Crown DC300A Oscillating

[rf7]

I have a DC300A on the bench that one channel was folding the top half early into a load. I couldn't get the original 2N5804 driver transistors, so I used a pair of MJ21194 transistors as replacements. I adjusted the bias for that channel, and it has no DC on the output. Now the amp goes into a big oscillation as soon as it clips into a load. I added a 200pf compensation cap as C119, which is shown on the schematic, but that didn't help.

Do I need to pay big bucks for 2N5804's to make this work correctly?

Or should I replace all of the output devices with MJ21194's on that channel?

Or just try compensating caps elsewhere?

Service Manual

[Jazz P Bass]

The parts list shows different caps for C107/ 207, depending on the output transistor grade.
(Crown is big on graded outputs)

Certainly Not an easy amplifier.

I would contact Crown.
They have been most helpful to me in the past.

[Jazz P Bass]

Have you taken notice of this little ditty about C119/ C219?

DC-300A-C119_ C219.pdf

"Used Only If Oscillation Occurs During Test"

[rf7]

Have you taken notice of this little ditty about C119/ C219?

[ATTACH]47186[/ATTACH]

"Used Only If Oscillation Occurs During Test"

Yes, I specifically added that cap to stop the oscillation, but it did not help.

[rf7]

I replaced the MJ21194's with MJ15024's and that took care of it.