Marshall JCM2000 DSL100 volume loss,HELP!

[mojavemarshall72]

Hello,
My name is Tony and I have a problem with my JCM2000.
I had a problem with the volume cutting out altogether but sometimes if I
played with the volume pots it would come back on. Just to be safe I re-tubed the entire amp and biases it of course. Haven't a problem in over a month
now. Today I was playing about 2 hours with my drummer and same thing happened. Compete loss of volume(not gradual complete cut out). Anybody know of a cause here. I am desperate as I have a big gig on Thursday night in Philly. Any and all help is appreciated!
Thanks,
Tony Mac

 

[joepete77]

I had problems like that with a dsl I had yrs ago. I retubed it and the problem would go and come still. The volume would swell in and out but only when amp was hot after about 30 min playing.When volume would drop out, if I turned amp off and on it would shortly be normal again. It turned out to be a problem with the diode rectifier along with some cold solder joints on board that would give when amp was heated up after time.

 

[joepete77]

If the volume is sharply cutting off but amp still has power light on, make sure you check the simple things first like speaker cable, input jacks, speaker jacks , etc.

 

[mojavemarshall72]

If the volume is sharply cutting off but amp still has power light on, make sure you check the simple things first like speaker cable, input jacks, speaker jacks , etc.

 

[mojavemarshall72]

I had problems like that with a dsl I had yrs ago. I retubed it and the problem would go and come still. The volume would swell in and out but only when amp was hot after about 30 min playing.When volume would drop out, if I turned amp off and on it would shortly be normal again. It turned out to be a problem with the diode rectifier along with some cold solder joints on board that would give when amp was heated up after time.

 

[tweed]

These amps are notorious for the speaker jacks getting whacked out. There is a simple mode you can do that involves soldering one wire across the jacks. This will explain it better. My DSL had this issue, performed this mod and haven't had an issue since.

"The rear board on these amps has a major design flaw: The ground connection to the 4 and 8 ohm speaker jacks is switched through the 16 ohm jack. When nothing is inserted in the 16ohm jack, the ground connection to the other jacks is made. The big problem with this is that the switched jack connection, with time, will always get dirty, end up not closing properly and in some case, just outright fail."


http://www.marshallheads.com/viewtopic.php?f=8&t=48

 

[mojavemarshall72]

These amps are notorious for the speaker jacks getting whacked out. There is a simple mode you can do that involves soldering one wire across the jacks. This will explain it better. My DSL had this issue, performed this mod and haven't had an issue since.

"The rear board on these amps has a major design flaw: The ground connection to the 4 and 8 ohm speaker jacks is switched through the 16 ohm jack. When nothing is inserted in the 16ohm jack, the ground connection to the other jacks is made. The big problem with this is that the switched jack connection, with time, will always get dirty, end up not closing properly and in some case, just outright fail."


http://www.marshallheads.com/viewtopic.php?f=8&t=48

 

[MississippiMetal]

These amps are notorious for the speaker jacks getting whacked out. There is a simple mode you can do that involves soldering one wire across the jacks. This will explain it better. My DSL had this issue, performed this mod and haven't had an issue since.

"The rear board on these amps has a major design flaw: The ground connection to the 4 and 8 ohm speaker jacks is switched through the 16 ohm jack. When nothing is inserted in the 16ohm jack, the ground connection to the other jacks is made. The big problem with this is that the switched jack connection, with time, will always get dirty, end up not closing properly and in some case, just outright fail."


http://www.marshallheads.com/viewtopic.php?f=8&t=48

This. when I first bought a DSL, it had the exact same issue you're describing, and after I did the speaker jack mod just for general purposes, the issue went away. I've since cured the same symptoms you describe by performing this mod on about a dozen other DSL100's.

The issue here is that the sleeve connection on the 4/8 ohm jack gets its chassis ground reference by way of the 16 ohm jack's switching sleeve contact. If the 16 ohm sleeve switch connection gets dirty, or for whatever reason loses proper contact, the 4/8 ohm jacks no longer have a ground connection, and this causes your output issue. It can also cause other symptoms, but yours seems to be the most common. The mod basically entails hard soldering a strip of bus wire across all sleeve terminals to ensure chassis ground connection for all jacks at all times.

Hope this helps.

 

[Ardissy]

These amps are notorious for the speaker jacks getting whacked out. There is a simple mode you can do that involves soldering one wire across the jacks. This will explain it better. My DSL had this issue, performed this mod and haven't had an issue since.

"The rear board on these amps has a major design flaw: The ground car navigation system connection to the 4 and 8 ohm speaker jacks is switched through the 16 ohm jack. When nothing is inserted in the 16ohm jack, the ground connection to the other jacks is made. The big problem with this is that the switched jack connection, with time, will always get dirty, end up not closing properly and in some case, just outright fail."


http://www.marshallheads.com/viewtopic.php?f=8&t=48

This. when I first bought a DSL, it had the exact same issue you're describing, and after I did the speaker jack mod just for general purposes, the issue went away. I've since cured the same symptoms you describe by performing this mod on about a dozen other DSL100's.

The issue here is that the sleeve connection on the 4/8 ohm jack gets its chassis ground reference by way of the 16 ohm jack's switching sleeve contact. If the 16 ohm sleeve switch connection gets dirty, or for whatever reason loses proper contact, the 4/8 ohm jacks no longer have a ground connection, and this causes your output issue. It can also cause other symptoms, but yours seems to be the most common. The mod basically entails hard soldering a strip of bus wire across all sleeve terminals to ensure chassis ground connection for all jacks at all times.

Hope this helps.

Hello I am facing same problem. What is the ideal solution for it? I am heading nowhere

 

[mojavemarshall72]

Thanks for the help! Sounds like this speaker jack mod will do the trick. This will be a load off my mind. Don't need my amp going out in the middle of a gig, lol!

 

[japetus]

Sounds like this speaker jack mod will do the trick. This will be a load off my mind.

No pun intended.

 

[IndyWS6]

Thanks for the help! Sounds like this speaker jack mod will do the trick. This will be a load off my mind. Don't need my amp going out in the middle of a gig, lol!

You should consider taking a backup in case that doesn't solve your problem...

 

[mojavemarshall72]

Thanks for tip! Amp fixed and 100%!
Easy fix too thanks to a friend of mine on here. You were dead on with the problem!