(02-09-2018, 07:16 AM)skipjohnson Wrote: I have a early 1970's VT-40 with a two prong power cord. I want to install a 3 prong power cord, and remove the polarity switch and death cap.
Can anyone provide me a detailed description of the steps required?
I have attached a pdf of the physical and logical diagrams of the power section of the amp.
Appreciate your help.
Hi! Good call to install a 3-prong cord. There are a bunch of resources online that can help.
Here is one. There are also videos on youtube that are similar. I don't have VT-40, so I can't speak to your case specifically, but the steps are outlines in that article.
All the normal safety precautions apply. Don't kill yourself with the high voltage!
A tech will do this for cheap, so if the amp is due of any kind of service, you might just have them do this at the same time.
The things that I would emphasize in what you want to achieve are pretty simple:
1. You want the green (ground wire) firmly attached to something on the chassis. Usually this means soldering a ring connector and bolting it to a power transformer screw.
2. The black wire is the hot lead, and you want that to go to
both the power switch and the fuse. According
this schematic, it looks like it was wired that way originally, so you shouldn't have to do anything special when connecting black and white wires.
3. The cord itself should be secured well enough to make sure it doesn't get pulled out. Use a zip-tie to connect it to something handy.
4. You can just clip the leads to the death cap and polarity switch, and you should be good to go.
About the only thing that can go wrong is if your amp has multiple chassis grounds, adding one can result in a noisy ground loop. I've added grounded chords to all my ampegs without difficulty, but I don't have anything that is of a similar vintage, so maybe Hangman or someone will provide more model-specific info. Good luck!
