Mark IV Reverb Problem - Help!

[mdortona]

I just picked up a used Mark IV - 2002 vintage. I'm having problems with the reverb --> sometimes it's on 100% working while other times, nothing. Here's what I have tried:

- plugged/unplugged & jiggled the connecting jacks
- removed and unwrapped the tank, visually checked the
connections/solder joints
- checked the rear pot (all connected)
- made sure all the tubes were fully in/seated properly
- made sure that all tubes were lit.

All other functions work fine.

Does this sound familiar to anyone? What should I do next? Time to take it to the shop? FWIW, I was thinking about doing a full retube, but before I do this, I would like to fix this problem first (unless there is a connection between it and retubing).

Thanks to everyone for their help! :?:

 

[lento]

Have you swapped the valves positions ?

Try swapping v3 and v4 (to and from the reverb) with say v2 and v5, to rule out any valve problem.

I had big problems with reverb hum on my Mk IV, tried all you've done and more.
Finally nailed it down to the fan of all things !
When I unplugged it, the hum stopped - figure that one out !

Good luck

Lyn

 

[mdortona]

Thanks Lyn! I'll give it a shot and post the results.

Matt

 

[mdortona]

No luck Lyn. Swapped the tubes no difference, although unplugging the fan got rid of the hum and extraneous noise. Back to the drawing board. :x

 

[lento]

Well Matt, the only other thing that was suggested by a tech, here in the UK was, it could be capacitor related. My IV B is a '95 model.

But, with your amp only being 5 years old, I wouldn't have thought so.

Lyn

 

[mdortona]

Looks off it goes to the shop this week. I appreciate your trying Lyn! Take care!

Matt