This is actually why I took the Paleoelectronics.com domain in the first place. I got tired of hearing how an amp tech had cut out the old 2 wire cord from a classic amp to make it safer.
You certainly need to get an earth ground hookup in these old two wire amps, but you don’t have to ruin the resale value of the amp to do it.
Here is how I do it, I take a small plastic project box and stick a 2 prong receptacle on one end, a three prong (IEC) receptacle on the other end and I pull out the earth ground wire and solder it to the PT chassis ground.
Here is a dumb diagram :

Doing this means you can leave the old plug in place, assuming it is not frayed and dangerous. You still get the benefits of 3 Prong safety, assuming you do a good job of soldering the earth ground (the half round part of the 3 prong plug) to the chassis. I did this at the ground wire of the PT. Don’t go alligator clipping this thing on or anything stupid like that. If it gets loose, you have a good chance of blowing something.
Now you can use a standard 3 prong computer power cable, and just plug the two prong plug into the other end.
This and removing the death cap will make your amp much safer, but it does have a drawback. You will now discover how well your amp is grounded. My GA-5 Crestline is pretty well star grounded but I still get some popping when I touch the strings.
Thanks for the info! Could you post a pic of your finished box? Do you run the ground wire through a hole in the box to the power transformer chassis ground? What gauge wire do you use for that, and also for the other connections?
Thanks!
Death Cap & 2 prong power cords - Caution ! - My Les Paul Forums // Aug 23, 2010 at 12:04 pm
[...] Ampeg VT-22 has a 2-prong plug. I'm considering doing something along the lines of the following: 3 Wire ground your amp without ruining it's value. To the experts out there: Does this seem safe? I've got other questions, too, but I'll save those [...]
@JustAGuy
Sorry.. I sold the amp with the box, but that is exactly what I did. Popped an extra hole in the box, put in a grommet and pulled it into the chassis via the same hole that brought in the power.
I used 18ga solid wire for everything, IIRC.
Thanks, Dilapidus! Could you elaborate a little further about what exactly has to be done to disable the death cap? Do you just snip it out and you’re finished, or do you have to re-wire the polarity switch or something else?