Restoring HP-65

[teenix]

(01-07-2019 09:59 PM)albertofenini Wrote:  Hi everyone,

after restoring the HP65 and its card reader, we have been able to read most of the pre-recorded cards, and record some new cards.
However, what surprises us, is that we are not able to successfully write the type of cards that should really belongs to the HP65.

Look at the attached picture, we have even been able to record on both sizes of a card, and I believe that some of the cards successfully recorded are from a HP67,
while we can't succeed in writing on the first type that was coming with the HP65 itself.

Has it happened to someone before ?
Any idea ?

Does this happens on all available HP65 cards, and all of your working HP65 calculators.

If just 1 calculator then maybe the CRC circuit is not quite right.

I'm not really sure but, I think the 65 and (67 and 97) have different CRC chips, so maybe different card RW requirements ???

(01-07-2019 09:59 PM)albertofenini Wrote:  One more question.
If we record a program on a card, says about 65 steps, and then we override this with a new recording for shorter program, says about 50 steps,
will the old program overridden or the 15 more steps will remain and is this goin to be a problem ?

take care Alberto

The CRC will write to the card what ever is in the program buffer. If the program was cleared before entering your new program then unused memory will be NOP's, else it will have what ever was there that didn't get overwritten by the new program.

cheers

Tony

[teenix]

I forgot to mention, it shouldn't matter either way, as your HP65 program (longer or shorter) shouldn't access the unused program space anyway :-)

cheers

Tony

[albertofenini]

Hi Tony thanks for your reply.

You are right, the CRC from HP-65 and HP-67 are very much different, look at this article :
HP-67 Card Reader Revisited - sydneysmith.com

What surprises me is the that first card (from the top) in the picture is for sure an original a blank HP-65 card,
while among the others there are some cards from HP-67.

I was expecting the opposite, i.e. the first card working with our HP-65 and the other three not.

We have one more unit under restoration, we hope to fix the card reader as well and then we can make some tests.

We also have four more working units, but all of them have the o-ring melted and we are running out of spare o-rings.

We also have more blank cards from different years so we can make some try.

Thanks again, take care Alberto

[albertofenini]

Today we have restored the second card reader.
We had two card readers, one with a magnetic head complete but very dirty and corroded,
the second one with a better PCB but a very damaged head with some cables missing.
We decided than to mix the two.
Below you will find some pictures about the cleaning process.
We basically soap washed with a toothbrush the bakelite with the head.
The result is pretty good, although the bakelite is not as smooth as it should be.
We also lubricated the engine which still has a good worm gear and was not necessary to fix.
Head soldered to the new PCB and o-rings installed.
We cleaned the teflon parts with some soap and reassembled.

More pictures in the next post, since we are not able to attach more than 4 images per post ...

[attachment=6756]
[attachment=6755]
[attachment=6754]
[attachment=6753]

[albertofenini]

Below you will see the second HP-65 with the mother board installed,
the new card reader fitted and we tested, it can read and write cards and it can exchange
cards with the unit restored last week.

[attachment=6757]
   
   
   

[albertofenini]

And finally ..... the two units together !!!!

We really want to thank everyone during this journey, that brought us from the first picture,
a messy table with three non working units to this final picture.

We also restored the trim line put the rubber feet and we still have to fix the back label,
although we are thinking of buying some replicas for that.

Many failures, many successful steps, and still many fix to do so many things to learn.
Thanks also to the people that back in the 2004 helpd me, I have found some old posts,
on the same topics, most of the thing learned than have been of help now.

We are now looking for a donor, so if someone want to sell us a non working unit we will
be happy to buy it !

   

[jackrubin]

It seems a trivial question after reading over all your repair efforts, but I'm just getting started on cleaning up a mostly working HP-35 and haven't been able to find much information on restoring the silver trim lines on the classic handhelds.

Could you please describe the process you used to repair the silver trim in more detail? I'd also appreciate pointers to other descriptions - my attempts to search the archives on this process haven't been very successful.

Thanks!

[toml_12953]

(05-23-2019 03:13 PM)jackrubin Wrote:  It seems a trivial question after reading over all your repair efforts, but I'm just getting started on cleaning up a mostly working HP-35 and haven't been able to find much information on restoring the silver trim lines on the classic handhelds.

Could you please describe the process you used to repair the silver trim in more detail? I'd also appreciate pointers to other descriptions - my attempts to search the archives on this process haven't been very successful.

Thanks!

I've used bare metal foil with great results. It's as shiny as the original and much better than trying to use paint which never seems to be shiny enough.

https://www.bare-metal.com/bare-metal-foil.html

[rprosperi]

A silver foil pen, like this one linked below, work much better than one would expect, though note that it leaves a shiny silver paint, and not Chrome as many folks seem to expect. Most classic HP machines were shiny silver, and I think it's a very good match and quite easy to apply, though of course one must be slow and careful.

https://www.amazon.com/Krylon-K09902A00-...B00448INW6

[albertofenini]

That's exactly what we use
Sorry for the delay in replying
However there are more type that could do the job
Will post some pictures over the weekend
take care !!!

[albertofenini]

These are all of the pens we have tried out so far,
best results, however as stated not shiny and glossy as the original, were obtained with the first on the left
and the last on the right