Can someone answer a couple amp questions?

Discussion in 'Amp Tech Center' started by dickey, Aug 31, 2020.

  1. dickey

    dickey Friend of Leo's

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    What does it mean when someone refers to modding a vintage amp when they say "Remove the death cap". What exactly is a "death cap"?

    What does it mean when referring to your own build when they say "5f1", 5f6, etc? I've only bought amps & guitars; never built one.
     
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  2. rjtwangs

    rjtwangs Tele-Afflicted Silver Supporter

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    I'll let someone else answer the question re; the death cap. The 5f1 is the model number for a narrow panel tweed Champ. The 5f6 A, is the model number for a tweed bassman. Hope this helps a bit!


    RJ
     
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  3. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    the death cap is a capacitor on the AC input of the amp to chassis. There's lots of mixed data on if it could actually cause death, but you can google it for a good time. In theory, if the cap fails short (as opposed to failing open) it will let AC go straight to the chassis, posing a shock risk. There are modern appropriate caps that can fail in a safe way, but when we service a vintage amp we remove that, disable the ground switch, and add a three-prong grounded cord.
     
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  4. stantheman

    stantheman Doctor of Teleocity

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    Wally is The Man, hopefully he’ll see this.
     
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  5. AJBaker

    AJBaker Friend of Leo's

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    The death cap is something from the good old days before three pronged plugs, and that isn't considered safe by today's standards.

    The model numbers in that format are pretty much for 50s fender amps.

    For example, there were a number of models called the 'Deluxe', but these models would change over the years. The specific model name would be written on the tube chart stuck to the inside. I believe the first one was called the 5a3, and the most famous one, made at the end of that decade, was the 5e3 (which we now call the 'Tweed Deluxe').

    If you browse a website where they sell the kits you'll get an idea for what is what.
     
  6. dogmeat

    dogmeat Tele-Afflicted

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    you mean '70's amps. yep, in the old days the cords and receptacles were 2 prong and you could insert the cord either way. the 2 power wires connected to the transformer only, and not to the chassis or anything else. but the chassis could pick up extraneous noise from the transformer and other things, so the the cap was put in to help filter that out. it was on a switch to change polarity. and getting it wrong made for voltage differentials between different amps. if you and another player were out of phase you could get a mild shock by touching. and a bad cap could actually make the chassis hot. your guitar too. or the microphone... even today I still slap the mic with the back of my hand out of habit. somewhere in the early late 60s, early 70s they made a rule to have 3 prong plugs with a standard polarity layout. if your amp still has that old system its best to remove it and put in a modern 3 wire setup. I doubt it can kill you but I got the bejabbers shocked out of me on a wet stage once
     
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  7. Jon Snell

    Jon Snell Tele-Holic

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    The actual purpose of the 'death cap' was to present a virtual ground to the chassis, switchable from one pole to the other, hopefully reducing mains hum.
    We use a three pin plug with a safety earth/ground nowadays.
    Class X and Class Y capacitors fail in a controlled way and are used in mains interference filters. The standard PET capacitor may be rated at, for instance 1000volts, still fail by going short circuit or at best leak.
    Yes, back in the day, touching the ground wire would either increase or decrease the hum, depending on which pole the death cap was switched to.
     
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  8. schmee

    schmee Doctor of Teleocity Silver Supporter

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    it's just the designation by Fender of what the amp design or circuitry it is. After the tweed style amps Fender went to a date based designation. Like AB763... means it was final designed in July (7) of 1963 (63)
    There's good reference info on these amps here; http://www.thevintagesound.com/ffg/
     
  9. dickey

    dickey Friend of Leo's

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    Thanks for all the answers, guys. I learned something new here.
     
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