HP-65 logic board repair - help required


ciao a tutti,

last summer I have tried to repair an HP65 board,

the project is still open, I have got stuck in searching for replacements parts for the PSU, but I'll work on it again in the near future.

Now, I'm dealing with another one :

The board looks clean, even if I think that the circled diode has been replaced in the past.

This is how the display looks like :

The first thing I have done has been to measure the three values

Vss = 6.38 V

Vgg = -12.40 V

Vcc : 7.91

which look good to me, very close to those of a working HP65 I have.

So the question is, what could be wrong ? The Hybrid ?

What can I measure any further to troubleshoot the board ?

Thanks again for help, Alberto


Alberto, check your clock signals next, PHI1, PHI2 and SYNC. Refer the document I sent you, if you can't find it, email me and I'll send it again.

John Robinson

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP9810A and HP9862A - ROM required? Thomas Falk 0 498 12-07-2013, 09:49 PM
Last Post: Thomas Falk
  HP-65 short circuit Ignacio Sánchez 2 597 10-22-2013, 08:27 AM
Last Post: Ignacio Sánchez Reig
  HP-65 Video Tapes - Anyone have a Copy? Bill (Smithville, NJ) 3 744 10-09-2013, 07:40 PM
Last Post: Paul Berger (Canada)
  Using your HP-65 as a clock! Don Shepherd 24 2,361 10-08-2013, 11:53 AM
Last Post: Don Shepherd
  HP-65 to kill... Benoit Maag 11 1,295 08-15-2013, 08:18 PM
Last Post: Jake Schwartz
  OT: My brain is failing me again. Help with numerical / mechanical problem required. Harald 4 700 07-01-2013, 10:31 AM
Last Post: Harald
  For sale: HP 25C and Stat Pac 2 for HP 65 Michae Altmann 1 466 04-21-2013, 01:24 PM
Last Post: Raymond Del Tondo
  Repair my HP 65 motor? Michae Altmann 1 460 04-13-2013, 10:03 PM
Last Post: aj04062
  Repairing HP 65 Michae Altmann 5 753 03-15-2013, 04:13 AM
Last Post: Joel Setton (France)
  RPN logic question Victor Quiros 52 3,788 03-12-2013, 02:59 PM
Last Post: Victor Quiros

Forum Jump: