'60 Tweed Fender Deluxe Ground Hum

[honkytone]

Have had a great old tweed Deluxe for many years, bone stock other than replaced filter caps and reconed speaker. And it still has the original two-prong power cord. I know, replace it with a three-prong, and if I were out gigging with the amp I would. But it mostly gets used at home and for now at least I'd like to leave it original.

It has no appreciable hum when on and in use, but it does get a ground-like hum when you take your hands off the guitar strings and aren't touching grounded metal on the guitar or amp. Once you put your hands back on it's fine. But with hands off and amp humming, neither throwing the ground switch nor reversing the two-prong plug makes the hum go away.

Wondering how to go about trouble shooting it. Could the cap on the ground switch be bad? I don't get shocked from the amp or anything.

I also have an original blackface Princeton Reverb, also with two-prong power cord and ground switch with death cap, and it's fine. That is, if it hums you can throw the switch or reverse the plug and the hum goes away. Would like for the Deluxe to work the same way.

'Preciate the help.

[Enzo]

Try a different guitar. You may have a ground wire off inside the guitar. At least we could then eliminate that possibility.



And throw the switch and turn the plug all you want, the amp STILL won;t be grounded. SOme amps will be relatively OK that way, others won;t


You get shocks from ungrounded amps when YOU are what is grounded and the amp is not. WOn't usually get shocks on carpet. Does the ground switch make ANY difference in hum ever? If so, then it probably is working.


For the price of a power cord and 10 minutes work, you can eliminate a variety of hum related problems from occuring in the first place.

[honkytone]

Thanks for the reply. Doesn't matter which guitar--humbucking, single coil--this is AC hum, not input related. Again, hum is gone as long as you're touching the strings or chassis. Ground switch doesn't ever seem to make a difference, nor does reversing the power plug. That being the case, why should I expect it to be different if I install a three-prong power cord? Yes, the amp would be "grounded" and safe, but might I not still get the hum when taking hands off the strings? And if so, why?

[Gtr_tech]

More hum when you aren't touching the strings is normal with passive p-up guitars. Thats just the way it goes....

[honkytone]

More hum when you aren't touching the strings is normal with passive p-up guitars. Thats just the way it goes....

Yeah, I know, I'm an old timer, too, going on 40 years at this racket. But this is more hum than a comparable amp with a comparable power cord and ground switch setup. My tweed Champ, blackface Princeton Reverb, Gibson GA-75, et al....all with a ground switch/death cap, all with two prong cords...none of them make this much hum when taking the hands off the strings.

[Enzo]

Grounding makes amps safer, but it also references them to the earth.

Here is a simple test. You have grounded outlets? DO you have some other amp with a three wire cord? If so, plug that other amp into the wall. Plug your two wire amp into the wall also, and turn it on. The three wire amp doesn;t even have to be turned on, we are only using it for its ground. Sit them near each other. Now take a piece of wire, and touch one end to the grounded amp, and the other end to the chassis of the two wire amp. If I do something like this I usually touch them on the jack nuts, which of course are grounded to chassis and convenient. If touching this wire to the two amps (which then connects the two wire amp to ground through the wire and other amp's ground) reduces this hum situation, then the need for a ground is made evident. If it affects nothing, then I was wrong.

[honkytone]

Thanks for that clear and simple test. The tweed Deluxe is in fact quieter--as if hands were touching strings--when it shares a ground with a 3-wire amp. Clearly it'll be worthwhile to install a 3-prong power cord, so that's what I'm going to do at my first opportunity. Thanks again.