HP-65 1603S03504 - display not working at all

[teenix]

(11-13-2020 09:46 PM)albertofenini Wrote:  Hi Tony
No way ! We removed at first the anode driver and took all the measures
Voltages all around are correct and in the right places
However RCD and all of the Disp* are flat and at zero value
Then we removed also the cathode driver and measured everything again
Same as above
Should we try to remove the coils as well ?
What are the chances the all of the leds are burnt ?
We have uploaded couple of pictures of the pcb without the drivers and there are no signs of short circuit whatsoever
Thanks again for all the support
Take care !!

It seems that the oscillator may be faulty then. This is the 330uH inductor and the 150pF capacitor under the displays and these form an LC oscillator.

I would replace both drivers and measure the 01 and 02 input signals on pins 7 and 8 of the anode drive which also appear on pins 40 and 41 of the hybrid. Pins 38 and 39 are the 01 and 02 out signals that feed the ROM chips.

If these are flat then it is possible that those LC components are faulty, bad connections, bad PCB trace or the anode driver is faulty.

cheers

Tony