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BM6000 processor IC or complete board (non-quad)

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ipaul
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ipaul Posted: Tue, Aug 11 2020 9:18 PM

Hi all, for a BM6000 non quad version i am searching for the processor IC or for a complete board (pcb 2).

Pls send me a PM if you have any donor parts and we can agree on a price :)

Thanks.

Spassmaker
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Hi

Are you sure your processor ist dead?

Best Regards Christian

chartz
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chartz replied on Thu, Aug 13 2020 9:57 AM

Good question.

What is the problem?

Jacques

ipaul
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ipaul replied on Sun, Aug 16 2020 5:19 PM

When i plug it in it only shows :0 on the display (double dot and a zero).

Measuring the 5V for the processor it shows ok: 5,03 volt and clean.

There is no activity on the busses for the buttons and/or other I/O.

Therefore no reaction whatsoever on any of the local keys or remote.

Maybe this sounds familiar ?

(in the sm there is nothing on this 'code' in the display).

Spassmaker
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Hi Paul

Seems that you have an Oszilloscope..  elektrostaic protection is recomended.

So check following.

All 5 Volt voltages on the uPC Bord at all IC's

On uPC Board IC 6 PIN 1 schould be 3.975 MHz

On uPC Board IC 6 PIN 6 schould be 15.5 kHz

On uPC Board IC 9 PIN 14 schould be 15,5 kHz

On uPC Board IC 9 PIN 17 schould be 7,75 kHz

On uPC Board IC 7 PIN 7 schould be 7,75 kHz

On uPC Board IC 7 PIN 1 + 12 schould be 3,9 kHz

On uPC Board IC 7 PIN 11 schould be 647 Hz

This schould be measured at the uPC IC 4 PIN 15 (Time Base)

Check on uPC Board IC 4 PIN 16 50/60 Hz belonging to your Countrys mains frequency

Check the reset circurit on uPC Board IC 4 PIN 39 when you pull TP1 to Ground  PIN 38 schould go to Ground (Zero) too.

I wish you succsess

Chrischi

 

ipaul
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ipaul replied on Mon, Aug 17 2020 5:20 PM

Thank you for the tips, most of these i already measured, but...i see a strange reading and that is the 647 Hz on IC7 pin 11, this is present but only abt 2 volt TT and not 5, the others on IC7 are around 5V.

The 50/60 Hz signal is only present hen switched on according to the diagram.

Reset already checked and works ok.

I will look into IC7 because i think that 647 Hz signal should be around 5V....

All power supplies (6,5V and 5V) are ok btw.

ipaul
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ipaul replied on Mon, Aug 17 2020 6:08 PM

correction: 50/60Hz comes from standby transfo but is not present, but maybe because the cpu doesn't run (after all it is only connected to the C of TR4).

Anyway, the low voltage 647Hz is something to look into, maybe a new 74LS93 will do the trick

Spassmaker
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Hope this is the trick ;-)) Let us know

How does the signal look on IC 7 PIN 1+12 and 14

About 5 V pp?

I believe the 50/60 Hz schould be present even in StBy, I think it's needed for the clock of the timerfunktion.

The 5 V rail for the uPC is present and the StBy transformer is connected to mains.....

I don't know if it's needed for starting the Amp from StBy to On

ipaul
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ipaul replied on Tue, Aug 18 2020 7:56 PM

IC7 pins 1, 12 and 14 look ok indeed, abt 5Vpp.

The 50/60 Hz comes from a transistor with the collector connected to the processor, no pull-up resistor, so somehow it should be pulled up from the processor(?), anyway, that probably will not prevent the processor from running.

Checking datasheets the 74LS93 should have a proper high status on itself (so no open collector), hope that is the bad one, it is easier to find :)

ipaul
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ipaul replied on Sun, Aug 23 2020 4:09 PM

IC7 replaced, same result.

If i disconnect pin 11 (ic7) the level of the pulses rises to abt 4Vpp (like on the other pins).

So it seems the processor causes a load on the out[put of IC7.

Conclusion is still: broken processor IC and requestfor a donor still valid i'm afraid...

Spassmaker
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Hi Paul

So sorry that you had no success with IC7. I've no more idea what you could do now so far, hope another member has the special trick to bring your BM back to life.

Maybe you're owner of a signal generator and try to insert the 647 Hz directly into PIN 15 to see if the uPC comes to life....last chance and more experimental, but there is nothing to loose.

That is the point to make a decision.... I hope for you that someone has a uPC IC lying round in his workshop and that this wil help.

If not now maybe later Sleep

 

Best regards

Chrischi

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