Hi

Are you sure your processor ist dead?

Best Regards Christian

Good question.

What is the problem?

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).

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

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.

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

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

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 :)

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...