Mark V intermittent power and lights loss

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Markyman

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Hi folks

Newbie on here from Old Blighty.

Apologies in advance if this topic has already been covered and put to bed; I did look, for ages, and found a few posts that were close but not exactly matching my issue.

My V is a 2013 model and I have owned it since new (Combo in hardwood). It has been fine for years, then over the last few months, it would ‘click’ and sound like someone had power cycled it. The fan would stop (for less than a second) and start up again, then everything returned to normal. This was regardless of what channel I was playing through.

A week or so ago, it clicked and then didn’t start up again. Panic! Observations: no panel lights on, but power tubes all glowing as normal, slight hiss from the speaker. Switching channels made no difference.

I checked every valve (sorry, tube) and they all passed as fine (Orange VT-100 and Senicore tester). I have checked the tubes twice now with the same result. The only minor niggle was one of the 6L6s had a tiny bit less gain than the other three.

I popped the chassis out and looked for any smoke in there, everything was normal looking. Tapping all the components with a wooden chopstick revealed nothing.

Then after three days of head scratching, it suddenly started working again! No dropouts, until of course I thought it was ‘cured’ after spraying contact cleaner everywhere and put it all back together, only to have it cut out again as before. Gutted.

So, I’m really hoping that one of you experienced Mesa men can suggest what might be the cause. I seem to remember the effects loop stopped working before the final death throes.

I don’t know if we have any Mesa techs in the South of England either; still asking everyone I can think of.

I have built a Cage amp from a kit and that still works beautifully, so I am not too clumsy with a soldering iron, but I think I may have met my match with this amp. :|
 
Weird indeed...

Have you tried different receptacles and circuits in the house?
At the rehearsal studio, I found an outlet that would make my amp just cut out until I re-seated the plug. It turned out to be loose wiring.
 
I had this issue and unfortunately it needed a power section fix from a tech. I would call Mesa first and see what they can offer as help.
 
Thanks guys. Some really good info here.

I have tried different power outlets (always start with the easiest solution), made no difference.

I think my next port of call is swapping out each preamp valve in turn. The trouble is, it can take quite some time for the problem to manifest itself.

From what I have read, I could still have a faulty valve, even though it tests OK in the tester; I guess it need to be fully heated up (not just for half a minute or so) for the components to expand and wobble out.

If I knew for sure which components were flaking out, I would be happy replacing these myself. I am just reluctant to yank any of the boards out without knowing for sure.

I will keep looking for a local reliable amp tech in the mean time.
 
The same thing happened to my amp. Here's my thread on it: https://forum.grailtone.com/viewtopic.php?f=33&t=84989

If you have a good tech in your area, bring it to them. They can get the tech info for the repair from Mesa.

It's a quick fix. A few diodes in the LV power supply need to be replaced.

It seems to be a common fault with the Mark V.
 
Maybe a bit late to help but just to chime in, I would agree diodes in power supply. Try Essex Amp Repairs in Witham, great service and great guys rescued my Mayk V from the brink after I had a woopsie with it! Any news on how it is Markyman?
 
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