Trobuleshooting Silvertone Solidstate 150

[Ian MacGregor]

Hi,
The studio owner where I work just picked up a used Silvertone Solid State 150 guitar amp and matching 6x10 speaker cab (all Jensen :shock: ) at a studio sale. With a guitar connected to the amp's input, there is a very loud ground hum. The guitar can be heard below the hum at regular volumes, IOW it sounds fine except for the loud hum. The amp's power cable is only two prong. Any suggestions?? I'm just starting to get into teching amps (biased my JCM 800 for the first time tonight), so I figured I'd post here and see what's up.

Thanks!

Ian

 

[PRR]

The Jensens and the case are a real find.

A Solid-State SilverTone, though.... I may be wrong, but I don't think the world would cry if you just threw it in the dump.

But your boss bought it, and you want to learn fixing, and the SS-ST is a good sacrifice to your education.

Open it up.

Learn what is inside.

Look for "wrong" stuff: loose jacks, unplugged connectors, burnt parts, can-caps that are leaking guts.

Many of the bigger transistor amps had separate preamp and power amp boards. By unplugging a cable, you can operate the power amp without any preamp signal. It should be quiet: a little hum and hiss in the speaker, but silent a few feet away. If not, then you have probably isolated the problem to the power amp board.

Actually you can learn a lot from the outside. Which knobs affect the hum, which don't? If there is an insert or pre/power jack, what happens when you plug in there? When you power-off, does the hum quit instantly or fade down?