Beomaster 5500

[Colliman]

Hi there, this is my first post in this forum.

I have a service question.

The receiver Bomaster 5500, do not react on IR controller or buttons on the receiver.

When I connect it, the "NO TIMER" and "TAPE" plus an J in the display.
I have measured all voltage around the IC´s, and I got the relay to switch on.

Does anyone get a clue where I can get some help, where to look next.

I try to upload the schematic, but this is more a question to someone how had experience with Bo.

[R_J]

One thing to check would be the 3V backup battery listed on page 3 as G1 if it is bad, it my effect the operation, if it is dead it acts like a short and can affect the reset, try removing it and see if it starts to work.
After that check all the supply voltages especially the +5V

[Colliman]

Hi R_J Thanks for the reply.
Checked that one.
3.2 V.

I think it's the CPU that's freaking out.
Have to check the ALE pin for a steady 1MHz.

Had hope the "J" reading on the display was a fault code.
But it's probably the CPU that give some static display not working.

And I had hope for an easy repair.

[CapLeaker]

As R_J already mentioned: check your power supply rails and that all the IC's around and including the main IC is getting fed proper power. After that, I would check some data pins between the main IC and the RAM, ROM and the address latch, looking for activity on the oscilloscope. I think the crystal oscillator is running, otherwise you wouldn't get anything at all.

[Colliman]

Thank’s CapLeaker for the tips.

Checked all power rails, but will do it again.
Thanks for the tip about the crystal.
Hopefully it's not the display driver that faulty giving the light.

[Colliman]

Found out the IC 1 8031 was the problem, waiting for a used one to replace.
Hopefully that will the only fault left.

But you never know.....

[CapLeaker]

Found out the IC 1 8031 was the problem, waiting for a used one to replace.
Hopefully that will the only fault left.

But you never know.....

Was it getting a bit warm?

[Colliman]

Was it getting a bit warm?

No, but I never checked that seriously.

Can check that before changing.

[Colliman]

Got 2 used 8031 from a friend for a bargain.
Also got a 40 pin socket, so I can change quickly.

Have de-solder the IC and solder the socket.

Enough for to day.

[Colliman]

After changing the 8031 I still have same indication on the display. So next on the list is M 5450 display driver.

[Colliman]

Contacted a friend that repair B&O.
He said there are used to be two frequent problems.
Bad soldering in some of the 600 solder points, a nice job to conquer.
Or the ROM.

So I will meet him, and test my cards using the new ROM.

Hopefully that will be the problem.