The capacitors on the power supply module 16 will probably be bad. The reset circuit for the CPU will need checking, if my memory serves me rigth there's a trimmer that goes bad. Finally a complete overhaul of the amplifier module, new caps and new trimmers for idle current and DC offset (plus of course a new adjustment of these) Burned resistors should be investigated further. Check also for cracked solders on module 14, it's very common to see, especially at the connectors.

The Beomaster won't power up if the amplifier is at fault (for safety reasons) but it should come into standby (one red dot) with mains connected.

Martin

Hi

Check that you have all the voltages on module 16. On my unit the 6.5v was out of spec and it's controlled by the trimmer R4. Also check the uC-supply on module 6 - it will feed the microcontroller with 5v at pin 40 (ic4 on mod 2). This auxillary supply is fed from the 15v of mod16. You will not get any 5v p-p on collector of tr4 mod16 if the microcontroller doesn't have 5v.

/Fredrik

Hi,

Thanks Fredrik for these advises, I will check them tomorrow, but now the µC works fine thanks to Martin.

Thanks Martin, now I can switch on or off the beomaster, I can adjust the hour...But the LED display in FM tuning mode only show 74.8 and when I change the frequency, it doesn't modify the display.

Then , I will check the amp module but what are the value of idle currents (10mA like on a beocenter 7000 or more...). 

Thanks again for your help Martin and Fredrik!

Regards,

Mathieu

The factory specs are all stated in the service manual which also gives the correct measuring points. Replace the trimmers before adjusting, the old ones will be bad and could be the reason for the Beomaster not working. There are four trimmers in total on the amp board.

The 74.8 FM readout is the typical symptom of a dead prescaler IC. This part has been obsolete for years but I still have a few in stock, not the cheapest IC though but of course worth it if you get the rest of the Beomaster going.

Martin

Hi Mathieu 

Nice work - it's starting to wake up 🙂

I'm curious of what had happened to the output amplifier. Please tell me when you find out. Maybe some photos of the damage?

/Fredrik

The idle current of the output amplifier is 50mA or 22mV across the resistors R143,R144 (Rch) and R243,244 (Lch)

/Fredrik

Hi,

 Thanks Fredrik for this information, I will check the amp module in few minutes and I think it was a problem of overloading... I have also some pictures of it, but I don't know how I can add them?

I have checked UC264B and I have a DC signal at its input and not an AC one. So it could be the cause of the 74.8 FM readout on the LED display.

Regards,

Mathieu

Hi

To attach a picture - select reply, on top of "the old message" select the options tag and select Add/Update. There is a limit of file size at 100kB.

/Fredrik

Martin, do you supply a full overhaul kit for the Beomaster 6000.

Mine is working ok, or it was last time I tried it, but I'd like to replace all the electrolytics, tants and anything else that should be done.

I also rember you said something about adding a heatsink to the display driver or was it the fm decoder chip.