# shocks and hum from old amp?



## devnulljp (Mar 18, 2008)

I have an old Silvertone amp-in-case guitar. The amp in the case is only a little 3W tube amp, but I'd still like to be able to use it. It has a bit more hum than I'd like and something nasty going on with the electrics -- put any pedal plugged into a power source in it and it buzzes and hums something nasty, and you get little shocks off the jacks. Something's maybe not grounded right (or at all). Where should I start looking? It's only a two-prong plug My guess is that's the first thing that needs to be fixed?

There's a pic here: http://farm4.static.flickr.com/3172/2752571544_a3f79e8505_o.jpg


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## Geek (Jun 5, 2007)

Hi,

Good chance it's rectified line opped with no isolation transformer and the "cap of death" is leaky, along with a dried out filter cap causing the hum.

It needs line isolation before proceeding with other repairs, IMO.

Cheers!


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## devnulljp (Mar 18, 2008)

Geek said:


> Hi,
> 
> Good chance it's rectified line opped with no isolation transformer and the "cap of death" is leaky, along with a dried out filter cap causing the hum.
> 
> ...


OK, that sounded like a reading from Finnegan's Wake to me, or maybe the Jabberwocky, so I guess I need to take it to see an amp tech 
Thanks


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## bolero (Oct 11, 2006)

yeah I wouldn't use that amp & handle anything else plugged in, you could get a nasty shock or even killed


those are dangerous

an isolation transformer would be the way to go


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## Ripper (Jul 1, 2006)

all good advice. 
If you happen to need an iso tranny after having the amp fixed drop me a pm.


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## devnulljp (Mar 18, 2008)

bolero said:


> yeah I wouldn't use that amp & handle anything else plugged in, you could get a nasty shock or even killed
> 
> 
> those are dangerous
> ...


I plugged in my echoplex and got a wee jolt when I went to plug the cable into the guitar, so I turned it off and unplugged it. 
Thanks for the advice. Think I'll leave off until it's been looked at.


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## Ripper (Jul 1, 2006)

devnulljp said:


> I plugged in my echoplex and got a wee jolt when I went to plug the cable into the guitar, so I turned it off and unplugged it.
> Thanks for the advice. Think I'll leave off until it's been looked at.


On those amps, even having the caps done etc, probably won't fix the shock issue. As was mentioned, these amps are probably like alot of the ones from that era that don't use a power transformer. I've got a couple of garnet made stencil amps (one made for eatons, the other a united) that are the same way. Great sounding little amps, but you just have to be careful with them.


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## devnulljp (Mar 18, 2008)

Ripper said:


> Great sounding little amps, but you just have to be careful with them.


What does that entail (other than not standing in a pool of beer while playing...)? I love the guitar, but obviously that can be played through my other amps. I like the novelty and vintage kitsch of the amp-in-case, but don't like the idea of getting shocked -- I wonder what that loose current is doing to my gear too. I'll definitely have it fixed up, but if it's always going to do that, I might just never use it.


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## Wild Bill (May 3, 2006)

devnulljp said:


> What does that entail (other than not standing in a pool of beer while playing...)? I love the guitar, but obviously that can be played through my other amps. I like the novelty and vintage kitsch of the amp-in-case, but don't like the idea of getting shocked -- I wonder what that loose current is doing to my gear too. I'll definitely have it fixed up, but if it's always going to do that, I might just never use it.


The caps have to be replaced, regardless. Just to get rid of the power supply hum, if nothing else. The "death cap" is a cap used in the internal grounding of the circuit. If it gets old and leaky it lets AC from the wall flow on the chassis of the amp. That's why you're getting shocks. Replacing it should fix this.

After all, people in the 50's did not get constantly shocked from devices with no power transformer to provide isolation. That would have been just silly and no one would have bought these things.

Still, the best repair involves a small power trannie being "shoe-horned" into the case. Any competent tech should be able to do this for you. 

:food-smiley-004:


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## Ripper (Jul 1, 2006)

and don't play it while standing on bare concrete.


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## Geek (Jun 5, 2007)

Ripper said:


> and don't play it while standing on bare concrete.


Or in a puddle...
(hey, it IS the wet coast :wink: )


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## devnulljp (Mar 18, 2008)

Geek said:


> Or in a puddle...
> (hey, it IS the wet coast :wink: )


What about concrete under an inch of water? At least is wouldn't be bare concrete. hey I have life insurance; if I died I could afford a '59 ES335...


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## traynor_garnet (Feb 22, 2006)

I have a perfect Iso Tranny for you. PM me if interested.

TG


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## Geek (Jun 5, 2007)

devnulljp said:


> What about concrete under an inch of water? At least is wouldn't be bare concrete. hey I have life insurance; if I died I could afford a '59 ES335...


Perfect picture for the cover of an album... you stanfing knee deep in the Georgia Strait, holding your guitar plugged into the zap-amp :banana:


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