Beocenter 7000 Power up fault

2 replies
M(
Malcolmatkin (archived2)
Bronze
2 posts
Posted April 8, 2020 at 22:03 GMT
#2136523

New to this forum so bear with me!

I have a Beocenter 7000 that fails to power up correctly. All I get is the 2 Standby LED's and nothing else.  I have all the correct voltages on PC3.  Following the service manual troubleshooting guide indicates that the microprocessor board (PC21) should be replaced. 

There is a microprocessor board from a 5000 available on eBay. It is very similar and looks like the only difference is an extra chip on mine which I'm guessing runs the remote (which is long gone.)

So does anyone out there recognise this fault and able to comment please!!!

Many thanks

Malcolm

SO
solderon29
Gold
1051 posts
Posted April 9, 2020 at 09:09 GMT
#2136524

The fact that you have two "standby" indicator lights working suggests that the upc is running,but it may be running amock?

Check that you have a 50 or 60 hz(depending upon whereabouts in the world you are?)pulse at IC5 pin 39(4.6v),and also check the reset capacitor C34.

The '5000 and '7000 control pcbs are quite different,and the chips are not interchangeable.

You'll notice that the upc and it's expander chip are mounted in sockets.Both the ic pins and the socket connectors can become oxidised.It's worth gently removing the chips and cleaning the pins.Handle appropriately observing static precautions.

Check also on the controller pcb for dry soldered joints where the wiring loom connectors are fitted to the pcb.

The set also has a safety protection system,which will prevent switch on if certain faults are present.

If you are not sure of the back story of this unit,it might be worth checking that the main amplifier output transistors etc haven't failed?

Nick

 

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