HP-45, PSU and testing points

[albertofenini]

Hi everyone, today we dealt with a two HP-45.

Both were not running, we fixed one and we are looking for help for the other.
Doing this, we recovered some testing points from the schematics and we are happy to share
them, may be could be useful for someone else.

The one that we fixed had all of the Voltages correct, except for Vcc which was about 3 volts,
and all of the waveforms were correct. Display was close to dead. Also Ø1 and Ø2 were good.
We replaced the diode were Vcc is measured (top of the logic board) and it worked like a charm.

The second one one is more tough.
Display is completely off, and the two transistors from the PSU get very very hot.
We replaced them with a couple of transistors from another calc but with no improvement.
Also this couple of transistors get very very hot.

What could be a possible cause for this ?

More in general, has anyone found a good replacement for the diodes, capacitors and transistors for a PSU ?

The transistors are marked F4 094 427 and 0550
The diodes should be 1N4148 except for the zener
we don't know the voltage value for the zener
Capacitors should be replaced with tantalium or with Electrolytics ?
The disc capacitor I think is a ceramic one

Thanks for any advice on this subject !