[Martin Lundholm]

Since nobody objected, I put board 9 from the BM6500 in the BM5500, and this combo works fine 🙂 So that’s a relief at least.  Also the CPU boards (4) looks exactly identical so I will try switching in the one from BM6500 next. The SW may be a bit different, but switching between inputs should be the same.

[Martin Lundholm]

Thank you for your suggestion! But I have already a project plan for a long winter (or two) which is to replace the Mostek 3870 CPU in a BM6000 with an atmega-1284p 😊

[Martin Lundholm]

I put the BM6500 on hold for a while, but yesterday I started to troubleshoot it again. It’s not a lot of transistors in the IR receiver and I tried to replace a few. But with no positive result. When testing the BF240 I got an extra diode in the test screen which I haven’t seen before (see the attached file). I think the transistor is fine, as the other BF240 showed an identical image. I put them back as they seemed fine. Anyone who knows what the extra diode means?

I’m not even sure where the 100Hz is I see on the final IR input signal coming from. The only LC-circuit I see is the IR receiver and that sure (I think at least) doesn’t produce 100Hz.

Anyhow, I have a working BM5500. By looking at the schematics I could try to replace the front PCB with the one from BM5500. Actually the schematics for the 5500 and the 6500 are confusingly identical. I got even unsure if I actually had the right schematics, but it seems so. If I can replace the PCB, I can also check the signal from start to end and compare. That should give me a clue of what is wrong, or if it’s actually something else.

Does anyone know for certain if the IR receiver/transceiver boards are identical for the BM5500 and the BM6500? I wouldn’t like to end up with two broken Beomasters…

 

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[Martin Lundholm]

I kept power down and up with 30-60s in power down, and eventually it responded to the remotes! The idle square wave actually looks a bit different now. It’s  ~50 Hz and the duty cycle looks rather different from the two previous photos and is more steady. So I guess I have to investigate what is driving the idle square wave. I have had a glance at the circuit of course, but there are mainly BCnnn transistors which rarely fails from my experience. But it would be a rather quick thing to change them, if I have them at home. Well, there’s a BF240 and I don’t have any BFnnn transistors. Will check if I can replace it.

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[Martin Lundholm]

Thank you for your reply! No, unfortunately it didn’t help. I can see the IR receiver signal in the oscilloscope, but the Beomaster is still cranky.

I have a Beomaster 5500 which responds to both the MCP and the BL1000 so I know the remotes are working. Well, I had to replace to opto sensor in the MCP to be able to control the volume…

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