HP 65 issue

[tangdfx]

I have a HP65. It has a perfect apperance.

And it also work in normal calculation.

But when you touch the operation related to the ram such as program function or sto number into rigester. The screen will become black and no response at all.

And I must wait for nearly 10 miniutes then I can turn on it to do the normal calculation except ram operation.

Alough I am waiting for Tony’s new HP65 CPU board.
I still want to figure out what happened on my original CPU board.
I guess the ram has defected. But the 65 has a hybrid CPU which is different with the HP67 who has an ACT.

[teenix]

Does the Last X function work?

Example

7
ENTER
15
+

Display = 22.00

g
LSTx

Display = 15.00

If this test passes, the RAM is being accessed ok, although it doesn't test all RAM.


Maybe try replacing the capacitors in the power supply.

Circuit details for the 65 can be found here in the PDF files.


cheers

Tony

[tangdfx]

I just check the Last X function is OK.
But the program function is still NOK.

[teenix]

Does the display show 00 00 in program mode?

If not maybe the switch needs cleaning and lubricating.

cheers

Tony

[tangdfx]

I think it is not related to switch.

Though when I turn the switch to PRG the display show 64 which means R/S.
Then I clear the program it will show 00 00.
And I even can start to edit a new program.

But the problem is that when I come back to the RUN mode, and click the R/S button to execute a program， the calculator will collapse again.

[teenix]

Does your program end with R/S ?

or

If you start the program with a label like [A], does it have a RTN at the end ?

If not, then the program will run continuously without stopping.

cheers

Tony