Vintage Gibson PA, GPA 100HD...

[jozluck]

Allright, they sent me a schematic, no parts list so doesn't do any good... It worked fine when I recived it, all new sprague caps, etc.. was reworked.  Then it started haveing problems when switched on.. 1.It has a three way on-off-on switch- the schematic does not show if it has an internal breaker.  2.  The two main capacitors- one checks out, the other shorts out...but I have no part number and you try calling Gibson and see what they say...LOL! "We don't make them any more..."   Anyone know what the cap and switch are and where to purchase them... I'd replace both large caps....I don't see a number on the liners.... Thank you....

[Enzo]

Please post or link us to the schematic.

Interior photo would be nice.

Please tell us what the problem is so we know what you are trying to fix.

Does the amp turn on, regardless of how poorly it works, when you turn the power switch on?   In other words, does the power switch do ANYTHING like turn a light on and off?  If it does, then the switch works and internal main breakers are not blown.

2.  Two main capacitors?  That leads me to think this is a solid state amp?  What do you mean "shorts out"?   Goes to zero ohms and thus blows fuses?   Or are you saying it is intermittent?  Or what?

I don't recall ever seeing a cap with nothing printed on it, in fact just about all parts have identifying marks either in color code or a printed value.  For example 2200u or 2200uf 50v would be 2200 microfarad at 50 volts.  If one cap is good and the other bad, read the value off the good one.

If the unit is dead, you can do continuity checks with your ohm meter on the mains side wiring.  Is ther continuity from the mains plug to the transformer primary wires, and is there continuity through that primary?