Restoring HP-65

[teenix]

(11-25-2018 09:59 PM)albertofenini Wrote:  PROBLEM 1 : If I put the CPU under restoration I didn't have the control of the last two rows of keys. This can't be because of a bad keyboard, since the unit housing the CPU is the working one.
So I re-passed the soldering points of the hybrid on the side that control the keyboard rows (I do have the schematics), and it has got worse, since now most of the keys are not responding

Then I did the opposite : I have put the working CPU in the cases with KBD001 and KBD002. Both appear in very good conditions as you can see from the pictures, and in this test the CPU board is working since is coming from the working unit.
KBD001 as a weak metal plate, you don't hear the classic click when a key is pressed, kind of stressed metal. But if all the keys are pressed strong enough they work.

The keyboard connectors on the restoration CPU look black with corrosion, maybe some of this black is in the pcb holes and is not making good connection to the keyboard pcb pins.

Sometimes the component pins have corrosion on them and new solder will not properly fuse to them causing open circuits or high resistance joints.

Just guessing, but it may be possible that resoldering the hybrid pins caused damage to the module, open circuited the pins as described above, or internally, too much soldering iron heat, static damage.

If the exact same problem exists between the different keyboards then the hybrid would be suspect and or the keyboard to CPU connectors.

(11-25-2018 09:59 PM)albertofenini Wrote:  PROBLEM 2 : when the working CPU is put in the case with KBD002, on few led lights on ,as you will see in the picture.

Does the display change when keys are pressed? If so, it might be the same problem. Corrosion on the keyboard to CPU connectors.

cheers

Tony