[Glitch]

I haven’t made any real progress on the BM6000. I’ve resorted to replacing diodes and transistors that I didn’t think were bad. The removed parts tested OK. I’ve been able to slightly change how the circuit reacts, but it is just a different version of random behavior.

The good news is that I’ve been able to get my Beomaster 8000’s working. I have one fully working and a second that works except for the FM display. I have parts on order to fully restore/repair these.

My next step on the BM6000 project is to run some experiments on one of the BM8000’s to see if I can learn anything about how B&O handles the start-up procedure, especially when faults are detected. Ideally, I would run these tests on a working BM6000, but since I don’t have one, I’ll have to make due with the BM8000.

I’ll keep monitoring this tread to see if anyone has suggestions on things to try and report if I make any progress.

Glitch

[Glitch]

I like the idea of the broken turntable with a good cartridge. The downside to this is trying to explain this plan to my wife. The argument about selling the turntable wouldn’t carry much weight since my “buy-to-sell ratio” is overwhelmingly weighted towards “buy”. Also, she seems to prefer things in small packages even if they aren’t for her ;-).

Glitch

 

[Glitch]

Mark:  Thank you for the suggestions. I’ve started watching eBay for used B&O MMC’s. I looked at the Sound-Smith website and the SMMC4 seems like it would be a good candidate (and likely what I’ll get). However, it is at a price point where I’ll have a hard time justifying the purchase to my wife. I’ll also keep my eye out for a used SMMC4.

Guy:  I’m in the USA so the duty and shipping won’t be an issue.

Are B&O and Sound-Smith the only sources of compatible cartridges? I suspect that other sources are unlikely, but wanted to ask to be sure.

Thanks,

Glitch

[Glitch]

Christian,

Your reply above is consistent with what I’ve read about the B&O equipment of this era. B&O was pushing the bleeding edge at the time and reliability sometimes suffered as a result.

I’m hoping that I can get my BM6000 to show enough signs of life that it is worthwhile to spend the time and money to do a full restoration. I’m still hoping that the issue is related to an overly sensitive startup procedure and it is just a matter of figuring out what it takes to make the CPU happy enough to keep running.

Thanks again for your help,

Glitch

 

[Glitch]

Christian,

Thank you for the reply.

I just rechecked the STROBE (Digit Select) signals on pins 26-28. All three signals are always HIGH (+5v). The only time that they change is when I plug or unplug the receiver.

I’ve checked these in the past and expected to see them changing. My assumption is that all HIGH on these signals means that the display is either meant to be blank or that the CPU is not properly updating the signals. Since some of the other signals that I expect to change during power-up are not changing, like the RELAY signal, my theory is that the CPU isn’t running properly.

I think that the STROBE signals and the downstream circuitry is not broken since I was able to get the “P” display, as well as other LEDs randomly lit, when I ran the microprocessor board outside of the chassis with bench power supplies.

My interpretation of what I’m observing is that the CPU initially starts, then fails or stops at random times. What I see on the displays and other signals depends on how long the CPU runs before it has an issue. Of course, I might be having tunnel vision on this theory and would be happy to try alternative solutions.

What did you do to fix your STROBE issue on your BM8000?

Glitch

 

 

[Author]

Posts