HP-65 1333A04841 restoration it doesn't work anymore ...

[albertofenini]

Hi everyone,

after two days of sitting on a heater the CPU board is now (mal)functioning again

It doesn't turn on at the first try, but after a couple of tries it stays on and performs calculations
also small programs have been written and tested

We have checked the main voltages and with a Batt of 3.9 V we have measured the following
Vgg - 12.56, Vss (no card reader connected) 6.4, Vbsw 3,844 and Vcc 7.96

Also, we have measured Ph1 in, Ph2 in, Ph1 out and Ph2 out and these are also ok
as you can see in the updated photo album

However, it doesn't read nor write cards

We have then swapped this CPU board with a working one S/N 1333A20064 and this assembly
(1333A04841 card reader with 1333A20064 cpu board) is reading just fine, RA and RB are also
in the updated photo album

We may say the card reader (at least for reading) is working and the wheel correctly sized and aligned

We have then put back the original CPU board, and surprisingly the RA and RB curves are also fine
but still the unit gives error at the end of the card reading operation

As a counter test, this CPU 1333A04841 with the other unit card reader 1333A20064
is not reading as well, so is safe to say that this is a problem specifically with the CPU board 1333A04841

What could it be and what can we further check ?

Also, since it still does not turn on at the first try, is it worth to change all the caps ?

Is there a more precise method to test if the gummy wheel is correctly aligned
(like measuring the current drained from the motor ?)

The updated album is here :updated album HP-65 1333A04841

Thanks to everyone and take care, have a good weekend !