Mesa Boogie SOB limiter control

[lowell]

Hello,
working on a Son of Boogie. The limiter control is quite scratchy when adjusted throughout the 1-3 range on the knob. I've replaced the constant current source diode, both phase inverter coupling caps (thought it might be leaking DC), did a full filter cap job (caps are 20 yrs old), and replaced the pot itself as well as the tubes. The owner replaced the pot before I did which didn't fix it. Anyone guess what's up w/ this thang?? Could it be that the original pot was a rheostat and the pot in there now can't handle the voltage?

Thanks!

[stokes]

I would guess that the pot should be a rheostat.Regular volume type pots dont like dc voltage.Thats why pots connected to leaky coupling caps get "scratchy".Dont think its a matter of the pot"cant handle the voltage",they just dont like any dc voltage at all.The coupling caps between the PI and power tubes wouldnt affect the limiter.Where did you find that TCR 508 diode?I've been looking for one with no luck.

[lowell]

Hey,
Yeah I couldn't find 'em either... however was lucky enough that this customer is endorsed so they asked Mesa to send a few.

Lowell