lead return mod on mark iii head

[treehorn]

Is anyone aware of a mod for a lead return on a mark iii? I have a mark iii that has an extra jack with "lead return" taped next to it. Another label, "rhythm return", has been taped next to the usual effects return jack.

I'm not entirely sure how it's intended to be used... there's only one effects "send". Would I put a Y on the effects send, route them through separate lead and rhythm effects chains, and back to the two return jacks?

 

[Restless Rocks]

When you have the chassis out for your pot repair perhaps you could share some clear photos of the innerds and we may be able to tell you more.

 

[treehorn]

Ok... I posted some photos on picasa. Hopefully this link will work:


http://picasaweb.google.com/112841688694453981440/MesaBoogieRepair?feat=directlink

The mod looks fairly sloppy. I've experimented with putting an effect between "send" and "return", which affects all channels, and between "send" and "lead return", which only affects the lead channel. It's unclear to me whether both returns could be used at the same time, or how.

I didn't have time to trace the whole circuit. Perhaps another time.

Any thoughts?

 

[MrMarkIII]

Effect send level for R1 is determined by Volume, while send level for Lead is determined by the Lead Master. Maybe those two Return jacks are padded up or down to compensate for wildly different user send levels. You can only use one at a time, which doesn't sound too convenient. :lol:
Unless maybe an A/B switch?

 

[Boogiebabies]

Effect send level for R1 is determined by Volume, while send level for Lead is determined by the Lead Master. Maybe those two Return jacks are padded up or down to compensate for wildly different user send levels.

That's exactly what it looks like. I would say it's an old Mike Bendinelli mod. The LDR's are from 1987.
Considering our racks back then, it would not be too difficult to imagine multiple effects units.

Call Mike.