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The "Death Cap" Thread...

Discussion in 'Amp Central Station' started by cklingo, Apr 27, 2010.

  1. cklingo

    cklingo Tele-Meister

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    Hi,

    I checked the archives and didn't see a thread with this topic. Perhaps this could be a resource where users go and find out if their vintage amp has the dreaded "death cap".

    Here's my question, I'll add a photo later if it helps....

    I have an amp that I love playing but I sense it may be dangerous. It's a Montgomery Wards 55JDR8436, there isn't a model name or number. The tubes are 6X5GT, 6V6GT, and 6SJ7. It's tan faux tweed, with an orangeie grill and diamonds, kinda like a Vox. 8 inch Rola speaker. The thing honks. I actually bought it from an old timer, the original owner. He bought it with a killer lap steel. I even have the original receipt (somewhere, damn). I couldn't find the amp or a schematic anywhere on the web.

    So, death cap? Or, play it!

    Thanks in advance!
     
  2. Wally

    Wally Telefied Ad Free Member

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    Congrats on finding an amp you like. Now, how do you maintain it, right? Does it still have a two-prong power cable? If so, the best safety measure you can make is to install a grounded (3-way) cord. While doing so, one might want to remove the 'death' cap...and yes, it will be there.
    I also strongly suggest replacing the electrolytics...filters, bias and bypass caps. It is of an age and needs this, imho. IT woudl be a pity to lose a transformer due to a catastrophic cap failure, and the amp will sound even stronger with fresh caps, ime.
     
  3. Billm

    Billm RIP

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    If it has two-wire cord and a ground switch, it has a death cap. Or even without a ground switch, it may have a cap from one side of the AC line to ground. In either case, it should be converted to three-wire and the death cap should be removed.

    I agree about replacing all the electrolytics.
     
  4. cklingo

    cklingo Tele-Meister

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    Thanks. I have a collection of approximately 30 small tube amps...Fender, Gibson, Silvertone, Supro, Harmony, Kalamazoo, Ampeg, etc. I'm not interested in modding to a 3 prong, I'm just interested to know if this specific amp circuit has a higher propensity to zap me. I'm not a tech and don't really care to understand the details of why I could be shocked. I'm just seeking to know if this amp's circuity is the "death cap" type. The variety where people in the know recommend an isolation transformer.

    BTW, can anyone recommend a source for an isolation transformer so I can enjoy these gems in their non-modded state?

    Thanks in advance.
     
  5. Jeff B.

    Jeff B. Tele-Meister

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    Check hammond for a iso transformer.
     
  6. Jaybird

    Jaybird Tele-Meister

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    I may be mistaken, but by the tube lineup, you have a power transformer on your amp. An isolation transformer would be redundant. It would be more efficient and less costly to remove the death cap and install a three prong plug. Save the old parts for posterity if you wish. Replace the old electrolitics also. Sounds like a nice amp.
     
  7. Wally

    Wally Telefied Ad Free Member

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    cklingo, if you are not worried about installing a grounded power cord, then don't worry about the death cap. Play on. Lack of understanding never kept someone from entering into a dangerous situation. Actually, the lack of understanding encourages one to walk into danger without even knowing it. Ahh....bliss...that sweet condition.... (;^)
    Iso tranny. THe only time you are going to need an isolation transformer is if you have an 'American 5' type of amp. These amps carry tubes that consume the amount of voltage that the wall source provides. THe tube numbers will be 50, 35, and 12. Those numbers indicate the voltage used. The heater filaments take up another 6 volts....so that gets you close to 110, which was the usual wall voltage back when these amps were built. Some of these AMerican 5 amps have isolation trannies and some don't.
    Take care. The problem with being 'zapped' is that it will happen before you realize it....and that is much too late to worry about it....or to do something to decrease the possibility of 'ZAP!'.
     
  8. Donnie55

    Donnie55 Tele-Afflicted

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    I have a question...Please correct me if Im wrong ( and I know you will ...lol )
    For the death cap to zap you , wouldnt one side of the connection have to come off and ground to the chassis to pass the current thru ? And what are the chances of that ?
     
  9. Wally

    Wally Telefied Ad Free Member

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    Donnie, the thing is that one end of that cap is soldered to the chassis. I think the problem arises when things go exactly wrong, and the cap shorts to chassis...with the wall voltage then being connected to the guitar player's hand through the cable from the amp and through the ground to the bridge and thence through the strings to ...you guessed it...the player. I have never seen it happen, but I don't risk it. There are no 'death caps' on newer amps.
     
