C audio RA3000 inProtection

[yvobtv]

hello there,
i've got an RA3000 amp witch of channel B has an issue.
a DC issue....
there's -8,7 volts on the output. (before the protection relais)
is there a schematic document to find?
thnx yvo (Dutch)

[PhaseLockLoopy]

Yo
I have one of these in my Garage for spares

It's the ubiquitious old chestnut Hitachi original design - long tail pair to a very basic bias into Gate resistors into FETs strapped across one of the most inefficient heatsink designs I have seen in decades.

I'll see if I can find diagram in service manual set - scan it in and PDF it for you... that is if I have one ...But the circuit isnt much different to HH VX1100 or a Citronic PPX900 (except without the army of fuses) --apart from facial and a few circuit differences, they 're all pretty much the same animal.

[AudioSystemsEng]

"Hitachi original design" - i beg to differ. Your description matches the schematic on the hitachi data sheet circa late 80's. But the RA- series amps are a little better than this.
i originally saw this design in elektor at a similar time. The main difference is that the drive circuit runs from a (10V) higher DC rail set than the output devices. I honestly can't remember any other details, but if you're not used to this design, please be aware that the +/- 90V rails will be active in the channel even if the channel fuses are not present.
This design also appears in those horrible studiomaster '1000' amps.