Really need some help!!!!

[majsfel]

Hi, I'd really need some help with this.
So I have this Epiphone amp thats got alot of hum and seems to be having ground issues. Redid the filament wirings which helped alot but I still seem to have alot of hum and ground noise.
Opened it up while it was on and poke around with a chopstick and found this (see attached picture) that looks like a burned cable. It made a hell alot of hum when I poked around there with the stick. What does this cable do, how did it happen and how and can it be fixable? Worth to mention: The amp also picks up when I touch the guitar cable even at zero volume, it doesn't pickup the guitar until I roll the volume up though. (schematics: https://el34world.com/charts/Schematics ... eissue.pdf)

Epiphone.jpg

[LOUDthud]

Can't tell much from the poorly lighted pic you posted and the low quality schematic. Gotta see all those little numbers on the PCB. Where does the other end of the wire go ? A tube socket or the footswitch jack ?

What's the history of the amp ? Is it factory new or did some clown work on it ? From what I can see it just looks like a poor soldering job, not some kind of circuit fault.

[majsfel]

Can't tell much from the poorly lighted pic you posted and the low quality schematic. Gotta see all those little numbers on the PCB. Where does the other end of the wire go ? A tube socket or the footswitch jack ?

What's the history of the amp ? Is it factory new or did some clown work on it ? From what I can see it just looks like a poor soldering job, not some kind of circuit fault.

Screenshot_20230305_120215_com.android.gallery3d.jpg

It goes to the second pin of the 12ax7 tube socket. It's all factory except for the filament wiring which was really bad from factory (Epiphone even admitted it and published instructions how to change them)

[R.G.]

It goes to the second pin of the 12ax7 tube socket. It's all factory except for the filament wiring which was really bad from factory (Epiphone even admitted it and published instructions how to change them)

That helps a lot. I'm guessing here, based on back and forth with the photos and schematics, but it seems like that's the wire to the grid on the input tube. Looks like it's single-end-shielded on the PCB end, which is a valid thing to do.
And as L.T. said, looks like a poor soldering job.
If I were faced with this, I would first carefully re-solder that wire. If that doesn't help, there may be some other problem. Hum comes from many sources, and sounds similar even if there are several layered hums going on.

[LOUDthud]

It can be very difficult to get a stranded wire back into a hole on a double sided PCB once it is removed. That's what it looks like to me. If it were me, I'd try to remove all the solder from the hole in the PCB, then re-strip the wire to get as much of it as possible back into the hole before re-soldering. You may have to remove the PCB from the amp to accomplish this. An experienced PCB designer would design with oversized holes/pads to make repair easier.

[mhuss]

An experienced PCB designer would design with oversized holes/pads to make repair easier.

As if "repairability" is on any modern mass manufacturer's radar.

[Reeltarded]

They get a job and they try real hard!

[angelodp]

Try using a tiny amount of liquid rosin Kester 1544, on the joint, then with a properly heated soldering iron, remove the wires. Use a solder sucker to completely clean out the trace hole. Clean the wires with a solder sucker. Try to get all the solder off. Then wind the strands as tight as possible and lightly tin. Cut away the melted sheathing and replace with shrink tube. It's a bit of a fussy job but it can all be remedied....if that turns out to be the issue.