Marshall dsl 50 problem!

[Ruepert t justice]

I have a problem with my Marshall dsl 50, NO SOUND. The power switch shows the amp to be on and you can hear that the amp is on. The power tubes do not glow when the amp is on. I checked the standby switch and it was o.k. There is also no glowing preamp tubes. I checked f1 and f2 and both are good. Does anyone have good advice on what to check next or what are likely reasons for the kind of problems i am having.

Here is some background. A while back when the amp was working, i starting to notice that the amp was hissing and popping a bit. The longer it was on the more it hissed and popped. It got to the point where the amp noise was to loud to use for more than 5 or so min. I figured it was just dirty so i used contact cleaner on it and it seemed to help a little. The amp seemed to hiss and pop more often and only when something was plugged in to it and it was on. In standby from what i remember the hiss and pops could not be heard. I bypassed the power amp stage and did not think i could here it in the preamp tubes, so i replaced the two power tubes. The noise was not as bad after that. I do not know if the noise was just the fact that its tube or if the noise is a bit more than the amp should be making. Well, i was trying out a different speaker cab. I used a cable that had a short in it. So, when i turned on the the amp, and took it off standby, I did not have a speaking load on the amp (because of the shorted cable).That was when the amp stopped making sound.

That is when i notice the tubes did glow at all . NON OF THEM.

[Chuck H]

By your description, I think this problem is best taken to an experienced tech. I looked at what I could find for a schem and though it seemed to be as complete as intended, it wasn't clear on some things like the filament supply. For some reason your tube filaments are not heating. On most amps there is no connection between that and running the amp into an open load. The power indicator light is illuminated. On most amps that would mean that you don't have a mains fuse blown, which should kill the filaments but also the indicator light. If there are some kind of regulators on the filament supply, that may be the problem. but the schem I saw didn't show the filament supply. Plus there is the initial problem of the popping and crackling that was not addressed until the amp stopped lighting the tubes. Unless this is caused by some frequent problem with that model, and someone here knows about it, it all seems a little obscure and I think a trip to an amp shop may be your best option.

[Enzo]

Here is the page with the power supply. If all the heaters are dark, then the amp will make no sound. See the power transformer wingind marked "heaters"