Mark V Combo Reverb Not Working

[abe]

Hi Everyone,

As stated in the title, the reverb on my combo is not working. I rarely even use it, so I don't know how long it has been non functional. If I move the amp, I hear the springs pinging, but I don't get any reverb when I turn it on. Here is what I did to troubleshoot:

+ Checked to make sure that the connections were secure
+ Replaced V4 with a brand new tube
+ Ran the amp without the footswitch
+ Turned up both the channel master and the main volume
+ Tried all three channels in different modes
+ Turned off the effects loop. I heard a little bit of reverb when I did this, but I don't know if it was just pinging due to the volume increase.
+ Made sure that the reverb knobs were turned all the way up and went through the whole range (anyone else ever get it wrong because you are turn the knob the wrong way?)

I have no pedals out front right now.

What am I missing here? I tried to cover all of the troubleshooting before asking a question!

 

[jb's 52]

Did you try switching the input and output on the reverb tank itself?
Maybe they were inserted backwards. I've done this after cleaning.

 

[kreatorkills]

It happened to mine a couple years ago. Sounds like you went thru all the checks Mesa would have you do. Had to take mine to an authorized repair guy (under warranty) to have a diode or something, i can't remember, replaced. Supposedly a semi common problem with the Mark V. I waited why he repaired it, took about an hour.

 

[abe]

I didn't try switching the wires because I have never taken it apart, but good suggestion.

I guess it's going to the shop. I can live without reverb, but I can't live without every feature on the amp not working as it should, especially for those rare times, like the other day when I intentionally fired up the amp to play clean with reverb.

 

[bandit2013]

There may be damage to one of the J175 FETS in the reverb circuit. I believe there are three of them for each channel and one for the footswitch on the input of the reverb circuit. I had one short out and the reverb would not work. Best to have it service by tech as it is not easy to replace them due to limited space between components.

 

[bandit2013]

Before you ship your amp out for repair, or end up replacing tubes (which may be the culprit). check the cable connections. Also if you cycle the rotary channel selector on the back of the amp that may help unconfused the logic controller. You can unplug the footswitch. Reverb circuit will default to on when foot switch is unplugged.

Check the reverb wires, on the amp, white is facing back of amp, black or dark grey is towards front. If you got them backwards, the amp will squeal or sound really terrible. Keep it simple before thinking the tech service required. If all else fails and you cannot remedy the problem with hook up cables or preamp tube, reverb effect level setting on the back panel, or cycling the logic controller. If all else does not fix it, send in for repair.