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TH30 Effects Loop Ground Issue

Posted: Sun Mar 03, 2019 6:42 pm
by chrisliua
Hello all,

Long time lurker and orange amp fan, but first post.

I have had a TH-30 for years that I never play, just didn’t gel with it and planning on selling. When testing everything out I found the effects loop makes a really loud (not normal pedal hum or hiss but audibly louder than I play) static noise.

I known others have experienced effects loop issues on the TH-30, and I have tried the recommended trouble shooting tips: plugged a single cable in the loop, used contact cleaner on the jacks. Even after doing both I still get the noise. When I plug in a metal ended patch cable, the noise does go away, but when I touch the metal on the cable sticking out of the jack it comes back, almost as if I was touching the tip on a cable plugged into the amps input.

This definitely makes me think there is some kind of short between the hot and the ground in one of the loop jacks.

I have experience working on and missing amps, so comfortable opening it up to take a look, just wondering if anyone else has opened one up to diagnose this problem, and if so, any tips?

Re: TH30 Effects Loop Ground Issue

Posted: Mon Mar 04, 2019 7:24 pm
by Phlowen
Try replacing the effects loop's 12AT7 tube. Not sure what you're describing is a tube issue, but you'll find out REAL quick if it isn't. (See tube layout below)

Also, just for my curiosity, what cables do you have that aren't "metal ended"?


Image

Re: TH30 Effects Loop Ground Issue

Posted: Tue Mar 05, 2019 3:11 am
by chrisliua
Started with a tube replacement. No improvement.

And I have cables like these with the plastic elbow: https://media.guitarcenter.com/is/image ... 00x500.jpg

And these with metal elbow: http://www.long-mcquade.com/files/90419 ... 504739.jpg

Re: TH30 Effects Loop Ground Issue

Posted: Tue Mar 05, 2019 4:29 am
by Phlowen
Ah, I understand what you were talking about with the cables now.

It sounds like it's time to open'er up. Check all the solder points of the tube socket while you're in there.