Stupid amp question....ground switch

[rockinlespaul]

I have two amps with a ground switch on the back panel. One is a '72 Bandmaster Reverb, the other a '69 Traynor PA head.

My question is....is this switch supposed to be in the ground position, or the other way? :jo

Switch is at the far right in the pic....

http://img.photobucket.com/albums/v56/agriv8n/000_1374.jpg

[John Phillips]

If the amp has a 2-wire cord, get it converted to 3-wire as soon as possible - it's a safety hazard with no ground wire and a functioning ground switch.

There is no 'right' way for the ground switch - it depends on where it's plugged in and/or any other equipment connected. Despite its name, the switch does NOT ground the amp - what it does is to use one of the supply lines as a 'pseudo ground' for noise reduction, NOT safety. It's inherently dangerous because it's possible for the amp to become live.

If it already has been fitted with a 3-wire cord, the ground switch should have been disconnected and doesn't do anything.

[rockinlespaul]

Thanks for the informative answer John. Both amps have had a updated cord, so I'll assume the ground switches have been dissconnected.

[WaltC]

I wouldn't assume anything. I've worked on lots of amps that have been "converted" to three prong plugs where the "converter" just wired in the new cord to the same contacts that the old cord used and either soldered or bolted the new ground wire to the chassis/transformer bolt.

I've also seen several new amps, built with 3-prong plugs initially that incorporated a ground switch to do basically the same thing the old-style switch did as far as reversing polarity of the incoming hot/neutral wires.

So just because it has a 3-prong plug (I even worked on one amp that someone had added a three prong plug to a 2 wire cord with *no* ground/green wire AT ALL), don't assume without checking or having your tech check, that it's been installed properly.

My 2¢ <G>

[rockinlespaul]

I wouldn't assume anything. I've worked on lots of amps that have been "converted" to three prong plugs where the "converter" just wired in the new cord to the same contacts that the old cord used and either soldered or bolted the new ground wire to the chassis/transformer bolt.

I've also seen several new amps, built with 3-prong plugs initially that incorporated a ground switch to do basically the same thing the old-style switch did as far as reversing polarity of the incoming hot/neutral wires.

So just because it has a 3-prong plug (I even worked on one amp that someone had added a three prong plug to a 2 wire cord with *no* ground/green wire AT ALL), don't assume without checking or having your tech check, that it's been installed properly.

My 2¢ <G>

Alright...going along those lines then, if it IS still hooked up, which way should the switch be going?

[brad347]

It should really be disconnected for maximum safety.

And if the 3-prong plug is properly installed, it will have no effect either way.

[mbratch]

I have two amps with a ground switch on the back panel. One is a '72 Bandmaster Reverb, the other a '69 Traynor PA head.

My question is....is this switch supposed to be in the ground position, or the other way? :jo
Actually, the ground switch is usually mounted so that it toggles left/right so there is no position that is toward the word "ground". Not sure why yours is mounted up/down (unless some of the Fenders did that (?)).

I agree with the comments about 3-prong plug.

[rockinlespaul]

Thanks guys.:AOK

[Johnny Z]

Forget all that BS, how many guitarist have been eletrocuted playing guitar in the last 50 years? Sure there are a few but you have to do more than just have a bad ground for that to happen. What you really want is all the equipment grounded the same and with the primary (Black) side to the power supply. If you get too much buzzing then most the time something is grounded in reverse and you get a ground loop. Some amps with 3 prong plugs also have a 3 way ground switch, like my '75 Twin Reverb, I think the middle position is a ground lift and the other sides reversed ground, seldom have I ever even moved the switch to correct a ground fault. The only times I've been shocked playing guitar and singing into a mic is when someone had the PA ground reversed or standing on a cement floor in my bare feet in my "garage band daze" with a reversed ground. If you only have a 2 prong plug and no ground switch like on many old amps without a polarized plug, just reverse the plug it to correct the problem. A three prong plug is a good idea to have installed but some vintage collector's would prefer the original 2 wire setup. If you really want to be safe hook up a GFCI.

[brad347]

Forget all that BS, how many guitarist have been eletrocuted playing guitar in the last 50 years? Sure there are a few but you have to do more than just have a bad ground for that to happen. What you really want is all the equipment grounded the same and with the primary (Black) side to the power supply. If you get too much buzzing then most the time something is grounded in reverse and you get a ground loop. Some amps with 3 prong plugs also have a 3 way ground switch, like my '75 Twin Reverb, I think the middle position is a ground lift and the other sides reversed ground, seldom have I ever even moved the switch to correct a ground fault. The only times I've been shocked playing guitar and singing into a mic is when someone had the PA ground reversed or standing on a cement floor in my bare feet in my "garage band daze" with a reversed ground. If you only have a 2 prong plug and no ground switch like on many old amps without a polarized plug, just reverse the plug it to correct the problem. A three prong plug is a good idea to have installed but some vintage collector's would prefer the original 2 wire setup. If you really want to be safe hook up a GFCI.

Yeah. And how many people have actually DIED from lead paint? Let's all go eat some!!

[Johnny Z]

Yeah. And how many people have actually DIED from lead paint? Let's all go eat some!!

Not the samething, but if you like I can supply you with some battleship gray from about 1945.



:messedup