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Hello y'all,

I've been having a problem with JVM 205Combo.
During corona-lockdown, when we were not allowed to rehearse with the band, I had took my amp home with me....
As I'm always curious to find other sounds, I started experimenting with connecting other speaker cabs to my JVM. But, as I later discovered, the cable I used was no good and I think I blew up the main amplifier. I looked for the fuse, for it seemed logical to me that the fuse was blown, but couldn't find it. I also have a JCM 800 2205 head, a JMP MK2 2204 head and I've been having a JCM900 4100 head in the past. Now, all these amps were fused, so if anything went wrong, it was just the fuse that was blown. In fact, I've experienced that!
But no fuse on the JVM....is that correct? Because if it is, my problem is bigger than I thought. In that case, what was blown instead? The output transformer? My tubes?

I hope somebody can help me out on this one. And I promise never to experiment with other speakers or whatsoever.

Thnx anyway!
Cheers!

 

asked 10 Sep 2021 at 08:23 PM

Arno Visser
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Hey Mates,

 

Having issues with a clients amp, seems that after a retube that i did, he was playing and after about 30 min, it gradually started losing sound and then cut sound completely.  I did the re-tube myself, and biased it properly and i was able to play it for about 40 min with absolutely no issues.  List of troubleshooting steps i have done:

tried a different speaker cable

tried a different guitar cabinet

tried a different guitar and guitar cable

tried the old tubes, additionally bought a 12ax7 and tested each pre-amp tube

tried a different power source

Have tried different power tubes

have checked and replaced the fuses

 

Now this is what i am THINKING is the problem, I think it might be something with either the heater curcuit fuse, or i think it's called a BRT1 Rectifier?  I did alot of research and it seems that the people having MY issue, explain the same symptoms of what i am having.

 

Now i have to make this clear, I AM NOT A PROFESSIONAL TECH, just a guy helping bands out with tech stuff that they don't know how to do.  So any help is appreciated.

 

Thanks!

asked 27 Jun 2019 at 08:01 PM

Austin Hetrick
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My J60 tube amp made a loud POP while jamming. All the tubes are secure and lit up, and the fuse still looks good. The amp isn’t making any sound at all though. Any suggestions on what might be the problem?

asked 21 Mar 2019 at 12:43 PM

Zachary Daniels
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I have looked for a definite answer to this and have not found one. I played my amp the other night with no problems, but last night as I turned on the amp it just died on me as soon as I turned the standby off. There was no noise, pops, crackles, fizzes. It just turned off. I checked the main fuse and it was blown. I have not had any issues with tubes and they have not shown any signs of wearing out. I made sure my amp was connected to the cab correctly (remember i have had this rig for 8 years) and that I had a speaker cable rather than a guitar cable.  I found online there could be issues with impedence and what not. I took the back off of my cab and noticed that a positive lead on one of my v30's became disconnected.  I thought, 'Could it be?" So I reconnected it and replaced the fuse and the amp worked as advertised. I played for an hour or so and no problems yet. Could it be that the discoonnected positive lead on one speaker caused it to blow a main fuse?

asked 11 Apr 2017 at 03:11 PM

David Bradley
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