Crown DC300A

[Jerry]

I'm looking at a Crown DC300A that has a problem w. channel 2. With no load it puts out a nice sine wave on the scope. With an 8 ohm dummy load the top half of the waveform is clipped. Would anyone(Enzo?) have a schematic of this amp? It has the IOC circuit. Thanks in advance for everyone who helps out here!

[Enzo]

Yes I do, but really, call Crown. They can send you a nice copy. I'd have to scan several large fold-out pages in multi-scans.

If the output is clean but collapses under load, I first suspect a bad driver or open output device, or open ballast resistor.

[Jerry]

Looking on Crown's website I found the operation manual for the amp. There was no schematic, but there was a layout of the driver board and the input board. There were also part lists, so that helped out some. I pulled the output xstrs and tested them with a Sencore Supercricket. They all test good ,but half of them are considerably lower in gain. I put 2 back in the circuit(similar gain) and fired it up. No IOC light and a full sine wave. With the age of all the transistors I'd probably change them all out if it were my amp,but it's not. ?

[Enzo]

I am surprised the schemo is not in the operating manual. All the manuals I got with my old Crown stuff included them.

But the advice was to call Crown and ask for the drawings. Not look online. Usually they are quite helpful.

[Jerry]

Well,I ended up replacing the output xstrs on the one side and the amp is working great.