[quattttro]

Would be a cool project. What kind of modernization were you thinking?

[quattttro]

Glitch wrote:

quattttro: Have you made any more progress? I revisited my BM6000 that doesn’t power-up properly. I was able get it to work with a known working good CPU from another BM6000. Now I’m very confident that the original CPU is bad. With the bad CPU, I observe two different (pseudo-random) behaviours when I plug-in the receiver. The first is a “:.” display, the second is a “.” display with the main amp rail relay kicking in. Glitch

No progress. Sits on my workbench, haunting me. I’m pretty sure mine has the same problem though, a faulty CPU. It is consistently unresponsive “.:”, & the main amp relay never kicks on unless I mess with the startup timing. Shame to turn it into a parts unit, but not much choice.

[quattttro]

hemenex wrote:

Sorry but if you have 15V at emitter TR27 and 14.3V at Base then TR27 as a PNP type should turn on. (0,7V on its BE-diode) I would check TR27… hx

TR27 tests fine on the transistor tester, nonetheless, i swapped it out for another one. Same thing, nothing on the collector. In any case, this is probably secondary, as the relay should not be switched on in standby mode.

[quattttro]

Thanks a lot for your help, Glitch. Hopefully I’m missing something obvious, will continue to work on it.

One final question, how does the “St.by” circuit work on board #2? Specifically around TR27. I know it gets 15V from board #6. I’ve got 15V at the DD (TR27 emitter) and 14.3V at the base, but then nothing on the collector (if I did, the relay would switch on). I’m guessing this tells me the CPU is not providing the necessary signal and TR28 is not pulling to ground? Thanks again!

[quattttro]

Same 14.7V on P42-5 with P42 wires pulled. Interestingly, I get “P” in the display when P42 is pulled. It never displayed anything before save for the colon, dot, and radio LEDs.

Definitely have both 5V supplies. I get a perfect 5V at the CPU pin 40 and the other ICs on board 2 are all getting 4.9v from the 2TR1 supply.

I am getting some sort of signal from the CPU’s 50/60Hz pin (16). The waveform looks exactly like your did on page one of this thread. Even has the same blip on the right side of the square.

 

[quattttro]

I’m probably getting desperate, but would 14.7 volts here cause a problem? I know this 15v goes to the standby circuit amongst many other things. And I’m not getting 5V on Pin18 of the CPU (st.by), though i’m probably running into that chicken/egg problem again 🙂

I’m getting 14.7volts at pin 3 of IC2 (board 16).

[quattttro]

Adjusting R25 solved the motor always-on issue. The full calibration procedure requires the receiver to be on so the volume can be adjusted to various levels.

[quattttro]

Perhaps unrelated, but I noticed resistor R27 has been snipped out of my motor control board. Looks to be related to the volume control. Is this a factory thing, or should I install a 470 ohm resistor there? I noticed the resistor present in Sonovor’s thread, here.

 

Missing R27:

[quattttro]

Ok, thanks. I guess i was following it backwards.

My machine does not power up. When plugged in I only get the standby light and clock colon. The radio LEDs glow and volume motor spins endlessly too (despite pot position). Nothing happens beyond that. Buttons do nothing.

[quattttro]

What about Pin16 on the cpu (the 50/60Hz signal)? This signal comes from TR4 on the power supply board # 16. I’m not getting a square wave from the collector of TR4, but I might not be measuring correctly. Is this signal required for CPU startup?

[quattttro]

It does now, yes.

[quattttro]

Exactly. Mine has the same mark/cut. Part of the modification, I guess.

In other news, after replacing R89 again, I was able to get around 2.3V across R95. Did not solve my issue, however, as the 6000 still won’t fire up beyond colon and standby dot on the display.

[quattttro]

Perhaps this is normal, and part of the modifications for the extra add-on IC board, but I noticed this trace in red between IC4 (38) and IC9 (pin 11) was severed. Should it be?

 

[quattttro]

Just to confirm, I remove P5 connector completely, inject 4.6V to pin 3/4 of P5, then monitor the voltage across R95 with a multi-meter (service manual says to use an oscilloscope).

One thing i’m unclear about is the ground situation. If I understand correctly, removing P5 also removes the chassis ground wires from microprocessor board 2. I would need to connect power supply ground to a ground point on board #2, and not the chassis ground point up by the amplifier board.

 

Thanks again, Glitch.

[quattttro]

Ok, using a series resistor and a power supply, i think 2D6 tested OK. The transistors TR5 and TR6 tested OK on the tester too.

I re-did the Reset adjustment procedure after testing. After moving the ground connections from the power supply around I was able to see 3V on R95, but adjusting R89 did not change this voltage at all. I’m at a loss 🙁

Thanks for the help!

[quattttro]

I pulled D6. In diode test mode on my MM, i get 0.6V one way, then 1.28V in reverse. It should be OL or infinite in reverse, am i correct here?

[quattttro]

Yes. 6.5V on P2-2 and 5V on P2-3.

[quattttro]

yes, 5v CPU (pin 39, iirc) and the other voltages are all exactly as noted in the service manual. I did try to adjust the reset circuit, but I get 0V across R92. I’m not really sure why that is.

[quattttro]

Did you ever figure out if the CPU was dead on your 6000? Mine exhibits the exact same symptoms, unfortunately.

[quattttro]

y’know the springs you get in picture frames to push the backing against the glass? Those work well as an alternative.

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