grounded plug for my bassman?

[dirty]

I have a Fender Bassman Ten, a 4x10 bass amp from the early 70s. It has a three prong plug, but the ground pin has been pulled out. It also has a ground switch, and what I think is a "death cap".

Can I safely snip off the existing plug and attach a new one, with a ground pin? The whole point would be to make the amp safer, but what should I test before I do this?

Test for continuity between the ground wire in the cord and the chassis? The schematic shows a three prong plug, so I've been assuming this would work. Any opinions?

[rockstudio]

Here is a likely scenario for your missing gound pin: the amp's previous owner had ground loop problems, he addressed them by defeating the ground connection from the amp to the earth. I doubt there was any circuitry reason for removing the pin. A lot of ground pins simply get broken off by accident. I would replace the "edison" (A/C plug) straight away. This month there is a very good article about amp and guitar shielding and grounding in a different recording mag from the UK. If you are really concerned, take you amp to your technician and have hime look it over and replace the edison. Remember, Safety is No Accident!

[dirty]

that's what i figured.

I only wondered about an amp with both a grounding switch and an edison plug....

[Scodiddly]

It was common in the 70's to have a grounded plug but also all the old polarity switch and death cap stuff in the same amp. The good news is that it's easy enough to fix.

Go ahead and put a proper 3-pin grounded plug on the cord. Longer term you'll want to have somebody look at the innards and make sure there's nothing dangerous in there.

[dirty]

thanks a lot guys!

[rockstudio]

there is also a method for removing your grounding switch. I can't remmeber where I saw it, maybe the groove tubes book?? It tells you the correct way to wire the A/C to the power switch after removing the polarity switch.

[???????]

fix your plug and clip off the death cap. It's easy. I recommend discharging your filter caps before poking around inside an amp. The process can be broken down into two easy steps:

1. Locate the death cap
2. Clip it off.

The end!

[???????]

for advanced types:

Try routing the negative feedback of your amp through teh now-defunct ground switch. Take the wire that goes from the circuit board to the ext. speaker jack. Insert the ground switch in-line with it so that you can open or close that part of the circuit. Congratulations, your ground switch is now a NFB/no NFB switch. Or a "polite/rude" switch. Or a "blues/jazz" switch. Or a "raw/refined" switch, or whatever you want to call it! totally reversible mod. I did this in my BF deluxe.

[dirty]

can i admit something.... i don't actually know what makes the death cap so dangerous. what is it? and why would it be there at all?

thanks again for the advice, and brad347, that sounds like a sweet mod. I'll try it!

[brianroth]

One end of the death cap connects to the chassis, the other end to one side or the other of the AC mains line, depending upon the setting of the "ground" switch.

If the cap fails with leakage (or shorted), then the chassis is connected directly to one side of the AC mains line.

Bri

[jetboatguy]

My friend purchased a vintage Bassman amp in the same state... broken ground lug... and I would get an AC lift when plugging my electric guitar into the amp... so I simply re-installed a uggly yellow Leviton plug with proper ground connection to the existing 3 wire AC cable... and voila, no more shocks... quite a discomfort when your body is acting as the actual ground conductor !?

[dirty]

Lucky for me, I haven't been shocked yet. But it definitely seemed less safe than it should be, and I let friend's play through it as well, so it seems like a good idea to make it safe right away.

Also, it got bit by a power spike, so I figured I should do any work on it now, while it's out of commission anyway.

Just for the record, I love the amp. Great chunky bass tone, and I love pushing it a bit with electric guitar. When I finally build my reamp, I'm gonna put some drums through it cranked up!