Mark III Green Stripe reverb not working...?

[Beats]

Hi all!

I have a Mk 3 green stripe combo that i'm selling for a friend who's moved abroad. All seems well, other than the reverb - it doesn't seem to be on at all.

I've changed tube v4 (the leftmost tube when looking at the back) with the spare tube, but to no avail. I've tried using a Boss FS-5L footpedal/switch to turn on the reverb, both with a stereo and a mono jack cable, but, nothing. The reverb knob is turned up to 10. The grey cable appears to be plugged into the bottom of the amp just fine.

Any idea what else i could try, troubleshooting wise?

I assume the reverb tank is the thing that's wrapped up at the bottom of the cabinet, under the fan? I tried to take the back panel off with the 6 screws, but i couldn't get it completely detached - the fan is screwed to it and was giving me a hard time. I didn't want to break anything.

Anyway, any advice is appreciated!

Thanks!

Ed

 

[McBarry]

Get a multimeter, check the grey cable for continuity (not so likely)
While you're there, check the orientation ie one grey cable plug should have a red mark and one jack in the amp chassis should have a corresponding mark.
Then check the tank resistance at both jacks. Open/infiite resistance is suspicious.
If either jack is open, remove the tank and open it and check the tiny cables from the RCA jacks to to tiny transformers.
These cables are THIN and fragile, and are well known to fracture at the joint with the RCA jack. Often..
After that, I'd be looking inside, but only if you're comfy working around a live chassis.
Plenty nasties lurking there - send to a tech if yr not skilled at this.
Regs, DB