Silvertone twin twelve hums on channel two only

[dcline]

slight improvement...

Well,
I tried removing the reverb tubes and it made no difference. The hum does not change when you adjust or turn off the reverb level or the tremolo.
I did run a new shielded cable from the grid to the resistors that connect to the inputs and it made a noticeable difference. It's about half what is was. I also replaced the old carbon grid resistors with metal film resistors. The hum is still there but much quieter.
What puzzles me about all this is that I have another 1484 head that is completely stock other then the power supply caps were replaced and both channels are quiet as a mouse.
I too tried to contact Vibroworld with no luck. But the multi-can filter cap connects to both channels. If there were any issues with it, wouldn't channel one hum as well?
Just another reason that I ruled out the can cap.
The tuner cleaner on the tube socket is definitely interesting. All the tracing I did on the scope, the noise was right at the tube socket to the input. Everything else was pretty clean.
I was already considering putting in grounding jacks. That's next.
thanks again

[dcline]

???

Did the reverb still work at all?
The reason I ask is because the reverb works but is a bit weaker then my other amp with no hum.

[Mars Amp Repair]

D,

This may not be your issue, but I just realized the this is the very same amp that I had to add screen resistors to in order to stop some wacko parasitic oscillation in the power stage.

The original has no screen resistors & somehow the newer tubes can't tolerate that. It won't oscillate with old tubes.

I added 470ohm 5watt screen resistors & all was resolved. MIght be something to do to preclude possible future issues with certain power tubes.

There's another thread in here somewhere about this issue.

glen

[dcline]

Problem solved

Well,
I replaced the jacks on number two channel with new Switchcraft jacks and problem solved. What a learning experience this project has been.
Thank you everyone for the help!

[Garydean]

Nice!! Glad to hear everything is working again.

Gary

[ZombieMusic]

Hi,
I'm new to these forums here.

I also have a Silvertone with the hum on channel two. All of the problems w the amp align with all of the comments in the thread.
I was wondering what kind of Switch craft input jacks were used to solve the sound issue? shrouded or open frame? There seems to be two and I want to get the right one.
Thank you!
-Matt


"Well,
I replaced the jacks on number two channel with new Switchcraft jacks and problem solved. What a learning experience this project has been.
Thank you everyone for the help!"

[Randall]

There are well more than two types of Switchcraft 1/4" jacks, but the standard would be Switchcraft 12A. Jumper the leaf terminal to the ground terminal, this way the input is grounded with nothing plugged in.

[nevetslab]

Silvertone 1484 Schematic added

There are well more than two types of Switchcraft 1/4" jacks, but the standard would be Switchcraft 12A. Jumper the leaf terminal to the ground terminal, this way the input is grounded with nothing plugged in.

I've added the schematic for the 1484 Amp...not great quality though.

silvertone1484-1.pdf