Adding a 3 prong cord to an amp

[Joshua Levin-Epstein]

This is being motivated by a remark made in regard to the Silverface pro reverb. A long time ago, the first time I was unemployed, I modified my Airline GDR-9013A, replacing the on off switch with a polarity switching on-off-on switch and a grounded plug. I tied the ground to the chassis and the other prongs to whatever the two prong cord was tied to. When I was working on that stereo white falcon, i discovered what I imagine was a ground loop when using a second amp. The hum disappeared (or lessened) when I lifted the ground on the Airline via a grounding adapter. The polarity switch never made a tremedous amount of difference. I was tempted to change the amp back to original, but the grounded cord does seem to make sense.

 

So what did I do wrong, if anything, and what should I do?

 

And to save Paul the trouble, attached is a schematic.

 

Joshua 

[Mark Pollock]

I have a very strong opinion about this, and my argument goes like this -

Clubs, stages, and gatherings all have electrical sources that are out of your control. When you hook up an electric guitar to an amp at one of these places, you are connecting your hands, via the strings, to whatever that location has hooked up for electricity. You are then touching other objects, such as microphones, stands, whatever, with other parts of your body. Stories abound of people getting shocked, either mildly or severely, by these things. It can be deadly.

My solution - just go wireless already. No cables to trip over, no chance of being shocked by your guitar, and also much less hum from your pickups. If I was gigging again, I would use a wireless exclusively, and never have to worry about how some boyfriend of a waitress went and hooked up all the outlets backwards and upside down and neglected to actually hook the ground wire up to something.

Okay, here's one guy's way of doing it, and he deals with the "death cap" correctly.

http://www.theguitarfiles.com/guitarfile644.html

But I'll say it again - just go wireless, and you will NEVER have to worry about sparks shooting from your lips while playing a guitar and singing.

[Paul Verticchio]

Thx for the nod Josh (-:

When it comes to issues like this, I refer my customers to an experienced & expert amp tech in a town right down the road His name is Mark Tate and he owns & operates the Luthier Shoppe in Springfield, IL.  His # is 217-546-1615. As is usual in the trade, he loves to talk shop. Give him a call.

My electronics adventures end once the voltage exceeds 24vDC (-:  That's  the voltage where my personal "bravery" ends due to lack of hands-on experience.

Have a great week,

Paul (-: