks.
Before pulling any tubes, let the amp cool off for a few hours or overnight (this also discharges the power supply capacitors.)Then switch the output tubes only (the EL34s) between the left and right sides. Keep track of the one that flared up (for example by moving it to the mirror-image position on the other side.) keep the pairs from each channel together.
Pull the tubes out with no more force than necessary, and straight up except for a gentle rocking motion if needed. Push them into their new positions gently until they are all the way down. They should only go in one way, so there is no danger of getting the pins in the wrong holes.
If you have to replace them, Svetlana EL34s and JJ Tesla E34Ls are popular choices. www.triodeelectronics.com and www.thetubestore.com have them, among others.
Good luck!
it might.... I leave my tube preamp on 24/7 (it takes about 20 mins to warm up, otherwise it is rice crispies).
Wow...the things you learn in the owners manual. I just took it out of the box. It says not to turn on the amp without the speakers connected to it "since it may damage the transformers." Oops.Also, the manual suggests a five-minute warm up period...I was real close to five minutes...so that may have been another factor.
And, it also says "other discrete components should be turned on first...otherwise with some equipment, the amplifier will reproduce warm-up thumps, etc., some of which could be harmful to your speaker system." If memory serves, I turned on the CD player after the amp warmed up.
So altogether, I appear to have screwed up royally. But for now, it seems I got away with it.
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
