Gretsch Broadkaster Maxi-Lead 2x12 - Help

[dz123]

Hello!  I'm hoping somebody might me able to shed some light on & share some technical info about the Gretsch Broadkaster Maxi-Lead 60 2x12 S.S. guitar combo amp.  I "Think" it's from the 70s.

About 4 years ago I noticed a significant drop in the volume output.  I took it to a local repair guy who replaced some transistors & something else (I forget) and the amp worked like a charm for about 40 minutes and then the drop in output returned.  Unfortunately since neither I nor the repair guy could find any schematics or service guide the amp has just been sitting around doing nothing.

This is not my actual amp but maybe this pic of that I found on-line will be helpful Gretsch Broadkaster Amp

Maybe someone here has some experience w/ this amp or (fingers crossed) some documentation on it.  Any info will help.