Hum problems from a Hot Rod deluxe

[g1]

There is a 10ohm resistor (R63) from the input ground to the pot bracket ground, check that it is ok. Any chance of a burnt ground trace on the input jack/pot board? Also make sure the pot nuts (if it has them) are tight.

[JoeM]

If you plug in a guitar, does the guitar's volume control have any effect on the hum? (in either jack)

[bsco]

Thanks very much for the ideas. It looks as if the jacks are direct replacements...they are not "hand wired" to the circuit board and the solder connections are good..I checked that out. I also had thought of a bad ground in the first tube stage but couldn't find anything wrong....and there is no broken wires in that grey interconnecting cable between the mainboard and the small seperate circuit board that has the 1st tube. I had checked the high voltage supply for ripple and found it to be clean. I didn't think of checking the low voltage rails. I will most definately check it out and let you know what I find.....or don't find. I did put a jack into the pre-amp out and you can see the hum on a scope and can turn it up and down with the volume control for the clean channel and if you engage the drive channel, then that volume control will also turn the hum up and down. So is it correct to assume the problem is isolated to the first tube stage?? Then again, assumptions usually get you in trouble. I will modt definately check out the low volatge rails shortly.Thanks very much.
Bernie

[Jazz P Bass]

Missing ground connection somewhere? Did you check the replaced jacks to verify they were installed correctly? Are they direct replacements, or did someone wire a non pcb mount type (like a Switchcraft) and run wires to the PCB?

Good call on that
Seeing that the volume control changes the hum, that says that the problem is before the volume control.
You may want to verify that the IC's are getting there proper voltage.
Pin 4 (-Vdc) & pin 8 (+Vdc).
There should be very little (ie: none) Vac ripple on those two rails.

[JoeM]

...
. Looks like there are new input jacks installed.....

Missing ground connection somewhere? Did you check the replaced jacks to verify they were installed correctly? Are they direct replacements, or did someone wire a non pcb mount type (like a Switchcraft) and run wires to the PCB?

[bsco]

Hi. New to the form....however I have been viewing it for some time now and have decided to join up...Hopefully I can be of some help to members and they can be of some help to me as well...I am trying to repair a Hot Rod deluxe for a friend of mine which has a very bad hum problem which can be adjusted with the volume control....turn down the control and the hum goes away, turn it up and the hum gets louder the higher you turn the volume control. If you kick in the drive and more drive functions, then this hum becomes unbearable. New tubes, one new power supply cap,lots of bad connections, etc...replaced the plate load resistors because the amp was cracking.The amp has lots of volume but can't get rid of this nasty hum. It has dual 6l6's in it. The hum is there even without an instrument plugged in. Looks like there are new input jacks installed......Checked out the 47 uf/16V capacitor for leakage in the first stage......tested ok. Anybody got any ideas????I am open to any and all suggestions no matter how simple or bazzare they may seem.
Thanks.