Sovtek Mig 100 U speaker output issues

[g1]

Do you still get the loud hum with no cord in the input jack? Louder than with guitar volume down?
If so, the input jack switch is probably not closing when the cord is removed.

[Jesse Pearson]

Hi G1, I was thinking the same thing and maybe the guitar cord was acting up? Thanks

[Enzo]

A shorting plug is a good thing to keep in your kit. This would be just one place it is useful. I also keep a TRS plug with tip shorted to ring in my kit. it bridges insert jacks.

[Jesse Pearson]

Thanks for the heads up Enzo, I'll add that to my own kit and research it's different applications to add to my knowledge base. Well, I threw out a cord that couldn't be repaired that was being used on the day in question and I also realized that my "One Spot' power supply for my stomp boxes was right next to the power plug to the amp. I think this contributed to the high EMI that day in the amp when nothing was plugged into the high gain jack.

[g1]

At the top of the page in the "maintenance & troubleshooting section", there is a sticky post titled "the dreaded switching jack problem", definitely worth a read. It has very good info on the issues that these type of jacks develop. As well as being used for signal routing, they are often also used to short the input to ground when not in use. This helps keep noise down when you are not plugged in.
The shorting plugs Enzo mentioned can help find such faults.

[Jesse Pearson]

Thanks for the heads up G1, reading "the dreaded switching jack problem" now. Wow, duh...I had no idea there was a Trouble shooting, repair section to the Sunn Forum. I've been posting in the electronics section...should this thread be moved to the "trouble shooting , repair section? I guess that's where I should be posting trouble shooting and repair stuff in the future, is that a correct assumption? Man, so much cool stuff to read and learn.