Trouble with my DSL40C

Discussion in 'Marshall Amps' started by Mike31533, Aug 2, 2020 at 1:27 PM.

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  1. Mike31533

    Mike31533 New Member

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    My DSL40C has no sound. The only way to get any sound coming from it is plugging into the return jack on the effects loop. What could be wrong?
     
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  2. SkyMonkey

    SkyMonkey Well-Known Member

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    Can you see if any of the preamp tubes are dead (the 4 smaller ones).
    In a darkened room they should all have an orange glow.
     
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  3. SkyMonkey

    SkyMonkey Well-Known Member

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    Oh, and whilst your situation sucks, welcome to the MF anyhow @Mike31533 :welcome:
     
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  4. pedecamp

    pedecamp Well-Known Member

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    Check your fuses, check your tubes. Welcome to the forum. :yesway:
     
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  5. Micky

    Micky Well-Known Member VIP Member

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    Preamp tube, maybe a fuse?
    Is the sound wicked loud thru the FX return?
     
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  6. Micky

    Micky Well-Known Member VIP Member

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    Without more info it is hard to diagnose.
    One thing that can cause this is a preamp tube failure, or a problem with FS3, which is a slo-blo 1A fuse.

    FS3 is in the circuit that supplies the lo-voltage (regulated) to the main board. It also provides DC heater voltage for V1, a method to reduce noise in that preamp tube. I would look there first.

    If you are uncomfortable or unfamiliar with working on the chassis of an amp, then take it to a qualified tech.
     
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  7. scozz

    scozz Well-Known Member

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    Welcome to The Marshall Forum @Mike31533. Lots of guys here with a wealth of information,......but they’ll need more info on what exactly is going on before they can help you out.
     
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  8. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    :welcome: To the forum
    I have not read the entire thread but I can tell you that the problem is a bad preamp tube, if it’s already been addressed just skip my post .
    But take a known good preamp tube and check one at a time till you find the culprit, one of mine did this and this forum is where I read how to find the problem. And I did,
    Cheers to getting your amp back on its feet. They do kick ass.
    Mitch
     
  9. jeffb

    jeffb Well-Known Member

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    90% of the problems with tube amps, are the amp's tubes.

    Try rotating in known good pre-amp valves into V1-V4 until you find the culprit/s


    and fwiw- not all pre-amp tubes show/will glow significantly when running (as mentioned- use dark room)
     
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  10. Mike31533

    Mike31533 New Member

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    The tubes are all glowing.
     
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  11. Mike31533

    Mike31533 New Member

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    No. There is sound but not very loud
     
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  12. Mike31533

    Mike31533 New Member

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    I checked the fuses already. They seem fine.
     
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  13. Micky

    Micky Well-Known Member VIP Member

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    Checking a fuse requires a multimeter.
    Many fuses that 'seemed' fine to me were actually blown when tested.
    Pull them out and check them, especially FS3.

    Also put in your spare set of tubes one at a time
    to see if they are the culprit.
     
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  14. Mike31533

    Mike31533 New Member

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    I'll replace the fuses and see if that works. That's the cheapest thing to do right now. There's no sense in taking it to the shop right now.
     
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  15. CraigerSS

    CraigerSS New Member

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    Try putting a patch cable between the send and return of the F/X loop. This will bypass the loop thus may eliminate f/x loop issues.

    Good Luck and welcome to MF.
     
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  16. South Park

    South Park Well-Known Member

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    Greetings from cal . Put some good tubes in the preamp if no sound send it to the tech . It may have other stuff that need to be looked at
     
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  17. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    Do has Micky has said one at a time you will find the bad tube, when mine omits the same symptoms you are having, all tubes looked the same but one was not letting the sound through, I cannot remember which one it was but I did fix it with this simple test..
    Cheers
    Mitch
     
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  18. Mike31533

    Mike31533 New Member

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    Thanks guys for all of your input. This is the first tube amp I've ever owned. I bought it used from a pawn shop locally for $150. I took a chance that it might be something that would be an easy fix.
     
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  19. scozz

    scozz Well-Known Member

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    I hope it’s a quick fix for you @Mike31533.

    Welcome to The Marshall Forum! :thumb:
     
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  20. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

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    I agree with most above. Try V1 or V4 preamp tube first. Well, all one at a time but my giess would be one o those.
    Oh and must add - I assume you are plugging guitar directly in? No effects, nothjng? Amd that guitar and cord work with another amp?
     
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