Crown DC300A

Jerry · 07-17-2007, 07:33 AM

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 · 07-17-2007, 10:37 AM

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 · 07-19-2007, 01:27 AM

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 · 07-19-2007, 01:35 AM

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 · 10-13-2007, 03:01 AM

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

07-17-2007, 07:33 AM	#1
Jerry Member Join Date: Apr 2007 Posts: 65	Crown DC300A 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!

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07-17-2007, 10:37 AM	#2
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,352	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.

07-19-2007, 01:27 AM	#3
Jerry Member Join Date: Apr 2007 Posts: 65	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. ?

07-19-2007, 01:35 AM	#4
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,352	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.

10-13-2007, 03:01 AM	#5
Jerry Member Join Date: Apr 2007 Posts: 65	Well,I ended up replacing the output xstrs on the one side and the amp is working great.

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