[WannabeGood]

Heres the deal, actually two parts:

I need to replace the fuse holder (cap disintegrated) on a 60's vintage Silvertone 1471 amp. Should I replace the two wire power supply cord with a three wire grounded cord and if so where should the ground wire terminate on the amp chassis? Thoughts on this?

Cheers,

 

[Wild Bill]

Heres the deal, actually two parts:

I need to replace the fuse holder (cap disintegrated) on a 60's vintage Silvertone 1471 amp. Should I replace the two wire power supply cord with a three wire grounded cord and if so where should the ground wire terminate on the amp chassis? Thoughts on this?

Cheers,

Absolutely, if you are already inside the amp to replace the fuseholder then you should replace the old 2-wire cord.

The "inspector approved" ground point would be something mechanical and all by itself, meaning not a shared ground point. Typically we put a crimp-on ring terminal on the green ground wire. Crappy Tire is selling kits with a proper tool so cheap they almost pay YOU nowadays! Use the tool, don't make a mess out of it with sidecutters. Put it under one of the mounting bolts for the power transformer. Use some lockwashers. There are nuts out there with a lockwasher built right on them but I've never seen them in a hardware store. If you scrounge old gear you can build up a good salvaged stock of such hardware.

If the tranny bolt is not convenient then maybe you could drill a hole and put a nut and bolt (8-32 works fine) in just for the ground terminal.

Now, do you have a ground-reverse switch that has become redundant with that new 3-wire cord? If so, disconnect it and remove the "death cap" from its common terminal to ground. If you don't it could possibly bite you badly some day.

Now, let's start dreaming of some neat mods to use that switch...:smile:

:food-smiley-004:

 

[WannabeGood]

Wild Bill,

Thanks for your iput. I've got a crimping tool and terminals and think I'm skillful enough to wire in a new cord but could you expand on the "ground-reverse switch" and "death cap"? Sounds potentially painful. I hate pain.

Regards,

 

[Wild Bill]

Wild Bill,

Thanks for your iput. I've got a crimping tool and terminals and think I'm skillful enough to wire in a new cord but could you expand on the "ground-reverse switch" and "death cap"? Sounds potentially painful. I hate pain.

Regards,

Most amps from the 2-wire era had a "ground reverse" switch. It was a single throw double pole switch that would toggle a bypass cap from either side of the power wires to ground. One position or the other would mean less hum pickup with the amp.

The reason it's nicknamed the "death cap" is that if the cap failed and shorted you had a 50% chance of the hot power wire shorted to the metal chassis/frame. If you were standing on something grounded like a wet basement floor you could get full line voltage through YOU!

This didn't happen often but man, could it hurt! If you had a heart problem who knows what could happen.

With a 3-wire cord that hard-grounds the chassis you don't have this worry. You also don't need a ground reverse switch anymore but if you leave it connected to your power wires you will still have the cap bypassing one wire or the other to ground. So you've put on the new cord but still have the death cap hazard!

So you disconnect the wires running to the switch, including the cap. Sometimes you might have to do a bit of new wire or splicing depending on how the amp was wired. If you take out the wires to the switch you might be breaking the power to the amp. The quick and easy way is to simply clip out the death cap. Then it doesn't matter if the switch is still there or not.

But as I had said, if you disconnect the ground reverse switch and re-wire the power properly you now have a perfectly good switch sitting in your amp that could be used for a neat mod...

:food-smiley-004:

 

[WannabeGood]

Many thanks for sharing your experience and wisdom.

Haven't I heard (read actually) that somewhere before?

Regards,:bow: