Another HP-67 repair query

[coitboy2000]

(10-14-2020 06:13 AM)teenix Wrote:  

(10-14-2020 05:40 AM)coitboy2000 Wrote:  Hi all

I am trying to repair an HP-67 I purchased as not working.

- when connecting the battery terminals to by bench powers supply I notice the red led dot illluminates when I supply less than 3.6v. It draws about 90ma current.
- increasing the supply to 4v max the red light dissapears but the display is blank. The current draw increases to 110ma
- Initial probing indicates voltage is transferring to the cpu board but only 4.5v or so max.
- the sense amp chip gets pretty hot to touch. Normal ?

Cheers

Richard

The low battery indicator appears to be working.

The sense amp definitely should not get hot. Try carefully unplugging the sense board from the CPU board and try the power again.

cheers

Tony

Ok, I will try that and report back. Thanks.