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. Hari Seldon

    Hari Seldon Tele-Meister

    Posts:
    246
    Joined:
    Oct 24, 2015
    Location:
    Germany
    I am not aware that "sloppy workmanship" is offensive or personal.

    Maybe it's not the right choice of words. If I offended someone because I used the wrong word in english I apologize.

    The solder joints on the pix would be a 1 or 2 on a scale of 10 (10 being the best). Thats plain to see (and could cause harm to the user).

    Maybe "poorly" would be a better word here?
     
    GoldDeluxe5E3 likes this.
  2. tubegeek

    tubegeek Tele-Holic

    Age:
    59
    Posts:
    952
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    Let's all take a breath here.

    @ArcticWhite - I think what you may be seeing here is some alarm at your outlet situation.

    Here are two pictures which show my house not burning down last week after an outlet shorted. Proper wiring and circuit breakers are nothing to sneeze at. Especially in the context of mains-powered high voltage DIY gear.
    The missing blade on the plug is welded into the shorted outlet. Possible cause - water may have gotten in there.

    IMG_20200515_175643_01.jpg IMG_20200515_175313_01.jpg
     
    Last edited: May 23, 2020
    jsnwhite619, ArcticWhite and sds1 like this.
  3. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    First, let me say that I was not offended at all by your post, or others like this one, because it's on topic, and I asked for opinions relevant to the amp itself. Thank you. I appreciate your time, your concern, and your criticism.

    I have a question:

    You mentioned ".. its mains power cable connected completely improperly..." Did you mean within the amp, or because I plugged it into an ungrounded outlet?

    I should note that many of these 1960's department-store amps made by Silvertone and Valco originally had two prong cords, and they lived in a world of two prong, ungrounded outlets. Many owners actually reached adulthood!

    That's the sort of outlet I plugged the amp into.
     
  4. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    Again thanks for your concern.
    The outlet in question is on a GFCI protected breaker. I promise not to plug an amp into it again, until it is a properly grounded outlet.
     
    awasson and tubegeek like this.
  5. Nickfl

    Nickfl Tele-Afflicted

    Posts:
    1,872
    Joined:
    May 24, 2016
    Location:
    Florida
    @ArcticWhite did you ever say if you had tried this amp in a properly grounded outlet? it kind of sounds like there's a short to the chassis somewhere but because you're using an on an ungrounded outlet, and there is therefore effectively no safety ground, there's no problem until the voltage on the chassis finds a route to ground, in this case through the guitar strings you, your girlfriend and then probably to the garage floor. If you plugged it into a grounded outlet it would probably trip the breaker if what I think is happening is correct. that being said I would be careful to you use a lightbulb limiter if you're going to test it on a grounded outlet because such a short can potentially damage your power transformer depending on what exactly is happening.

    IMO, the comments about the messiness of the build are only partially relevant to your problem. Layout is a red herring, point-to-point is inherently messy looking when done by most people but it is not in any way dangerous or problematic and those messy looking amps often function perfectly with fewer oscillations and less noise than a beautiful looking turret board build. Some of the solder joints are a bit messy and can definitely be prettier, but I don't know that I saw too many cold solder joints in there and in any case those are not a safety issue just might be an issue with signal quality and noise.

    The comment that is relevant, is the one that mentions all of the uninsulated leads that are exposed in there. Those are potentially a safety problem and very possibly causing the short that is giving you voltage on your chassis.
     
  6. The Ballzz

    The Ballzz Tele-Afflicted

    Age:
    65
    Posts:
    1,610
    Joined:
    Apr 11, 2016
    Location:
    Las Vegas, NV
    Electrical and other safety codes are not just a conspiracy by "The Man" attempting to ruin your day! The above pic from @tubegeek demonstrates that even when codes are followed, bad poop can happen. On the other hand, being wired properly probably saved his home from a much bigger catastrophe! That looks like an over current issue to me. Space heater or such?
    Glad You're Safe!
    Gene
     
    tubegeek likes this.
  7. tubegeek

    tubegeek Tele-Holic

    Age:
    59
    Posts:
    952
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    Thanks! Nothing drawing current at the time except a short as far as I can tell. No problems with any of the equipment plugged in. Possibly a fault in the extension cord, but I think water causing a short is more likely given the location in the wall.
     
  8. tubegeek

    tubegeek Tele-Holic

    Age:
    59
    Posts:
    952
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    Re: Codes and The Man.

    I actually had this thought while I was rewiring the outlet:

    Is there a Big Brass Screw cabal that lobbied for the requirement that dual outlets must be separable and have two connection points? Seems like a lot of unused screws sitting inside a lot of walls to me.
     
  9. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    I agree that the amp should always be properly grounded. Mea culpa.

