MarkIV volume drop

[Tyrant]

Help! This MarkIV rev.A has an issue.

After about 20 min. of playing the volume drops to really low level. Once it drops it will sometimes waver up and down in volume and it will most of the time eventually come back to normal volume. I've searched the forum for quite a while and found a few topics. I'll be damned if I can figure it out. I have cleaned and tightened the tube sockets. The amp has all new tubes. And multiple swaps with known good ones. This most recent time when the volume dropped I went to look at the back of the amp and accidentally bumped the ground switch to the b position and the volume instantly came back up to what seemed to be the original level. Come to think of it, if memory serves it's only happened while in R2 but then again I spend alot of time in R1 and R2.

Electrons aren't my friend but I'm a quick learner. I have a show this Saturday and I was hoping someone could help. From what I've gathered it could be a tube issue, groundstrap, bad pot or possibly in need of new caps. The master volume pot and the R2 presence pot have a little play in them but appear to work normally. I'd hate to have to take it to a tech. Any comments would be appreciated.

Thanks

 

[chris_EIT]

I have had this issue occur twice... weird enough i tap the side of the amp and it fixed itself... scared the hell outta me when it happened. just make sure you check all your cabling to make sure its not a ruined cable issue. I know that can happen. Busted speaker lead etc and what not. But im sorry i can only tell u that much
What year Mark IV is it?
Mine's a 90 or something so I probly should get it cleaned up anyways

 

[Tyrant]

It's a '94. I'll check the wiring again. thanks!

 

[chris_EIT]

I spose it could be a number of lose components also, being the age and all. When the volume goes down does it just randomly go back up?
That's what happened with mine

 

[Tyrant]

The volume goes back up but takes over a minute. I've only let it do this a few times, kinda paranoid about frying it completely. If I put it into standby and back on it seems to run perfect after that. I was hoping to get it sorted out but it looks like I'll be dropping it off at the tech and use the Nomad. Thanks for the input.

 

[Tyrant]

Would anyone be able to recommend a tech in the Portland, OR area or have any experience with Inner Sound?

 

[Tyrant]

Well the amp is back from the shop and the tech said it checked out fine except for the volume pot, which they replaced. They could not get the amp to fail at the shop. I got it home and fired it up, withing 5 minutes the volume was cutting out to low levels again. I stumbled upon a post here about cleaning the effects loop jacks as they can get dirty or out of spec and cause trouble so I cleaned all jacks. Not sure if that made the difference but during rehearsal the amp performed perfectly with the master at 5 for 6 hours. Zero volume loss. On to the show, 2 hours and the thing didn't even break a sweat.

I just thought I would throw this out there in case anyone else has a similiar issue. Also, if I'm getting low amps, volts or dirty power at my house is it possible that it would cause the Mark's volume to drop so dramatically? I'd prefer not to run out and buy 400 dollar regulator. I do however have the multimeter ready to go if it cuts out again.

 

[chris_EIT]

Well dude, this is VERY helpful, when I knocked my amp to fix it maybe it move the effect loop jack running out of it, now that I think bout it, one time it dropped volume I twisted the loop out and VOILA! Works again...
Interesting!!!

 

[Tyrant]

I just used deoxit on the lead and put it in and out a few times. With any luck at all it will hold up.

 

[flip33]

My Mark III started cutting out last week. A wave of horror swept through my body... so I began looking for problems. I jiggled the effects cables and it went away.

I will clean the effects loop jacks.

Thanks for helping verify this problem so I can solve it.

 

[NickSleeper]

Ive been having this same problem, although I cleaned all the jacks and checked everything - I even did the tapping on the amp XD
Still no results -
So I just shipped it out to a mesa certified repair station. If it breaks 200 on a repair im going to buy a Peavey Bandit.