Using amp in receiver

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I have a Denon AVR-5800 receiver that is about 20 years old. It stopped working so I took it in for service and they told me a digital board was blown and the part is no longer available so they could not fix it.

I hate to throw it away because it has a really impressive amp for a receiver. The thing weighs about 50 pounds and the amp does 170 watts/Ch.

It has external preamp inputs so I am wondering if it is feasible to rewire it internally to go from the external preamp inputs directly into the amp section of the receiver and drive it from an external preamp, bypassing everything else in the receiver.

Unfortunately I don't have the experience to do this myself but I believe schematics are available on line.

Has anyone else ever done anything like this?
 
> the service manual doesn't have schematic

That one is missing 15 pages. There's better docs here:
Denon AVR-5800 - Manual - Audio Video Surround Receiver - HiFi Engine

You have to find connectors CX076 and similar, one per channel, on the Power Amp board. The connector has the signal input, also mutes (which may be ignored), and frontend power (which must be retained!) Signal and ground are pins 4 and 3. It could be easier to leave the connector and lift one end of R101 R102 etc, shove signal in there, tap ground near connector.

The inputs are a very reasonable level: 2V peak for FULL output (probably less for steady tone). Input impedance is about 12k, which any transistor source will drive. Removing R?01 makes it over 50k, which many tube preamps will drive.
 

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You guys are awesome. It will be a couple of weeks before I can pick up the receiver from the repair shop and a while after that until I can tear into the unit. I am sure I will need more advice so I'll be back eventually.
 
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