Tube Amp Hum??? Help!

Larry Jamieson · Post by **Larry Jamieson** » 8 Jun 2004 6:42 am

A fellow recently brought in a Gibson Explorer tube amp, looks like something from the 60's maybe. It works OK, but it hums. Is this something easy to fix? Appreciate any help or suggestions. Thanks, Larry Jamieson waltonmusic@yahoo.com

Jay Fagerlie · Post by **Jay Fagerlie** » 8 Jun 2004 6:53 am

Plug in a regular 6 string guitar, play an Ab (G#) on the 6th string (fattest) and slowly bend up a half step.
If you hear the beats, it's power supply hum, get a cap job.
Cap jobs are pretty routine, especially for a vintage amp.
Good luck!

Jay

C Dixon · Post by **C Dixon** » 8 Jun 2004 7:02 am

Jay is probably correct. But before you go this route, a tube with a heater to cathode leakage can cause a hum also. I have not a clue where one can find a tube tester nowadays, but if you can, they can find this type of problem. But again, Jay is more than likely correct.

carl

Ray Minich · Post by **Ray Minich** » 8 Jun 2004 9:22 am

If it's from the '60's and it has the original capacitors in it, it's a tribute to the cap mfgrs that the amp starts at all without shorting the 5U4 to ground with excessive cap leakage.

Who knows, if you run it for a while maybe the electrolytics will reform and things will quiet down. Look for blobs of wax that may have extruded from the filter caps.

Hiya Carl

[This message was edited by Ray Minich on 08 June 2004 at 10:23 AM.][This message was edited by Ray Minich on 08 June 2004 at 10:24 AM.]

Larry Jamieson · Post by **Larry Jamieson** » 8 Jun 2004 6:22 pm

Thanks for the help, gentlemen. I may try to sell it as is. If that doesn't fly, we'll talk to some amp techs in my area and go from there. Regards, Larry Jamieson

chas smith R.I.P. · Post by **chas smith R.I.P.** » 9 Jun 2004 9:33 am

I always explain that it's not a regular hum, it's a vintage hum, which has a more pleasing warmth to it.....