    But what concerns me, is that people did it all the time in the 60's, playing through amps with two prong cords, and they didn't have AC on their guitar strings.

    When this amp is plugged into a properly grounded outlet it does NOT have AC on the strings. The only reason this ever came up is because I plugged it into my ungrounded outlet in the garage, and got a shock. I think that indicates a problem within the wiring of the amp - not within the outlet, grounded or not.

    And that's why I'm trying to fix it.
     
  10. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    Yes, I tested it on a properly grounded outlet and everything was fine. I should have mentioned that in the first place.
    Plugging it into the ungrounded outlet is what revealed the problem.
    I have to admit that the second half of your post is pretty much Greek to me.
     
  11. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    It's a PTP amp built by Silvertone, mostly. A lot of these old department store amps look like bird's nests. I just added a tone stack and MV.

    I'm aware that the soldering isn't beautiful, but none of the joints are cold.
    Bare wires are common in PTP amps and they aren't a problem unless they touch each other - which they aren't.
     
    sds1 likes this.
  12. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    Jeez, man that's a terrifying picture. Glad you and your house are okay.

    BTW, It looks like that j-box is pushed right against some pipes of some sort? Is that water, or just electrical conduit?
     
  13. tubegeek

    tubegeek Tele-Holic

    Age:
    59
    Posts:
    952
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    I've got hot water, cold water, drain, BX cable and **gas** all in that shaft. It's a 125-year-old house and not everything has been done optimally over that history for sure. When I list it like that it sure sounds awful!
     
    Verne Bunsen likes this.
  14. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    Yes, I've been using it on a grounded outlet since I built it. This whole thing just came up because I plugged into the ungrounded outlet in the garage and received the aforementioned shock.

    I'm beginning to think there's a short to ground in the power transformer.

    Those messy looking leads are actually pretty well separated in three dimensions. It's just the 2D picture that flattens them out. I'll go over it again though. Thanks for the tip.
     
  15. ArcticWhite

    ArcticWhite Tele-Holic

    Posts:
    829
    Joined:
    Apr 14, 2009
    Location:
    Portland Oregon
    I'd move that j-box for sure. I don't think it's good for metal conduit or j-boxes to touch water or gas pipe.
     
    tubegeek likes this.
  16. Lowerleftcoast

    Lowerleftcoast Tele-Holic

    Posts:
    938
    Joined:
    Dec 30, 2019
    Location:
    california
    I have been hearing about some odd issues with ground fault circuits. Is it possible when there is a current draw the GFI is causing this?
     
  17. tubegeek

    tubegeek Tele-Holic

    Age:
    59
    Posts:
    952
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    Well, not a whole lot of options in this space, but I hear you. If it makes you feel any better the disaster outlet was taken out of the j box and moved to the end of a few feet of BX up the wall. The j-box is properly covered, only has a junction in it, and the outlet box is the right type for wall mounting. So I feel like, if I'm not completely to code, I'm at least "to code-ish." I might GFCI the outlets too - they are not very far from the washer's water supply faucets and drain.

    Tell ya what - the thought of that box sparking right next to the gas line for my dryer DID scare the crap out of me, so, I'm thinking about ways to address the situation. Moving the outlets was a big improvement though.
     
    ArcticWhite likes this.
  18. tubelectron

    tubelectron Tele-Afflicted

    Posts:
    1,105
    Joined:
    Nov 25, 2010
    Location:
    France
    OK, then that's fine, @ArcticWhite. ;)

    Your power transformer doesn't show any (significant) leak, then. That simply means that the Greek (rather Tech, in fact :oops:) explanations I wrote are more or less met ! :lol: Grounding that kind of old devices is important, though.:cool:

    More simply : while being very abuse-resistant, as a power transformer ages, its internal insulation between windings and between core deteriorates slowly but surely, notably if the transformer has been widely used and moreover overloaded. :confused:

    Then the leaks appears and increases, the Xfo starts to overheat with time, even unloaded, and one of these days, there's smoke and the circuit breaker or the fuse does its job... Amen ! :(

    -tbln
     
  19. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,784
    Joined:
    Dec 29, 2012
    Location:
    United States
    The amp chassis is floating so leakage current from the power transformer can easily generate 50+ volts chassis-to-ground.

    Do not plug a tube amplifier into a non-grounded outlet--it is not safe. There is no safe path to ground for an accidental short to the chassis.

    Attach the power cord safety ground to the chassis ASAP.
     
    magic smoke, muscmp, BobSmith and 5 others like this.
  20. drf64

    drf64 Poster Extraordinaire

    Age:
    55
    Posts:
    8,197
    Joined:
    Jul 24, 2009
    Location:
    Ada, MI
    It's a little ironic that a guy whose machine tried kill him has an avatar pic of a killer machine.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.