Has anyone ever added reverb to a Mark III?

[bounder]

Was wondering if anyone has ever tackled the project of adding reverb to a Mark III that came without that option?

 

[Restless Rocks]

Yes! Given that the circuit board and chassis is fully set up to accept the components it's only a simple matter of installing a tube socket, transformer, two rca jacks and just a few resistors and caps. And of course mounting the pan. If you have a head shell the hardest part of the whole process is cutting out the bottom of the cabinet to mount the pan. In a combo a couple screws to intall the reverb pan "bag" is all there is to it.

 

[bounder]

Great, I just emailed Mesa to get a price quote for all the parts.....I was hoping the circuit board would be the same, didn't figure they'd build several different boards. The amp is on it's way to me in a UPS truck, I bought it rack mounted & I'm installing it into a combo cabinet with a Celestion G12T-100 for now while I look around for an original Black Shadow. I have electronics experience, so it should be no problem. I don't think this amp has had any of the mods done either. Am I correct in thinking there are 3 mods? The R2 mod with the 250K pot in place of R130, the reverb mod where you solder a 3.3k resistor inline with the effects return & there's one I can't find info on (C1 mod to boost lead channel????)
Thanks for the help

 

[Restless Rocks]

A lot of guys who rack mount the heads just don't bother to fit the reverb tank so you may already have the onboard components. The 3K3 resistor in series with FX send is a must. Also you'll need to use a 2watt 33k resistor for the driver transformer primary/plate load on V4A. You may want to search the R2 master mod as there are actually a couple different ways to go about it one of which will affect the reverb level when in R2. This topic has been well documented and there are several pics available if you hunt them down.

 

[jonarobb]

Mark III Board w/o Reverb

Mark III Board w/Reverb

Easy as pie to add verb to this amp. Besides populating the board around V4, and adding the usual suspects, tank, tranny, pot, RCA jacks, etc...., you'll have to lift the board to get that new tube socket in place.

 

[Restless Rocks]

I've been able to install the V4 socket by releasing the board stand-offs on that side of the board and merely lifting it just enough to ease the socket underneath without any desoldering or other hassels.

 

[jonarobb]

I've been able to install the V4 socket by releasing the board stand-offs on that side of the board and merely lifting it just enough to ease the socket underneath without any desoldering or other hassels.

agreed. i meant the board would have to be lifted as oppossed to getting the socket in any other way. i like to free the board from all the standoffs as to not put any strain on the traces. shouldn't have to un-solder anything in any case.

 

[bounder]

Great, Thanks for all the info. I should be getting the amp Wednesday, so I'm sure I'll have a much better idea of what I need to do once I get the amp in front of me. I'm sure I'll have more questions. I know it never had reverb, the pot mounting hole next to the presence control is plugged. I wasn't aware there were different ways to do the R2 mod. I thought you clipped the one end of R130 & soldered one wire to the board & soldered the other wire to R131, then installed the pot to the other ends of the wires, one to the center lug & one to one of the outer lugs. I'll have to check that out more.

 

[bounder]

OK, so I've been tracing the circuit around V4 and can't find where the reverb input and output come from. Do I need to wire the reverb output into the tip of the effects send jack and the input of the reverb circuit to the lead master pot. If I need to wire those as I think, do I need to install the 330K resistor shown in the schematic above the effects send jack? If so where does it go?
Thanks,
Bruce

 

[bounder]

It's done & works great! Thanks to the help of a few great guys on here & of course a little guidance from Mike B. All in all, it went together pretty easily. Thanks for all the great advise & assistance!
Bruce

 

[jonarobb]