  10. Donnie55

    Donnie55 Tele-Afflicted

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    Ok ...Thanks Wally... Guess I need to do that to my Princeton !!!!
     
  11. Billm

    Billm RIP

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    On a power transformer amp like this one, you can remove the death cap, but the amp may hum if the line cord is in backwards.

    I understand the desire to keep things completely stock on old amps, but in my experience, converting to 3-wire is the one thing that doesn't devalue an amp, especially if it's meant to be played, not admired from afar. And electrolytic caps are a maintenance item. Would you be proud of a 40-year-old car, boasting that you never changed the oil? or that the tires are rotted, but still mostly hold air?

    Not trying to attack, just keep perspective on old amps.
     
  12. cklingo

    cklingo Tele-Meister

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    Okay, here's a KILLER amp....

    I have a BEAUTIFUL, tiny, Supro Bantam. It is in pristine condition. Rocks like a mofo. The thing just kicks tone from a 6 inch speaker.

    The tubes are 50L6 and 12AX7. It appears to have no OT.

    So, is this a death cap-type amp? I never play this one because I'm concerned I'll get zapped. It would be an ultimate in-home tone monster. It sounds great and has a definite "tuxedo" vibe in appearance.

    Thanks! (I know, I need to get the camera out)
     
  13. tap4154

    tap4154 Doctor of Teleocity Ad Free Member

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    Heck, just have a three prong cord put on it. It won't change the amp, in fact my Champ has less hum after the new cord was installed (and death cap removed) by a local tech for $25. No more shocks either. It was always a crap shoot if I had it plugged in the right way before.
     
  14. sean79

    sean79 Poster Extraordinaire

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    You guys are scaring me. I just picked up a Guild Thunder 1 tube amp yesterday. Haven't plugged it in yet, but I'm itching to test it out. I'm guessing it has a 2-prong cord (made in the mid to late 60s).

    Do I need to be afraid of electrocution? What do I need to check? What the heck is a "death cap?"
     
  15. davidge1

    davidge1 Friend of Leo's

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    From Wikipedia:
    Keith William Relf (22 March 1943 - 14 May 1976), was best known as the lead singer and harmonica player of The Yardbirds.... was 33 when he died from electrocution, at his home, while playing his improperly grounded electric guitar.
     
  16. cbtd

    cbtd Tele-Meister

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    Getting shocked from an amp is no joke. I had a friend in High School that got shocked through his old Twin Reverb and a microphone. It knocked him out and he spent some time in the hospital.

    I've never gotten it that bad, but I got shocked from my 65 Bandmaster before I had a 3 prong installed in it, and I can tell you I needed to sit down for a few minutes and regroup.
     
  17. Billm

    Billm RIP

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    Yep, I've got one friend who has a rather nasty scar on his lip from his misspent youth as a guitarist/lead singer. Got up to the mic holding his guitar and next thing he knew, he was on his ass and his lip was smoking. Smoking.

    Another friend was working on an amp, guitar in hand, and touched another amp. He smacked his head on a shelf. When he regained consciousness, one eye was looking down 15 degrees relative to the other one. He still wears glasses with a wedge-shaped lens in one side to correct his vertical convergence.

    That amp with the 50C5 should be run through an isolation transformer.

    From what I can see, the Guild Thunder is a conventional, transformer-driven amp.
     
  18. lostpick

    lostpick Tele-Afflicted

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    Death Cap Explanation anyone?

    I have a old shocker that needs this cap removed also.

    What was that cap's original purpose?

    It went from hot leg to ground ?
     
  19. Wally

    Wally Telefied Ad Free Member

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    Are you sure there isn't one more tube in that amp labeled 35W4 or something like that? I am going to think that this Supro doesn't have a power transformer. The transformer that is there is an output transformer. There may or may not be an isolation tranformer there. IF there isn't one, then as BillM says there needs to be one there.

    Death cap....cklingo....In your second post, you list some brand names of soem old amps you own. Without a doubt, the FEnders and Gibsons have power transformers and death caps..unless soemone has done some modern mods to them.

    Grounded power cords are the cheapest method of reducing noise in an amp, as tap4154 notes. The safety factor is priceless. IMHO, you need a good tech to help you out with those amps.....or you need to do some serious studying so you can safely do this work for yourself. This advice is unsought by you, but I offer it with the best intentions. Live long......
     
  20. sean79

    sean79 Poster Extraordinaire

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    Thanks, Bill. What does that mean? When you say it's a conventional, transformer-driven amp, does that mean I'm safe? Are there precautions I need to take with this thing?
     
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