HP-65 goes on hold after reading a card

[teenix]

I can only go by the block circuit diagram for the HP-65 which has a separate storage circuit for the programs, which is the 600 bit (plus program and return pointers) carousal buffer.

This is connected to the CRC chip via 5 lines for control, timing and data.

It is also connected to the CTC chip, which probably controls access to the program steps and pointers. This may also have a problem.

It would seem that there is a problem within this arrangement, either the storage/retrieval logic or the buffer itself. If this is the case, and as there is no easy way of changing these chips or checking the internal connections, then I would guess that changing the hybrid may fix the problem.

cheers

Tony

(11-28-2020 08:34 PM)albertofenini Wrote:  Hi Tony, Hi Everyone
we did a couple of tests, using the Biorithm Program which is 90 steps long

It reads ok from a card but if we examine the listing, after few steps a - minus appears at the right of the instruction code.
Usually this would mean that the end of the 100 steps memory has been reached, obviously this is not true.

The minus appears in multiple positions like at the 12th step, then at the 15th step, then in more positions but not in all the steps after the first appearance.

The unit goes on hold even just pressing RTN in the RUN mode after all the steps have been examined

We tried reading from different cards with the same result and if these cards
are used with a working unit everything runs ok.

If the program is inserted with the keyboard, everything goes well until about the step 70th,
after which more steps can still be keyed in but all will have the minus at the right of the instruction code.

Looks like not all the memory is working and can be used

Is there any possible fix ?
Is the problem in the Hybrid or somewhere else ?

Thanks for any possible hint !
Take care !