SR-52A rebuild project (SR-52A 942058 LTA4176)

[albertofenini]

Hi Gene

You know we have a thing for the HP65 and the HP67

We have repaired literally tens of them with great support from the people of this forum
Still, in high school I had a 58C and I also have a bond with TIs

This is the third SR-52 we repair, all of them can read and write cards although the others two are in definitely in better shape,
nevertheless also this unit when finished will come out nice

We have also repaired our three TI59s and all of them can read and write cards

And I can tell that all the cards recorded on the SRs are interchangeable within those models as are those written by our TI59s

It’s true, they are less repairable but still the support we have received
from members of this section of the forum was priceless and without it
we probably would have not been able to fix them

It’s true the card reader mechanism is simpler, almost basic if you want but it
does its job

I can’t tell which one I prefer, both HP and TI brings back memories for me, I would say the HPs are probably more reliable and tent
to last more but all of these are beautiful pieces of history

A special thanks to the moderators of this forum and to all of the contributors
without each and everyone of you guys it would not be possible to have fun and share ideas

Keep up the good work !!!!!

We are more than happy to share our small experience hoping it will be useful to somebody

P.S. next week we’ll be receiving an HP67, a SR52 and two TI59 so will see ...

[albertofenini]

The faceplate

Small update ...

After a week of being pressed together
we have found out that the faceplate was not perfectly aligned
with the plastic case
As a result the lower keys were not moving freely in their holes

We have removed the faceplate and changed the bi adhesive
This time we also mixed types
On the external we used the 3M which is stronger
In the rows a thinner one
Will see tomorrow ...
Pictures here : SR-52 rebuild project

[albertofenini]

Hi everyone
raining Sunday so we worked a little at the bench on this unit
not much success though...

the faceplate, after we changed the bi adhesive, is a bit better but the thinner one we used
is not so strong ... as a result the faceplate between some keys is not as flat as we would like

the idea of using a connector for the keyboard was good but the wires we used were too rigid and
too thick, handling the keyboard for re assembly had damaged the traces on the
keyboard board, so we went for something thinner which we soldered

we have left the connector as removing it could have possibly damaged the traces
on the main pcb

all in all and considered what was this before is not bad

sadly the card reader behavior is become very unreliable and it reads one card out of ten
we think that is possibly due to the size of the roller, which was good for the other three units
we restored but not for this, although when the unit was dismantled it was steadily reading
we will try something different and post here the progress

updated album here : SR-52A rebuild project (SR-52A 942058 LTA4176)

as always any suggestion is welcome !!
take care !!

[Nicoverduin]

I have 2 x SR-52. one is working but the cardreader needs fixing. The other seems to work but the keyboard PCB is a mess. The tin (paint?) is gone in several places and I was thing about making new ones. Anyone done this before? Or is this my next coming project ?


Is also built these new battery packs from this project https://hackaday.io/project/176529-ti-59...ttery-pack and used that design to create my own BP7/8/9 packs to generatate 9V. No more NiCd batteries but Li-ION 1000/1200 mAh. see https://hackaday.io/project/194400/galle...b92a52ba66

The casings are 3D printed on my Creality CR-10S pro

[Nicoverduin]

I have decided to make a new keyboard for the SR-52 as my keyboard has lost too much of its conducting ink traces. Spent a wholde day of measuring (everything in inches instead of mm). I used the schematic/diagrams from Jose Mesquitas. So I do hope they are correct

As the currenct PCB is 2,2 mm thick I willl redesign the supporting frame between the main PCB and keyboard in autodesk inventor and 3D print a new one as the common JLCPCB circuits are 1.6 mm thick.

Next step is to try to get a 100% correct size pcb diagram out of my laser printer first, glue i on some cardboard and verify the measurements are correct before sending it off to China.

Until the next post

Regards
Nico Verduin
Netherlands

[Nicoverduin]

I found these nice little 4x4mm membrane switches. This would save me a lot prolems with the loose disc membranes currently. I ordered 150 of them for a total of about 10euro. Test a few when they come in and if they are ok I will use them.

I will see if someone can cut the PCB tomorrow at my school so I can verify it will fit before sending it to China for production.



To be continued

[Nicoverduin]

And a new support frame

[Didier Lachieze]

Very interesting project! Thanks for sharing.