DSL 50 no sound...help

[doostain]

I looked around on here but didnt find the right scenario that I have.

So I bought this amp off ebay from a guy who never played it. I got it and it was brand spankin new. Not one scratch! It was from 1995 or 98...with the original tubes. I jammed on it and gigged with it for a year and then one day, during practice, the signal just dropped. I shut it off for a few and booted it back up and it was fine. Then 20 minutes into a gig it took a shit and wouldnt work. Packed it up, went home and then it worked for 45 minutes, then crapped out. I tried it again a week later, worked for 10 minutes, then nothing. Now it does nothing. Tubes dont glow, they didnt glow when it crapped out either. When I turn it on, the front button lights are on but no sound. It also makes a slight hum...like a quiet tattoo gun. I bought new tubes and they are on their way....am I going to have to take this in to get fixed?? Is this a common problem for Marshalls? Will new tubes fix the problem. Speaker cables arent shorted, running it at 8 ohms, never used the effects loop, never cranked it past 6...(even though it goes to 11)...need help, my baby is sick! Thanks to the tube heads who help!! - Doo

[Mark Black]

Couple things to try:

Plug a guitar cord from the effects out jack right back to the effects return jack - if it starts working that probably means the switching contacts in the effects return jack are dirty or oxidized. Possibly just running a plug in & out of the effects return jack might make them start working again if that is the case.

If that doesn't work, try plugging your speaker cab into the 16 ohm output. You don't want to get too carried away with cranking things into the impedance mis-match, but if you get sound that probably means a similar set of switching contacts in the 16 ohm jack are dirty or oxidized (or burned up - known to happen on these amps). If this turns out to work the amp might need to be serviced by a tech since the jack burn-up is so common - jack would need to be replaced at minimum and probably should have the switching contacts bypassed to prevent future problems.

In any case don't wank on it much while getting no sound output - you could be harming the output transformer.

Edit: Oops - I just noticed you say the tubes aren't glowing. If you mean no orange heater glow that probably would point to internal problems best serviced by a tech...

[Enzo]

And the next question is this. Are ALL the tubes dark, or just some?

[bluesfreak]

This amp has internal fuses for the heaters (F1-F3) so I would recommend to check those.
Also V1/V2 are heated using DC and the Rectifier is known to fail often so this is another point. With the tubes removed you can check if heater voltage is present, measure from pin 4-9 and 5-9 on the preamp tubes and 2-6 on the power amp one's, you should get around 6.3V, remember V1/V2 is DC all others AC...

[Amp Kat]

The amp was telling you that you needed new tubes and when they went they probably went hard as they always do. It either blew a fuse,a screen resistor or opened up the plate resistors or the Cathode current sense resistors. Jerry at FJA Mods also found some interesting things that happen when these tubes short and hopefully it's not that but you may want to check his site out for observation.

[doostain]

Thanks guys!

[doostain]

DSL 50 - Hummin like a bee hive

So I put the new tubes in. Opened it all up and all looks good....no char marks, no blown caps, no loose cables, no blown inline fuses or external. I booted it on and nothing. I turned it off and waited 10 min and retried it, and they started glowing. Gave it a couple to warm up and jammed on it. Clean channel is good, but when on crunch it has a loud hum. I also noticed that when the guitar comes close to the power transformer it gets way louder(the hum). Any ideas on what my problem is? How do I check w/ meter to see if its bad?

Thanks for all info and help.

[bluesfreak]

Singlecoils?

SCNR...

[doostain]

Nope. I got a LTD EC-400 w/ active EMG humbuckers, the cab is a line 6 w/ new celestions in it. 16ohms wired down to 8 per side. I've ran it at 8ohm since I got the head. Im more a quality then quantity guy.

[Enzo]

If you get loud hum when you walk close to the amp, turn the guitar volume to zero. Does that kill the hum? if so, it is your pickups picking up the powr transformer. Not the amp's fault.''Likewise, stand there, and it hums, now don;t back away, just turn 90 degrees and face the side of hte stage. Does aiming the guitar different change the hum? Again if so, it is your pickups sensing the power transformer.

[doostain]

It hums louder by PT then 90, but it still hums. Ill have to try turning the guitar down and checking. Is there a way to fix that besides a noise gate?

Do active pickups find/get more hum from PT than passive?

Please feed my brain...

[bluesfreak]

Does the OD Channel hum also when no Guitar is connected? If yes, there is an issue with either preamp tube heating or B+ supply (filter caps). If it only hums with a guitar connected it could be a ground problem with your cable and/or guitarso I would try a different cable and an different guitar (if available) and check.
Usually Humbuckers should not pickup too much hum at all but there will be some always, especially with active Humbuckers as they have already an internal preamp which will amplify all signal picked up by the coils. However, the principle of the Humbucker should avoid this but this is only possible if both coils are 100% identical otherwise a small amount of hum can be generated if near a RF noise source.

[doostain]

With no guitar plugged in, theres no hum...just slight hum of amp itself. Ill try new cables and another guitar.

When biasing this, if I want more punch set it to maybe it to 40 instead of 45? I got new tubes matching at 31....

[bluesfreak]

Depending on type of tube and B+ a bias of 40mA is possible, 31mA is a bit low for EL34...
BTW: How good are your tubes matched? Mismatched power tubes can also cause hum...

[doostain]

mullard el34 new matched by tubestore.com ...they are pretty good about getting them close. It hummed before I put new tubes in as well.

So those tubes shuold go up to 45 per side then?