2203 blowing mains fuse and it's not the tubes.

Discussion in 'The Workbench' started by Rick Lee, Feb 2, 2020.

  1. Rick Lee

    Rick Lee Active Member

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    Thanks for all the suggestion. I won't be able to dive into it until tonight at the earliest.

    Filter caps are F&Ts and all were replaced when I got the amp about three years ago. Bias caps were done then too. PT and OT are stock original. The amp smelled hot at practice yesterday, but nothing like rotten eggs or anything more than, well, a hot amp. There was certainly no smoke and I can't see any obvious trauma when looking over the board. I have a multimeter and know how to solder. I have a weird job, but if I have a good day out in the field today, I can stay home tomorrow and do paperwork and tinker with this amp.
     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    I suppose it could be OT but I hope not dude.
     
  3. Rick Lee

    Rick Lee Active Member

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    I just handed it off to my tech yesterday. He said it's very likely the PT, but couldn't bench-test it while I was there. I'm just too busy with band and work to deal with it now, and I have plenty of others. Taking my 1969 1959 clone to band practice tomorrow and will use it or my 1987xl for Saturday's gig. My Boss Katana 100w head will be my backup.
     
  4. Rick Lee

    Rick Lee Active Member

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    And it's the worst - PT is blown. Tech says, "HT shorted to ground through filament on one of the sockets."

    Mercury Magnetics wants $500 and 10 weeks to rewind it. Left Chris Merren a vm, but no reply yet. I'll grab a cheapo Hammond or ClassicTone in the interim until I figure out what I want to do.
     
  5. neikeel

    neikeel Well-Known Member

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    Marstran T2562 stand up is 180 dollars plus shipping. That would get my vote.
     
  6. MickeyJ

    MickeyJ Well-Known Member

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    "HT shorted to ground through filament on one of the sockets."

    - maybe he meant through one of the tubes.

    I remember seeing the other day on the schematic no 100ohm resistors going from filament taps to ground ( artificial c.t), instead it had an actual c.t

    you may want to tell your tech to tape up the filament C.T and use 2 100ohm resistors, he'll know what you mean.( like a blackface fender)

    these resistors can ( and do ) blow when trouble is brewing ( plate to heater short ) , they stink and make a noise doing so, a noise you'll hear ( bang! ) and shut your amp off in time, maybe, next time.( also the amp will hum when the resistors blow open)

    its not the worst.
    worst is o/t.
    friend, what you want to do is buy a classictone.
    theyre made in the usa, the original one may have been made in china, I'm not kidding, who knows what work drake/dagnall were farming out back then.
    who has steered you to MM? my god they're not great at making transformers, they're great at marketing.
    both MM and classictone will use the same wire, probably, and as for the laminations, classictone have been making power transformers in USA for I think at least 70 years, the thing isn't going to run too hot.
    Remember, there is no sound difference when using different power transformers as long as current is the same, and voltage(s) is/are the same.
    MM have told people different, and they should be taken to Court for it
    So get this right, MM have told people that ' matched' ot and power transformers bought from them sound better as opposed to buying just the o/t.( lmfao loudly).
    anyway bro, its not a big a deal as you think, labor cost will be maybe 1.5- 2 hours ( i'd do it in no longer than an hour), transformer cost is around 90 bucks plus shipping.
    classictone have been making transformers I believe since the fifties for USA amps , lots of brands, I think their other name is chicago transformers, made a lot of classic fender etc. They're used in Mesa amps.
     
  7. MickeyJ

    MickeyJ Well-Known Member

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    I believe jcm800 output transformers, only some of them, were in fact made in China. This is the only thing that can explain why some of them sound absolutely awful and tinny ( no matter what you do to them) , and some sound so righteous, untouched.
     
  8. MickeyJ

    MickeyJ Well-Known Member

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    you could fix it in no longer than 3-4 hours yourself, you would have to solder I think 8 solder joints.
    the work involves removing knobs, unbolting pots, input jacks and some small nuts that hold the component board onto the chassis.
    the wiring instructions are super easy to follow, we would help you here.
    this is of course only if you feel safe doing so.

    the hardest part of the job is not melting the component board as you remove wires from it and install new ones in the little holes, it's just soft plastic.
     
  9. MickeyJ

    MickeyJ Well-Known Member

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    worried about looks?
    dude just bolt your bell end covers on to the new transformer.
     
