Marshall jcm 2000 DSL sound cuts out!

[J.denots]

I had a fuse blow a month ago and I had to replace the power tubes to get it not to blow. I biased it and it worked great for a month, but now the sound totally cuts out for a minute or so and then comes back, keeps doing this. I have never replaced the pre-amp tube that is covered with the metal and the spring. Is this tube a different type than the other 12x7s? Could this be a factor?

[izzybell2810]

I had a fuse blow a month ago and I had to replace the power tubes to get it not to blow. I biased it and it worked great for a month, but now the sound totally cuts out for a minute or so and then comes back, keeps doing this. I have never replaced the pre-amp tube that is covered with the metal and the spring. Is this tube a different type than the other 12x7s? Could this be a factor?

The tube with the shield is the first pre amp tube and it's there to shield the tube from RF. Knowing the DSL amps I would say that something is loose inside the amp. When it cuts out give it a whack with a rubber mallet or something doeas the sound come back? If so there's a loose connection or a bad solder joint. you could also try a patch lead from the effects loop send into the return.

[J.denots]

Marshall still dont work.

Tried tapping, nothing. I have a signal coming out of my effects send into my rack unit, i can tune through it. Do you mean plug a guitar into the effects return?

[izzybell2810]

Tried tapping, nothing. I have a signal coming out of my effects send into my rack unit, i can tune through it. Do you mean plug a guitar into the effects return?

No, I mean take a lead plug one end into the effects send and the other end into the effects return with the guitar or some other signal plugged into the input.

[J.denots]

DSL 2000 Mystery

Thank you for the input! I tried plugging a lead into the effect send and return and the amp started working! Even when i pulled the cable out it kept working. I had not heard a peep out of it all day trying different things. Is this different than running the effect send through my rack and back? I still need to figure out whats causing this. Please help. Jer

[izzybell2810]

Thank you for the input! I tried plugging a lead into the effect send and return and the amp started working! Even when i pulled the cable out it kept working. I had not heard a peep out of it all day trying different things. Is this different than running the effect send through my rack and back? I still need to figure out whats causing this. Please help. Jer

Hi, your signal travels through the contacts of the effects loop, when you insert the jack it breaks that contact and the signal travels to your rack, pedals or what every you have conected and then back to the amp. If you push a plug into the loop with the chasis removed you will see what I mean. Those contacts were obviously dirty. Give them a clean!

Dave.

[J.denots]

Thanks, i will try that after work

I'll let you know if it fixes things

[J.denots]

send and return contacts?

It does seem to come back on if I plug into the effects loops, also seems like there could have been crud in the tone shift button, it was crackely. Do i clean the send and return contacts with electro-wash? Can i spray electrowash everywhere, or only in specified areas? I took the amp apart and now i need to know what to do to clean the parts. I wiped dust off of parts and blew some air in it. What else can i do?

[izzybell2810]

It does seem to come back on if I plug into the effects loops, also seems like there could have been crud in the tone shift button, it was crackely. Do i clean the send and return contacts with electro-wash? Can i spray electrowash everywhere, or only in specified areas? I took the amp apart and now i need to know what to do to clean the parts. I wiped dust off of parts and blew some air in it. What else can i do?

Hi again,
If you insert a plug into the send and return you will see the contacts of the socket lift. Give them a spray (between the contacts) I also clean the contacts with a very fine abrasive, I use a cut down emery nail board stolen from my wife, but a small sliver of 1200 wet or dry paper will do. You may as well give the mechanical parts such as pots a clean while you're in there.

Dave.

[J.denots]

send return jacks are closed

There is just 2 totally closed boxes for the send and returns. I cant see anything move when I plug in. I cleaned them up but it still cuts out....
I will try the fine grit paper from the outside. Thank you, Jer

[izzybell2810]

There is just 2 totally closed boxes for the send and returns. I cant see anything move when I plug in. I cleaned them up but it still cuts out....
I will try the fine grit paper from the outside. Thank you, Jer

Ahh, I was presuming your amp had the open type sockets. You could try spraying them with switch cleaner using the straw to get right inside. If that doesn't work I'm not sure if you can get into them and you may have to replace them, or get them replaced.

Dave.

[J.denots]

Still cuts out!!!

The send return jacks don't seem to make a difference anymore. When i first turn it on, sometimes there's no sound and i can only get it to work by strumming my guitar really hard. Once it comes to, it seems to work fine- for a while. This makes it seem like maybe its the input section. The amp works 90% of the time, and sounds great. I just cant count on it at a gig. There is nobody around here that can do the repairs, and i'm afraid if i send it off somewhere it will get damaged during shipping. I don't know what to do. I'm Thinking about buying a mesa. Thanks again for your time and help!
Jer

[52 Bill]

The send return jacks don't seem to make a difference anymore. When i first turn it on, sometimes there's no sound and i can only get it to work by strumming my guitar really hard. Once it comes to, it seems to work fine- for a while. This makes it seem like maybe its the input section.

Do you still have a jumper cable in the break jacks? Does hitting the amp still fix or cause the problem?

[J.denots]

Thanks for your help. I am running a send and return to my rack unit tuner and eq. I have tried unplugging them when it cuts out - nothing. Banging on the amp doesn't seem to do a thing.
Jer

[52 Bill]

Banging on the amp doesn't seem to do a thing.

That series of amps has a very commom problem regarding the dc power supply for the pre-amp tube filaments.

When the amp cuts out does the signal sort of fade out?

If it does, look at the center of the first pre-amp tube (12ax7). You should see the orange glow of the tube filament in the center of the tube structure. If it doesn't light up then this may be your problem.