Denon A/V receiver AVR-1604 powers off

[dahbrown]

Hi. I have just purchased this unit from ebay.
When you turn it on, it powers up for about 3 seconds and then powers off again.

Any ideas where I can start looking?

Thanks

Dave

[jts1957]

Audio Output devices and power supply.

[dahbrown]

Thanks for that. What votage values and where should I start probing?

[dahbrown]

Found that 15v regulator is stuffed. Suspect that 15v rail on the analogue input stage is shorted. Just need to get a couple of spare 7915 regulators to prove...

[jts1957]

Something's backwards.
That would be minus 15 volt regulator (Or 7815 for positive 15 volts).

[dahbrown]

Sorry, my mistake! Yes it is the -ve 15v rail.

I replaced the 7915 and same thing occurs, powers on and then during POST it shuts down. I removed all input cards, which just leaves the main board, bridging board, CPU and front display.

How am I am able to isolate the fault, as I have checked the diodes on the CPU board which seams to have the -15v rail on it. But could it be the CPU or bridging board.

Thanks

[jts1957]

What is the voltage and resistance on the minus 15 volt line?

[dahbrown]

There is no voltage on the -15v rail. The resistance was around 400 ohms. Also discovered that the resistive fuses from pin 4 and pin 6 from the supply voltage (R141 and R142) were open circuit too. So replaced them and they blew once unit was powered on. In stand-by mode all is OK. Need to power up via remote control, during POST this is when the unit is turning off after 3-4 seconds.
Next plan is to short the power relay to isolate the bridging board and CPU board and determine that main board is OK?

[jts1957]

You could always jumper across the fusible resistors and "follow the smoke"

[Xtech]