My amp (JCM800KK) this morning ceased to work. It makes no sound whatsoever. No hiss, no pop, nothing. I don't think it's a cab problem. My drummer tried to look inside and he says seems like one tube is not glowing at all. I didn't feel like I wanted to remove the grid, I have no knowledge to put my hands inside.
What could it be? Is that something I can fix myself?
Re: Tube amp is dead
2Does it turn on at all?
No sound at all, like no hiss or anything, could be power tubes, a bad output impedance selector switch or output jack, bad output transformer, or something wrong in the power supply.
No sound at all, like no hiss or anything, could be power tubes, a bad output impedance selector switch or output jack, bad output transformer, or something wrong in the power supply.
Re: Tube amp is dead
3Yes it does.
Sounds like bad news.Nate Dort wrote: Sun May 23, 2021 2:08 pm No sound at all, like no hiss or anything, could be power tubes, a bad output impedance selector switch or output jack, bad output transformer, or something wrong in the power supply.
Thanks for your help.
Re: Tube amp is dead
4If you are not comfortable with working on this yourself - and it sounds like you're not and I'm glad that you recognize that. The best thing you could do now would be to keep the amp turned off and find a reliable amp tech in your area. If you do have a problem with an impedance selector switch or output jack as Nate has suggested as possibilities - those are probably cheaply and easily fixed. If those are the problems and you keep the amp on with no load on your output transformer, you could and likely would turn a cheap easy fix into an expensive one. Don't stress about it - whatever damage is done is done and I would bet that the vast majority of your amp is still functioning and can be brought back to life for far, far less money that you would need to invest in getting a new amp.
If you do want to learn about your amp and how to fix it - that's totally possible too and I'm sure you're intelligent enough to figure it out. However, that probably won't happen in a hurry.
Here's a pretty good tube amp debugging method.
MAKE SURE TO READ THE SAFETY WARNING AND DISCLAIMER. IT COULD SAVE YOUR LIFE.
http://www.geofex.com/ampdbug/ampdebug.htm
If you do want to learn about your amp and how to fix it - that's totally possible too and I'm sure you're intelligent enough to figure it out. However, that probably won't happen in a hurry.
Here's a pretty good tube amp debugging method.
MAKE SURE TO READ THE SAFETY WARNING AND DISCLAIMER. IT COULD SAVE YOUR LIFE.
http://www.geofex.com/ampdbug/ampdebug.htm
Re: Tube amp is dead
5Thank you so much for the advice and for the link.GussyLoveridge wrote: Sun May 23, 2021 11:17 pm If you are not comfortable with working on this yourself - and it sounds like you're not and I'm glad that you recognize that. The best thing you could do now would be to keep the amp turned off and find a reliable amp tech in your area. If you do have a problem with an impedance selector switch or output jack as Nate has suggested as possibilities - those are probably cheaply and easily fixed. If those are the problems and you keep the amp on with no load on your output transformer, you could and likely would turn a cheap easy fix into an expensive one. Don't stress about it - whatever damage is done is done and I would bet that the vast majority of your amp is still functioning and can be brought back to life for far, far less money that you would need to invest in getting a new amp.
If you do want to learn about your amp and how to fix it - that's totally possible too and I'm sure you're intelligent enough to figure it out. However, that probably won't happen in a hurry.
Here's a pretty good tube amp debugging method.
MAKE SURE TO READ THE SAFETY WARNING AND DISCLAIMER. IT COULD SAVE YOUR LIFE.
http://www.geofex.com/ampdbug/ampdebug.htm
Yesterday I couldn't figure out what the problem was and was stupid enough to try to turn it on again a couple of times... I hope I haven't done more damage.
Yes, I'm that stupid.
Re: Tube amp is dead
6If it turns on but makes no sound at all its very likely that you blew a fuse on the high voltage supply. The amp turns on because the mains fuse is intact and the filaments of the tubes work and light up. On that amp, however, the secondary fusing is all internal (and possibly hard-wired direct to the board), so as previously directed get a tech to check it out.
The question is what caused the fuse to blow, and if your drummer was correct and one tube was not lit-up, then it seems likely to me that you just killed a tube which is bound to happen from time to time. Fortunately the amp should be properly protected so that when that happens it doesnt damage anything important.
The question is what caused the fuse to blow, and if your drummer was correct and one tube was not lit-up, then it seems likely to me that you just killed a tube which is bound to happen from time to time. Fortunately the amp should be properly protected so that when that happens it doesnt damage anything important.
Re: Tube amp is dead
7thank you so much.Dr Tony Balls wrote: Mon May 24, 2021 8:47 am If it turns on but makes no sound at all its very likely that you blew a fuse on the high voltage supply. The amp turns on because the mains fuse is intact and the filaments of the tubes work and light up. On that amp, however, the secondary fusing is all internal (and possibly hard-wired direct to the board), so as previously directed get a tech to check it out.
The question is what caused the fuse to blow, and if your drummer was correct and one tube was not lit-up, then it seems likely to me that you just killed a tube which is bound to happen from time to time. Fortunately the amp should be properly protected so that when that happens it doesnt damage anything important.
Are these costly repairs? It's the first time I have a problem with my amps, never had to have them repaired before...
Re: Tube amp is dead
8No clue. If it really is a bad tube, then you're likely looking at a new quad of EL34s (~$70) plus the labor to troubleshoot that, change the fuse, and re-bias (maybe an hour?).oZZma wrote: Mon May 24, 2021 9:13 am Are these costly repairs? It's the first time I have a problem with my amps, never had to have them repaired before...
Re: Tube amp is dead
9I was also thinking the HT fuse. I took a look at the KK signature head, and unfortunately the HT fuse is not accessible from the outside.
The amp use KT88 power tubes. A little more that EL34s,cost wise.
It seems like a pretty standard fix for an experienced tech.
The amp use KT88 power tubes. A little more that EL34s,cost wise.
It seems like a pretty standard fix for an experienced tech.
Re: Tube amp is dead
10benadrian wrote: Mon May 24, 2021 11:39 pm I was also thinking the HT fuse. I took a look at the KK signature head, and unfortunately the HT fuse is not accessible from the outside.
The amp use KT88 power tubes. A little more that EL34s,cost wise.
It seems like a pretty standard fix for an experienced tech.
thanks a lot guys.Dr Tony Balls wrote: Mon May 24, 2021 9:32 amNo clue. If it really is a bad tube, then you're likely looking at a new quad of EL34s (~$70) plus the labor to troubleshoot that, change the fuse, and re-bias (maybe an hour?).oZZma wrote: Mon May 24, 2021 9:13 am Are these costly repairs? It's the first time I have a problem with my amps, never had to have them repaired before...
KT88 is the type of tubes and there are many brands for the same type, is it correct? What brand are the stock ones? Any idea? My fear is that the sound may change.