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    Ever been electroshocked by your JCM2000

    Did anyone measure a residual voltage on the filter caps in a JCM2000 DSL100? I never did. Found this thread about bleeding the filter caps: DSL100 | Bleeding Filter Caps I measured for voltages on R71, as said in the article, but no residual voltage at all. My guess is that R73 and...
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    One dead tube = silence?

    Thanks for the reply. The problem is not in the fuses I measured them. Yeah, a bad soldering or the fuse socket could be it. I have soldering skills, but I doubt it is possible to measure voltages while the amp is on ... this is quite tricky and traces may be very hard to reach. Anyway...
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    One dead tube = silence?

    Well, after a couple of months the problem is back. Today the amp made no sound at all, and I saw the first tube was dead again. The other three happy and glowing. I took off the back cover, took the dead tube out (the first power tube from left, next to the pre amp tubes), took out the...
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    One dead tube = silence?

    Guys strange thing is, I took the amp home, checked all fuses HT, main, then opened the amp and checked all fuses inside. All fine. Put the amp back together and guess what: all is fine. I'm using the amp for 2 weeks now and still no problems. I guess a loose contact or so ... :hmm:
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    One dead tube = silence?

    Ok, thanks! Will check and replace the HT fuse. Replacing only the dead tube will result in a non-matched tube amp ... if this is a good idea or not will be a whole other forum thread, I suppose ;-) (I will bias them, though)
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    One dead tube = silence?

    No, because the other tubes are glowing I thought the fuses should be ok ... However, this may be a bad assumption. Where is the HT fuse located?
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    One dead tube = silence?

    I have a DSL100, and today I got no sound from the amp. So I opened up the back side, and found out that one power tube is not glowing. It's the first power tube from the left. (looking in the amp from the back-side, on the left are the pre-amp tubes and on the right the 4 power tubes)...
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    There might be another cause for the popping: no diode across the relays. I think I will insert diodes across the coils of relay 2 and 3 to cut out high voltage clips when switching.
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    That seems to be a relais. I also see a diode across it; that's also an indication. (the diode short cuts peak voltages when the relais is switched). I'm not sure about optocouplers versus relais; I guess it's different versions of the amplifier. About the switching sounds ... a bit of a...
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    So the LDR seems to be fine? Then something else is wrong. What would be the next step? I read about "replacing front caps" ... what does that mean?
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    I order to solve the switching channels noise (pops) problem I did the optocoupler check as indicated in this thread. green channel: 1411 ohm red channel: 1.5 MOhm, and this value increased to 2.4 MOhm during 1 minute or so. What does this say? I am not sure it I measured the right component...
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    Thanks man for your help! Will try this too.
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    Marshall DSL 50/100 Clean/Crunch Footswitch - at last!

    I installed the mod too, option 3 and added the volume knob on the front of the amp. Neat! :lol: It all works great (tested only at low volumes), but there seems to be one strange thing: I get a 'pop' sound (in the speaker) when switching from green to red channel back an forth.:( It seems...
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    DSL100 5 dead tubes

    I think he was referring to the power-divider which indeed is R67/R73 in the schema. If you take out the EL34tubes, and measure from pin 2 or pin7 to ground, you should find 50 ohms.
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    DSL100 5 dead tubes

    Good news! The F1 fuse was the problem after all. The fuse itself was ok, ... however its socket had a bad soldering. I re-soldered it and now all tubes are glowing happily. Thanks for the input guys! :wave:
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    DSL100 5 dead tubes

    PS I'm looking into this thread now: they say check solderings etc. Another DSL Marshall problem.. Think that will be my next step.
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    DSL100 5 dead tubes

    sorry guys, I wasn't clear on this. Yes, I checked the fuses with a meter. All good. PS I have a degree (engineer) in electronics, but I have not much experience in repairing a DSL100. But thanks for your warnings anyway. It is always good to be carefull with tube amps!
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    DSL100 5 dead tubes

    Ok I finally got 5 minutes to open up the amp ... to my surprise all fuses are ok :confused: There are no burned areas as far as I could see ... so I'm a bit confused (funny: con-fused :-) ) Anyone a bright idea for me to check?:hmm:
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    DSL100 5 dead tubes

    The fuse looked ok ... I will test it of course, but what would be the next check if it is not the HT-fuse?
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    DSL100 5 dead tubes

    Today I switched on my JCM2000 DSL100 but no sound!:( Looking inside (removed back cover) I found that all preamp tubes were dead (not glowing) plus V1 of the power tubes. So tubes 1-5 are dead, 6 7 and 8 are glowing. :confused: Anyone ideas? The power tubes were recently replaced, the...

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