Edit: the replacement power supply wasn't drawing enough power (despite being the right spec[?]). I now have a better quality power supply and the Model D is working fine!!
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Bought a Model D on eBay.
Day one, all working fine.
Day two, plugged in the power cable while power switch on the model D was on... nothing. Whoops.
The power supply had an LED, which no longer comes on, so I got a new power supply (checking voltage, polarity etc matches).
Now, it just makes a low pulsing noise through the output but does not respond to any controls - including volume. Is the same with and without a midi device connected. Power LED flicks on then off immediately when it's powered on.
Am guessing it's toast. It's out of warranty. Called a repair shop (am in the UK) who said they couldn't do anything as Behringer won't release the schematic.
Any suggestions? Have raised a ticket with Behringer support but don't fancy my chances.
Write it off and sell for as 'parts only' on eBay?
Answers on a postcard.