gretsch nashville 7154

[shovelheadsixsix]

I have a 1968 gretsch nashville soild state amp .When I use the built in  echo or the tremolo effect the amp will thump continuously without strumming a note.What is wrong.

[J M Fahey]

Grounding problem. Usually "mechanical" meaning rusty/worn/corroded contacts (do your PCBs use some kind of connectors, or crimped connections?) or maybe some loose nut in the grounding screw.
I think you get what I am pointing at.
Might also be old/dry filter capacitors. Statistically, these are the most likely culprits.
Third in the list might be old/rusty/dirty pots , jacks, etc.

[shovelheadsixsix]

Thanks. A ground problem was my first guess.I just got amp it still has a 2 prong plug  a ground plug is going to be one of my first fixes.Hard to find any info on this amp.any one have schematics?

[shovelheadsixsix]

repalaced caps today and still have the hum.now I will  try and figure out the ground problem.