Mesa mark V 90 combo. Quick and easy post.

[nandrewjackson]

Hello all. I haven't been building anything for a couple years but I've done a couple repairs lately.


The amp for this post is a mesa mark V 90 watt combo.


I bought it for myself, used. It's a fairly early serial  number for the model.


Apparently there can be an issue with some diodes in the amp that may cause switching issues when the footswitch is connected. But, I don't have the footswitch so I don't know if this one needs that particular repair. I have a footswitch on order.


Anyway, that's not what this post is about.


I didn't immediately pull the chassis after the purchase. I played it for about a month before doing that. It's a pretty cool amp. Tons of bells and whistles. I thought it was nice without ever pulling the chassis. But, some of the bells and whistles didn't seem to make any audible change. Specifically, the "bold/normal" switch for channel 1.


I pulled the chassis and looked over the circuit. Someone had obviously tried to "mod" the circuit. Lol.


I chased down the schematic online and found what seems to be a legitimate version.


There were 5 or 6 components in the audio path that had been obviously tampered with. Since pulling the board from the chassis is practically impossible, they had cut the old leads and either tied in the new components to the old component legs or tacked things on parallel.


I ordered some replacement parts and undid the "mods".


The particular feature that didn't do anything when I first got the amp now actually does what it should. Or, at least it does something close to whatever OEM should be. They had removed the cathode bypass cap for the first stage and changed the R value too.


The other mods that they did weren't too far from stock, but I changed them back anyway.


It's a really neat amp. It does clean, tweed, Plexi, and fire-breathing, all quite well.


I suppose I'll post about the footswitch whenever mesa makes more of them and ships them out.


Thanks everyone for the info about amps over the years.


Happy new year!
😎✝️☃️🎸🎸🎸🎸🎛️🎛️🎧🎸

[Latole]

Happy new year and enjoy your mesa B