Another HP-67 repair query

[teenix]

(10-14-2020 11:58 AM)coitboy2000 Wrote:  OK, thanks I will keep probing. Any thoughts on why the display is still blank Is it likely any of the components may be the reason ? i.e are capacitors, resistors, transistors ever the reason ? If only there was a whole suite of published base voltages throughout the circuit for beginner electronics people like me. Its hard to hunt down faults.

I appreciate your replies.

It could be multiple things unfortunately. ROM ACT etc. It would be hard to tell without checking with a scope on how the data busses and display drivers are operating.

I'd still try unplugging the card reader board from the CPU board and make sure it is not shorting anything and try the power again.

cheers

Tony