  10. MickeyJ

    MickeyJ Well-Known Member

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    plate to heater short means theres a tube thats gone bye bye, and maybe a carboned up tube socket that will need to be changed.
     
  11. MickeyJ

    MickeyJ Well-Known Member

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    bro, I just realized you may need a new tech.

    this guy it looks like, thinks the short is external to the tube.
    what this means is that he's going to use your old tube, and maybe even socket.

    if he uses your old tube, your new p/t will blow immediately.
     
  12. thetragichero

    thetragichero Well-Known Member

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    normal classic tone jcm800 power transformer: http://www.classictone.net/40-18024.html
    upgrade jcm800 power transformer (supposed to run cooler which is always a good thing): http://www.classictone.net/40-18053.html

    haven't used either of these personally but I've used their fender transformers
    if a socket did in fact arc, you'd definitely want to replace it. carbon is conductive. i prefer micalex tube sockets myself. no use saving pennies for an interior product
     
  13. Rick Lee

    Rick Lee Active Member

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    We've only discussed it via text message. I'll go over there today and find out what happened. I've been very happy with my ClassicTones, so I'm fine with going that route for this one, and will figure out what to do with the original PT later on.

    I'm probably grabbing a cheapo DSL100H or HR in the next few days and will do an OT and choke upgrade on it. So I'll just order everything from AmpPartsDirect at once and combine shipping then.
     
  14. Rick Lee

    Rick Lee Active Member

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    One more question - is there any chance my Marshall Power Brake could have caused any of this? I was running it when the problem arose.

    And I was running it last night at band practice with my '69 1959 clone build. That one has Merren iron, but the mesh vent on the top of the head was almost too hot to touch.
     
  15. Rick Lee

    Rick Lee Active Member

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    My tech has a used, but working '72 1959 PT on his shelf. It belongs to another customer, who had a project that never got off the ground. That customer wants to know how much I'd pay for it and if he can have my blown PT to rewind when he gets the project going again. I'm leaning toward just getting a ClassicTone PT and keeping my blown one to deal with later. But how much would a '72 100w PT be worth? I don't see any for sale on eBay or Reverb.
     
  16. thetragichero

    thetragichero Well-Known Member

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    personally i would offer what a new one from classic tone would cost and not a penny more (possibly slightly less but I'm also a deal maker lol). there's some peace of mind that comes with brand new components that "vintage mojo" can't provide
     
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  17. Matt_Krush

    Matt_Krush Well-Known Member

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    Just put a new classic tone (or whoever) and go back to playing.

    Rewind if you're nostalgic, but a power transformer won't change you amps voice...unless the old one was completely out of spec.
     
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  18. matttornado

    matttornado Well-Known Member

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    I would get a ClassicTone and call it a day. I put a Classic tone PT in my 74 super lead and it its fine. No need to spend a shit load on a rewind IMO.

    I think it was around 80 -100 bucks I think. Wasn't hard to replace either, pretty easy actually.
     
  19. matttornado

    matttornado Well-Known Member

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    I been using a Powerbreak for over 25 years and not once has it caused any issues with my amp that I'm aware of. The amp thinks it a speaker cab.
     
  20. MickeyJ

    MickeyJ Well-Known Member

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    powerbrake cause plate to heater short ?
    Nope. it might be suspicious if you burnt out your o/t or blew output tubes.
    just keep your old p/t. its not like its the size of a car wheel or anything, just throw it in some box and forget about it.
    i predict if you do so, after 20 years of playing on your classictone xformer, you'll find it one day and not know where it came from.

    if you have any doubts about the attack on MM i made earlier, send them the message i wrote to you, and see what they say.

    500 fucking dollars to re-wind a jcm power transformer?

    this is the stealing element of that quote.-

    xformer winding places charge big bucks to unwind an output transformer and carefully count turns/interleaving, and if they were the best company in the world, they would take note of the scatter, or winding pattern.
    Get these things right, and use the same wire, and the transformer will sound the same.

    but for a power transformer it's just not like that.
    power transformer patterns are all the same, within a voltage/ current group.
    What they're trying to tell you is that they take two days to unwind and note the patterns/wiring scheme, bullshit. They rip the wire off, literally, and use an old well used pre-set program on their machine. it would take them one hour maximum in total. ( my hunch is that o/t rewinds are mostly done on pre-set programs, from the other output transformers of the same brand/type that they've done.)
    That company is the worst, one day they'll be in Court.
     
    Last edited: Feb 7, 2020

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