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This Little Amp Is Trying to Kill Me and My Girlfriend

Discussion in 'Shock Brother's DIY Amps' started by ArcticWhite, May 22, 2020.

  1. Jimclarke100

    Jimclarke100 Tele-Afflicted

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    I wasn’t there so I don’t have personal experience, but basically, they did. You’d likely be fine right until the point you touch a ground. I have seen many reports of people getting shocks from kit onstage and I’m certain that at least one fairly major musician was killed onstage when he touched the mic stand while playing through a faulty amp.

    Be safe...

    Edit. Looked it up; two that come up having died are Keith Relf of the Yardbirds, and Leslie Harvey from Stone the Crows.
     
    Last edited: May 23, 2020
  2. tubegeek

    tubegeek Friend of Leo's

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    Keith Relf - former Yardbird.

    Those two-prong amps had "death" caps providing an AC path to chassis ground for the leakage current, which I bet the amp in question does not have. And as you can tell by the name, they weren't entirely reliable.
     
  3. ArcticWhite

    ArcticWhite Tele-Afflicted

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    Thanks Rob.
    The power cord ground is already soldered to the chassis. The eyelet it is attached to is bolted, and soldered to the chassis.

    Question about the transformer leakage issue you mentioned: is this just how it was before grounded plugs and outlets? Meaning guys had significant current /potential on their strings?
     
  4. Hari Seldon

    Hari Seldon Tele-Meister

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    I'm glad you're not (fully) responsible for that mess ;- )

    But it would be highly advisable (and easy) to redo and isolate that stuff. Your grandchildren will thank you for it.
     
  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Dave: Well HAL, I'm damned if I can find anything wrong with it.
    HAL: Yes, it's puzzling. I don't think I've ever seen anything quite like this before. I would recommend that we put the unit back in operation and let it fail. It should then be a simple matter to track down the cause. We can certainly afford to be out of communication for the short time it will take to replace it.
    :lol::lol::lol:
     
  6. ArcticWhite

    ArcticWhite Tele-Afflicted

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    Obviously a human error.
     
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  7. Mongo Park

    Mongo Park Tele-Afflicted

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    Point to point is a great style of build I think the turret boards were made for quick assembly line construction in the true spirit of Leo and his desire/need to save a Dime to stay in business. It is a winning style if amp building.
    I think if you are going old school point to point to bring it up to date it is wise to use some shrink tube on your components. It will add a extra margin of safety to your build which is well worth Your time and cost is minimal. You can colour code so it is easier to follow things once it is built. B+ one colour and so on. I use purple on the signal path as it adds that extra sweet mojo tone that Jimmy would be proud of.
    I was told by a wise mentor use shrink tube. Make all joints mechanical as well as soldering them. Don’t connect components without some sort of support such as tag strips. Check your work at the end of a session which is way easier than hunting for that elusive mistake when it is all done.
    Downside is it is hell to take parts out if you make an error or do mods, but in the end your amp is less likely to bite you later on down the road after bumping around in the back of the car.
     
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  8. tdoty

    tdoty Tele-Meister

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    I wasn't there for the 60's, but in the 80s & 90s lots of us had AC on our strings........cuz we were using '60s & '70s amps in houses with old wiring and/or ungrounded 3-prong outlets. A shock through a mic stand, a mic, a buddy's guitar, or playing around barefoot on a concrete floor was not uncommon. A rug on the concrete helped.......my band built a riser in our practice space so that we were standing on wood and not concrete. It also brought the mic stands off the concrete. Only our PA was old, but all of us had dealt with old amps and floating grounds before, so we decided "better safe than sorry".

    The comment about the amp being "sloppy" (or however it was put) must involve not having much experience with old Silvertone amps........they are pretty sloppy looking inside. Heck, some of my building on eyelet boards is sloppy too. Sloppy isn't inherently unsafe.
     
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  9. tubeswell

    tubeswell Friend of Leo's

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    Did you fix it yet? The green wire going to the tab terminal appears to be meant to be a chassis ground. But it doesn't appear to be connected to the chassis. If you plugged in another 3-wire mains amp that worked properly, and this amp doesn't work properly, chances are its the amp and not the wall socket.

    (Sorry I didn't have time to read the whole thread yet to see whether you fixed it up properly)
     
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  10. BobSmith

    BobSmith Tele-Meister

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    Agreed, that’s certainly what it looks like.

    Someone upgraded the plug to a three-prong at some point without tying it to the chassis. While it would ensure polarity of the line voltage (hot would always go to fuse side), no other safety benefit would be realized with this “upgrade” left the way it stands.

    I looked at the schematic, and think it would be good (as in improved safety) to do this. A dedicated chassis mount is what I would do. You might get additional ground loop hum, but that’s a problem worth having and addressing later after safety is handled first.

    Anyone else see this differently?
     
  11. Asmith

    Asmith Friend of Leo's

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    Adding the safety ground shouldn't cause a ground loop, one will only occur if one is already built into the amp. The safety ground is a completely new connection connecting to something that isn't part of the circuit yet.

    And just because no one else has mentioned it, it's no good plugging into a GFCI if the G isn't connected. In the event something shorts to the chassis the GFCI detects the current and then trips the electric. And as robrob said without the ground you become the ground path which would be dangerous in the case of a fault.
     
  12. Bill Moore

    Bill Moore Tele-Afflicted

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    Back in the day, everyone knew the drill, hold the guitar and brush the back of your hand against your mic. If you get a tingle, rotate the plug.
    As far as the op's experience go's, lifting the chassis ground can cause the chassis to give you a shock to something that's grounded, (like his girlfriend), be glad you didn't kiss her before touching her first!
     
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  13. ArcticWhite

    ArcticWhite Tele-Afflicted

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    I know you guys haven't read through the thread, but I've mentioned several times that the green wire is grounded through that tab terminal. That terminal has its base bolted and soldered to the chassis.
     
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  14. ArcticWhite

    ArcticWhite Tele-Afflicted

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    I built the amp.
    It has always been grounded.
    20200524_091506.jpg
     
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  15. drf64

    drf64 Poster Extraordinaire

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    It's frustrating, and yet I can't look away. I keep coming back here to see, over and over again, advice for a problem that doesn't exist.
     
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  16. zook

    zook Friend of Leo's

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    Is the Black wire connected to the switch and the fuse, and the white (Neutral wire) attached to the PT?
     
  17. ArcticWhite

    ArcticWhite Tele-Afflicted

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    Black to fuse to switch.
    White to PT.
     
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  18. Asmith

    Asmith Friend of Leo's

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    I don't know how this thread hasn't been resolved yet. As far as I can tell your amp is functioning as it should. It just needs to be used with the correct outlet (a grounded one).
     
  19. drf64

    drf64 Poster Extraordinaire

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    @ArcticWhite is taking in all of the comments maligning his wiring, technique, and even, yes, sadly, his girlfriend with seeming equanimity. But all it's doing is fueling his anger. Oh, how I pity the fool....

     
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  20. tubegeek

    tubegeek Friend of Leo's

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    I tried to tell 'em.
     
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