HP-65 more on the card reader

[teenix]

(02-12-2019 11:38 PM)albertofenini Wrote:  No way !
We did few tests tonight without getting any far from where we were.

At first we de soldered the wires, as said they have been of no trouble with the other units, but you never know.
By doing this, we also checked for cold joints and re-passed all the joints.
Then we cleaned the prongs and the corresponding holes in the logic board.

We assembled and powered the unit with an external battery pack, not the original.
To our surprise it worked like a charm.
I say to our surprise because in our opinion we didn't do anything special other than cleaning what was already cleaned.
We read and recorded almost the entire Standard Pac.

Then the external battery (3 X AA rechargeable Nimh batteries) died ...
We used then the rebuilt original battery pack, and the card reader began to fail in recording.
We changed batteries in the external pack and we switched back to that and
the card reader started to work again.

At this point we thought that when the renewed original battery pack was inserted something was changing (mechanical pressure maybe ?) but don't ask me what.

We also changed the rounded o-rings with some squared o-rings, trying to improve the friction between the card reader and the card, and it got worse.

Since we have an additional spare card reader, which we know it works because we have used it with the HP67 and it works 100%,
we swapped the actual card reader with this one, just to get back to the starting point. It reads well, but it never record.

We almost tried every possible position with the eccentric, and I must say that while reading is affected by this setup, while recording doesn't work regardless of the eccentric position

As always, we are opne to any suggestion .... thx for help !!!

If I understand correctly, if a different battery pack works and the original doesn't, then perhaps the battery pack may be faulty, ie higher than normal internal resistance, poor terminal contact. When writing, the sense amplifier probably needs more current than reading and this may be affecting the battery supply, or the chip has decided it wants a low impedance battery supply.

It could be just a weird combination of this particular chip and this particular battery. Does that battery cause faults in other calculators?

cheers

Tony