Issue with Mesa rectoverb 50

grungebob

hello all, the gain channel on my Mesa rectoverb 50 combo doesn't seem to be switching between vintage and modern on the toggle switch, simple switch cleaner needed or something more sinister?
if I give it a good old wiggle it'll change but seems to revert back to modern within minutes 

ICBM

Could be the switch. Lie the amp on its back and squirt some Servisol into the front of the switch, and operate it a few times.

If it's not that it could be something in the switching it controls, rather than the switch itself - basically it turns the power stage negative feedback off (in modern mode) with an opto-coupler, so if the opto-coupler is failing it would do the same thing. This s a fairly common problem with the Mesas that use optos unfortunately...

grungebob

Ok thanks will give it a try appreciate the help 

grungebob

So would wd40 be ok?

ICBM

grungebob said:

So would wd40 be ok?

Probably not unless you've tried contact cleaner already and it hasn't fixed it.

grungebob

Doh it's all I currently have. Oh well maplin here I come. Thanks again @ICBM ;

grungebob

Hmm seems that the switch cleaning didn't work.  The part that you mentioned @ICBM is it worth the fix ie cheap enough to source and fix or live with it in modern mode?

ICBM

It's not a very expensive part, but it's not yet a certainty it's the cause unfortunately... there are other components in the switching circuit too. If it is the opto it's an easy fix, but you need the specific type - Westside Distribution will supply them.

Do you prefer Vintage or Modern? If you only use one you could either leave it (Modern) or bypass the opto (Vintage) - which is the easiest way to confirm it's the problem anyway.

Or you could even fit a variable control for it to give intermediate settings - I did that for a friend who found Vintage too tight and Modern too boomy.

grungebob

Ok thanks somethings to consider then. Just gave it another go and it seems to switch more often though sometimes the vintage sound comes when in the modern position. I have a use for both sounds so would like to try fixing it I think. I'm ok with a soldering iron and can follow large scale p&id for industrial sites so hopefully I could follow the schematic for this amp?

ICBM

It can't be the feedback LDR then - getting the Vintage sound in the Modern position wouldn't happen because Vintage requires the LDR to be on. Sounds like it's something else in the switching circuit. It *could* still be the front panel switch, especially if it's more intermittent.

Try jumpering the switch contacts inside and see if that makes it switch reliably.

If it's more complex than that I can send you the schematic.

grungebob

Ok thanks @ICBM appreciate you taking the time to respond. I'll try jumping  the contacts see what happens if not then yes please would love the schematic 

grungebob

Not had chance to check contacts gets but tired cleaning again which improved some more and then left the switch in the vintage position for several days. Now switches 6/10 times first go. Sounds like a contact issue to me?

ICBM

grungebob said:

Not had chance to check contacts gets but tired cleaning again which improved some more and then left the switch in the vintage position for several days. Now switches 6/10 times first go. Sounds like a contact issue to me?

Yes, I think so. Given that changing the switch is fairly straightforward if you can solder, I'd try that next.

grungebob

Thanks again. Fingers crossed!

grungebob

right holy thread Resurrection but......
not been able to play this amp for a while due to it being packed away for a house move, got it all unpacked and sounds great still but gain channel now stuck on modern and there's some hum to the amp on the clean channel, It might have been there before but i'm having to play the amp much quieter than before due to my daughter sleeping in the room below where its set up.

is the Hum normal for this amp ,will I ever be able to get the voicing switch replaced or do I just buy an amp more suitable to home use now I know i'll never gig again?

sorry to bother you @ICBM but care to comment re the issues?


Thanks 

ICBM

It should be easy to change the switch, they aren't PCB-mounted.

The hum is more of an issue if a filter cap is on the way out - it might be, especially if the amp has been in storage for a long time.

Whether to keep it or not is a decision for you... but bear in mind they haven't held their value, exactly because smaller amps are becoming more popular.

grungebob

Ok thanks, I'll see if I can get it looked at then.

Thanks again.

DJH83004

I have to say IC my money would be on the opto, I have actually had good results using the Vactrol VTL5C1 on Mesas in the past, they seem pretty reliable, just a bit of a pig to get to as always 

ICBM

DJH83004 said:

I have to say IC my money would be on the opto, I have actually had good results using the Vactrol VTL5C1 on Mesas in the past, they seem pretty reliable, just a bit of a pig to get to as always 

Mine would have been too, except that he says it was working about 6/10 times.