"Eeyore" wrote in message
...


TimPerry wrote:

what fires the 2n5064 in the crowbar circuit? looks like the 2 gates
are
tied together and go nowhere else. how does that make a diac?

You know, I'd never looked at that in detail. That's puzzling.

maybe leakage at the p-n junction on one is enough to fire the gate on the
other under full DC conditions. just a wild guess.... or maybe the
schematics are just plain wrong. it's not uncommon, unfortunately. i don't
feel like tearing mine apart just for curiosity's sake.


I do indeed use a diac myself in that application. Look at the Behringer
EP2500
schematic, they copied it 'verbatim'.

Graham


any chance you have a QSC USA 850 schematic? a DJ blew mine up. i don't use
to anymore except as a loaner but im sentimentally attached to it.