'66 Vibro Champ grounding.

[jrgtr42]

So I have a 1966 Fender Vibro Champ that lately has been giving me a buzz if I touch something else at the same time.
Obviously a grounding issue. I pulled the chassis to see if there was anything obvious sticking out, and didn't see anything.
It is still the old two-prong plug. I've long said I need to convert to 3-prong, but I'm unsure what to connect where.
Can anyone give me some pointers? (or a good amp tech in the west-of- Boston area?)
Looks like one lead goes to the fuse, then grounded through the blue cap? and the other to the power switch.

 

[PaulD]

The capacitor connected between the mains and ground is what is commonly known as the "Fender death cap". If that capacitor were to fail short circuit, which is a fairly likely prospect for a 55 year old capacitor, then dependant upon which way round the plug is inserted could mean that the chassis of your amp is live with mains voltage. Some info on "death caps" here https://robrobinette.com/Death_Cap_and_Ground_Switch.htm

For basic safety reasons these should always be replaced with a proper 3 wire cable and the chassis correctly grounded. With the greatest respect and as you say that you are unsure what to connect where I would strongly suggest leaving this to someone who knows how to do the job properly and safely. There are are lots of potential hazards inside a valve amp, even long after it has been unplugged there are capacitors in there that will have enough energy stored in them to give a fatal electric shock and I have seen many instances of DIY repairs and modifications that are downright dangerous.

 

[poor man's burst]

What the hell is this Mallory can-cap doing in this place?!? It looks like your Vibro Champ has been messed by some butcher. I share PaulD's advise to bring it to a competent tech to have it properly serviced.

 

[PaulD]

Yeah I did wonder about the can cap. Looks like the original chassis can is still wired in place so I would hazard a guess that someone has just wired that in parallel to avoid replacing the original. Definitely a bodge job!

 

[Wally]

Got a tech? IMho, the cap can needs to be properly placed where the original was left.
+1 on a grounded AC power cable And removal of the death cap. The hot needs to run through the fuse to the switch to one end of the PT primary. The neutral should run directly to the other end of the PT primary.

 

[jrgtr42]

I do know my way around an circuit diagram, and me and my soldering iron are old pals, but I was kinda thinking a pro is the way to go.
Unfortunatly, the ones I've known in the area are out of business, some for quite some time.
I don;t particularly want to start shipping amps all over the country - I have a couple / few others that are probably going to need to be looked at in the fairly near future.
Guess I'm going to make a few phone calls tomorrow to see if anyone I know knows any amp guys locally.

 

[corpse]

I see guys advertising on Craigslist in the Boston Plymouth area- worst case there is a guy in Providence- there's another guy right here in Dennis that does tech work but that is probably a shag.

 

[corpse]

BTW- I had a '63 Deluxe that had one of the brass-looking uninsulated wires come unsoldered- that would be an easy fix. But still get that cord changed- and a cap job will sweeten it up and make it more authoritive.

 

[jrgtr42]

I see guys advertising on Craigslist in the Boston Plymouth area- worst case there is a guy in Providence- there's another guy right here in Dennis that does tech work but that is probably a shag.

A friend of mine uses Frank's in dennis - but he goes to Chatham at least once a month, more like every couple weeks in summer.
I'm not down there too oftem. There's another one I found, Sterling amps in Sterling, which isn't too far.
when I get a minute this afternoon I may put in some calls to the local shops to see if they recommend anyone - as far as I know none of them do in-house amp repair, just guitars and such.

 

[corpse]

call Mark's Guitar Loft- he is a good guy and will know someone