Help with Marshall dsl

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by azimuth, Dec 21, 2009.

  1. azimuth

    azimuth Member

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    Hey,

    I bought a Marshall dsl from eBay and it worked well for about five minutes, then a small amount of crackling (as per a sketchy cable) and then nothing- in fact, the light on the power switch went out even though it was still in the up position.

    Could this just be a fuse or could there be serious issues lurking? If I can just send it back and walk away should I?
     
  2. phsyconoodler

    phsyconoodler Member

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    If the light went out it definitely blew a fuse.Replace the fuse and try again.Make sure the speaker impedance is right for the output jack you have it plugged into.
    If it blow a fuse again it may have a bad power tube.Tubes are the first thing to suspect.Get used to replacing tubes in a tube amp.Don't blame it on the amp or the gut who sold it to you.You also need to make sure it's biased correctly.Too hot a bias setting will draw too much current and can blow a fuse.
    It has two fuses.One main fuse and one HT fuse.
     
  3. kennyramjam

    kennyramjam Member

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    Also make sure that you use the right value of fuse. Sometimes there is a tendency
    to increase the value of the original fuse to see if the problem will go away with a bigger
    fuse. BAD idea. The fuse is for protection of other componenets after the fuse. Installing
    a larger fuse to assist in diagnosis may damage the amp in addition to the problem already
    present.
     
    Last edited: Dec 23, 2009
  4. SatelliteAmps

    SatelliteAmps Member

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    If a tube was bad, it should blow the HT fuse, not the main power fuse (which this did as it turned off the power light). These amps do have a few major issues with how they were made. Mostly due to cold solder joints that occur during the manufacturing process, as well as a rectification overheating issue.

    Putting another fuse in to test this out is a BAD idea if you have no idea what you are doing inside the amp. The reason this is bad is that the rectification issue has caused extremely burned circuit boards, usually by people repeatedly trying to replace a fuse to make the amp work. Take it to a tech and let them check it out for you. If you are comfortable working inside of amplifiers, then pull all the tubes first, pop open the chassis and start looking for burn marks before firing it up again. If you can't find any, make sure to use a variac and an amp meter to watch everything when you do fire it up.

    Most tube amps don't need to have tubes replaced that often if they are running correctly, and being used somewhat regularly. Players that tour heavily should have their tubes replaced about once a year, but most normal people can go 2-5 years with no problems.
     
  5. azimuth

    azimuth Member

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    Thanks guys.

    I don't know what I'm doing at all so i'm bringing it to a tech.

    Another thing was the reverb wasn't working at all, even full. It was up all the way when the amp crapped out. Did that have something to do with it?
     
  6. JerryP

    JerryP Member

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    If you had another set of power tubes and a new fuse (correct value) it would be worth a try to pop them in. It's very common to see power tubes damaged in shipping as well as reverb tanks. There are many things that can cause these problems, but a shorted power tube and a damaged reverb tank would be my first guess. I've seen it many times. The HT fuse is usually the one to blow with a power tube problem, but the mains fuse can blow too.
    Jerry
     
  7. VanR

    VanR Senior Member

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    Take it to a tech. If it was me I would replace the fuse with a new one, pull all the tubes and turn it on and see if the fuse holds. If so most likely a bad tube. Then I would turn it off and insert all the preamp tubes and turn it back on. If it holds turn it off and insert power tubes. See what happens then when you turn it back on. Sometimes you have a bad fuse. It does happen, but not likely. I going with a bad power tube myself.
     
  8. azimuth

    azimuth Member

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    Took it in.

    Amp died because seller used the wrong fuse in the mains. Me cranking the amp popped the fuse. That was it.

    One dying preamp tube was replaced too. The reverb doesn't work at all, that appears to be a seperate issue that I'm not going to worry about for now (I have
    a line 6 m9 for the fx loop).

    I'm glad I took it in, as I'm sure I just would have replaced the burnt fuse with the same wrong type. Thanks for all the help.

    If you're in NJ I highly recommend Toobz in freehold. Really really excellent service.
     
  9. JerryP

    JerryP Member

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    Sounds fishy to me. He would have had to had a very small fuse in there. Another thought is that if the original owner had to change the fuse then he had something blow that fuse. My gut feeling tells me be prepared for another blown fuse and if that happens put some power tubes in the amp.

    Pull the reverb tank out and inspect the wires inside. Sometimes the small wires will get ripped of from being bounced around in shipping. I've had many amps (several DSL's) that had reverb tanks damaged in shipping. Should be an easy fix.
    Jerry
     
  10. phsyconoodler

    phsyconoodler Member

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    I've had a few DSL's come in with no reverb and found that the cables were switched around because someone had had the chassis out and reversed the cables.
    Swap the cables and see if it works again.
    Sometimes guys replace the fuses with fast-blow ones and they blow easily.They need to be slow-blow in that amp.
     
  11. kennyramjam

    kennyramjam Member

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    If you haven't thrown away the original blown fuse, it's easy to see if it was too
    small. Just look at it and see how it compares to what's written on the amp. If,
    indeed, the only problem was too small of fuse, you are indeed very lucky. It's
    not often a problem is that simple, but it can happen. I was having problems
    with too low of plate voltage in my Marshall, and it turned out to be a corroded
    mains selector. Sometimes, problems are simple. Good luck.
     
  12. azimuth

    azimuth Member

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    Ok, well, here's the next part in the saga.

    Got the amp home, tried my cab. I'm noticing that during the first few minutes of play (not straight away) the amp will make a scratchy staticy sound. This is faint and does not cut out the gtr signal. It sounds exactly like someone working a scratchy pot back and forth. So far I've only played the amp longer than 20 minutes once, that time it made the noise for a couple minutes and then stopped. I really hope this is a warming up thing, but I've had like 5 other tube amps and never noticed this. It didn't do it in the shop, but it's not a buzz like line interference. It really sounds like a messed up cable. Again, it's low. It's not noticable until you stop playing. It's not affected by knob settings or any input- does it with volume all the way down. I have yet to have time for several marathon sessions to see if it's just a startup issue, but I'm wondering if this sounds familiar. All tubes were tested yesterday and came up good except for the one that was changed.

    Also this is a weird one, but when playing the green channel the gain knob of the red channel affects the tone. This is something I've never seen and makes me really curious.
     
  13. azimuth

    azimuth Member

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    Fuse was a 2amp vs the required 4 amp if my memory serves.
     
  14. azimuth

    azimuth Member

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    Wait a sec,

    if there's a loose connection inside the reverb tank that would / could cause no verb and post preamp random scratchy noises, right?

    Should I just pull the rcas to the reverb tank? Is that in any way unsafe?

    Sorry for my internal ranting monologue.
     
  15. SatelliteAmps

    SatelliteAmps Member

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    You can pull the wires, shouldn't hurt anything.
     
  16. phsyconoodler

    phsyconoodler Member

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    An opamp driven reverb is ok to disconnect.Did you try swapping the reverb cables?
    Also,did you have the output jacks cleaned and checked?
     

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