Nad...blue Marshall 6100...but It Doesn't Work. Suggestions Please?

Discussion in 'Marshall Amps' started by islandjimmy, Jan 11, 2019.

  1. islandjimmy

    islandjimmy Member

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    I tried this with a known working 12ax7 but it didn't fix the problem. Next, I will replace each of the other ECC83Ms and see what happens.
     
  2. islandjimmy

    islandjimmy Member

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    Hey all,
    I have tried all your tips and so far nothing has worked, but I have a question. Will it hurt anything to just leave it on for an hour or two? Reason I ask this is, when I went to Guitar Center to try a different Marshall 6100, the same exact thing happened to the amp I was testing. The sales guy brought it out to the main room, plugged it in to a Marshall cab and we got nothing. I sat there with a Les Paul plugged into it and talked to the sales guy for about 20 minutes and then all of a sudden I brushed the guitar strings and there was sound. I played the amp for about 30 minutes, loving every minute of it. It sounded great and sold me on the amp. The one at Guitar Center was priced too high and I thought there was something wrong with it so I decided to look elsewhere. It got me thinking about leaving mine on to see if it too decides to wake up.
     
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  3. DPTONE5

    DPTONE5 Well-Known Member

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    I am very sorry to hear about your new amp. I recently sold a perfect condition and working 1994 6100. Never had this problem. The only time I didn't get any sound was when I blew a fuse when a power tube failed. Got a set of matching tubes, biased the amp, replaced the HT fuse and it worked perfectly.

    Do you know a really good amp tech in your area? Where I live, there is a tech at a local repair shop that knows all about Marshalls, including the 6100. It is definitely a different animal because there is so much going on in there.

    Hope you get it working soon.
     
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  4. Marshallhead

    Marshallhead Well-Known Member

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    One little detail in the original post - unlikely to have caused the amp to be DOA, but needs addressed...

    You mentioned you’re using the 4/16 ohm output into a 4 ohm cab - however on your amp head, that output is for a 16 ohm load - your amp doesn’t have 4 ohm compatibility as standard.

    Manual link below. One of the dumber moves by Marshall to label the speaker output on the JCM900 and 6100 models in this way.

    https://medias.audiofanzine.com/files/marshall-6100-30th-anniversary-user-manuel-479802.pdf
     
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  5. islandjimmy

    islandjimmy Member

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    I did not realize that isn't a 4 ohm tap on the back. You're right, it does say 4 ohm on the output jack. That being said, I have swapped that cabinet out for an 8 ohm Fender Cabinet and unfortunately I am still not getting any sound from the guitar. I have used 3 different guitar cables and of course checked the volume knobs on my guitar. It's a real bummer. I can't figure it out. There is a hum from the speaker cabinet which tells me it is getting something from the amp.
     
    Last edited: Jan 12, 2019
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  6. Gene Ballzz

    Gene Ballzz Well-Known Member

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    That sure does look like a jack washer! While I don't intimately know this amp model and/or every jack style in it, but I've certainly seen some styes of jacks that if the nut came off, the jack could fall in far enough for that insulating washer to fall off and if whoever put the jack and nut back in place missed the washer, that jack could be shorting out and causing exactly the symptoms you have described! Probably not likely, but I've seen dumber things happen! also a possibility that if certain jacks got reattached without it's washer, they could get stressed and pulled away from their circuit board mounting. A removal of the chassis from the cabinet is in order, aong with some close inspection of jacks and multi-connectors. Some good, high resolution pics of any suspected problem spots and maybe even a full gut shot would also help us help you.

    Additionally, the fact that there is at least a little bit of hum at the speakers is fairly promising! My guess is that the solution will end up being fairly simple, in the long run!

    Just My $.02 & Likely Worth Even Less!
    Gene
     
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  7. Marshallhead

    Marshallhead Well-Known Member

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    Check all the fuses are ok and also plug a guitar cable into the effects return to see if that gets any sound.
     
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  8. Gunner64

    Gunner64 Well-Known Member

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    The effects return was already suggested and he tried it with no success.

    So are you absolutely 100% sure that the h.t. fuse is good? As in tested with a meter? Fuses can sometimes look o.k. but still actually be bad..are either of the valve fail l.e.d.s lit?

    And as Gene suggested scope out the jacks for anything broken on the inside of the amp. That's kind of odd that a jack washer is just floating around in there. Maybe a nut fell off at some point and the jack somehow got pushed back in.

    I don't know dude..if it's not these simple things you have 2 choices, Take it to a GOOD tech, these amps are fairly complicated, or return it and search for another.
     
    Last edited: Jan 12, 2019
  9. Sixs

    Sixs Member

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    I blew V1 tube the other day , and the 6100 was dead quiet. But it looks like you have tried known working tubes.
     
  10. johan.b

    johan.b Well-Known Member

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    Isn't there an output mute switch on the back of those, for silent recording?....
     
  11. marshallmellowed

    marshallmellowed Well-Known Member

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    Short of taking it to a tech or returning it, there are a couple of things you could try that would help isolate the problem. First off, you would need a 2nd amp and cab (or a combo amp), preferably one with an FX loop. You would run an instrument cable from the 6100 FX "Send" to the 2nd amps FX "Return". If you get sound from the 2nd amp while playing through the 6100, your 6100 preamp is functioning. Next, move the same cable to the 6100 FX "Return" and to the 2nd amp's FX "Send" (similar to plugging a guitar into the "Return", but with a stronger signal). If you get sound from the 6100, while playing through the 2nd amp, the 6100 power amp is functioning. Just a couple of things to try and narrow it down.
     
    Last edited: Jan 12, 2019
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  12. BftGibson

    BftGibson Well-Known Member

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    Rear 6100c.jpg of mine
     
  13. johan.b

    johan.b Well-Known Member

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    Screenshot_20190112-175139_Samsung Internet.jpg
    I haven't looked at one of these in years and I can't read the text in the photo, but isn't that a mute?
     
  14. Jethro Rocker

    Jethro Rocker Well-Known Member

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    Yes it is. I think OP said he tried all these plus has the manual.
    I'm thinking too just cause the tubes light up doesn't mean they work. Might have to try 4 power tubes. Sort of hate to but...
    What's weird is that there is that bit of hum. Maybe the 2 amp method at this point is your cheapest test right now.
     
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  15. Gunner64

    Gunner64 Well-Known Member

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    Now if a power tube goes doesn't the corresponding valve failure led light up on this model? It would on my 2100 sl-×.
     
  16. anitoli

    anitoli Well-Known Member

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  17. anitoli

    anitoli Well-Known Member

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    If it has an over current condition it does.
     
  18. anitoli

    anitoli Well-Known Member

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    I don't know why anybody would ship an amp if it wasn't working but that washer leads me to believe that one of the boards has been removed. I need to see how the ribbon cables are routed, if they are incorrect you wont get any sound.
     
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  19. Gunner64

    Gunner64 Well-Known Member

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    The 6100 man's back... I'll shut up now..:D
     
    Last edited: Jan 12, 2019
  20. islandjimmy

    islandjimmy Member

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    Yes, mine has that too and I have switched it on and off many times during this process, but still no luck getting sound from the guitar. I think we're close though. The speaker cabinet hums and everything looks right but there is zero sound from a plugged in guitar. I left it on for an hour last night but nothing changed. I also reset all the tubes and replaced various 12ax7s but still nothing. I'll keep searching! I know the answer is right around the corner. :)
     
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