HP41 band aid ... ?

[ThomasF]

Hi,

Does anybody recognice this piece of flexfilm?
I found it amongst some old stuff from my PPC-time and probably sent to me during that time.

   

The size of it (~36mm wide and 21 connectors) correspond very well with the module-connector of the 41 (ie between the battery/module-bay flex PCB and the keyboard PCB.
It fits very well there, but I can't figure out the usage for it, since there is really no room for any expansion there (ie build in modules etc).

   
(Edit: Just a photo-montage - I had no open 41 at hands ...)

Cheers,
Thomas

[brouhaha]

(02-06-2023 01:41 PM)ThomasF Wrote:  The size of it (~36mm wide and 21 connectors) correspond very well with the module-connector of the 41 (ie between the battery/module-bay flex PCB and the keyboard PCB.
It fits very well there, but I can't figure out the usage for it, since there is really no room for any expansion there (ie build in modules etc).

That was in fact for wiring modules inside. I used one of those to put an 82182A Time Module in my 41CV. You have to extract just the PC board fr9m the module, but then you can squ3eze it in.

[ThomasF]

Thanks for the confirmation!

I have soldered a lot of modules within the 41 back then, but always directly on the PCB.
This is probably a better way to non-intrusively solder the modules inside, with the possibility to remove them without leaving any trace.

Cheers,
Thomas

[anetzer]

(02-07-2023 03:18 AM)brouhaha Wrote:  That was in fact for wiring modules inside. I used one of those to put an 82182A Time Module in my 41CV. You have to extract just the PC board fr9m the module, but then you can squ3eze it in.

Very interesting!

Was this an HP original part? Did HP include modules into some HP-41 models using it?

I'd like to see, how the inside of such an HP-41 looks like with that flex strip and a module in place.

Totally ludicrous: Are these strips still available?

Thank you!

[ThomasF]

(02-07-2023 05:04 PM)anetzer Wrote:  Was this an HP original part? Did HP include modules into some HP-41 models using it?

No, this was not a HP product, and I have never heard that HP supported this in any way (to eg. include modules inside the calculator body).

This was sent to me as a product sample, but I have not saved the companion letter, nor is there any indication on the flex of who manufactured it (apart from the indication of pad 1, pad 21 and the text "STARTCO" (which actually might be the company) there is nothing to be found there).

Maybe something could be found in PPC/CHHU journals, or in the EduCALC catalog, but personally I can't recall seeing anything about it.

But maybe someone knows more about it ... ?

Cheers,
Thomas

[mfleming]

(02-07-2023 05:04 PM)anetzer Wrote:  Totally ludicrous: Are these strips still available?

If you can get the dimensions and layout, Osh Park makes flex PCBs so you can play with a few on your own.

[Didier Lachieze]

Looking at the pictures it seems that the traces are masked except at one end where I suppose they make contact with the HP 41 modules flex PCB. So I’m wondering how do you connect an internal module board to these traces?

[brouhaha]

(02-07-2023 11:41 PM)Didier Lachieze Wrote:  Looking at the pictures it seems that the traces are masked except at one end where I suppose they make contact with the HP 41 modules flex PCB. So I’m wondering how do you connect an internal module board to these traces?

I think the other side had another unmasked section. I haven't seen it since 1982, though, so I'm not 100% certain.

[ThomasF]

(02-08-2023 12:11 AM)brouhaha Wrote:  I think the other side had another unmasked section. I haven't seen it since 1982, though, so I'm not 100% certain.

Yes, the flex on one side has the "long" pads of which only a short bit is unmasked (gold plated) and the rest is "leaded" for easy soldering of wires. This side also has the text and pad-numbering (1 and 21), and it looks as if the flex is manually cut, since the sides are not perfectly straight.

The gold-plated pads have corresponding pads on the other side, and the pads are connected by via-holes, so the idea is to place the pads right between the 41 keyboard PCB and the module bay flex, and "extend" the pads for easy access for adding something inside the calculator.

Tried to measure the flex with the following result:

Code:

         Overall width (W): 38.9 mm
         Overall hight (H): 31.1 mm
            Pad length (X):  5.1 mm
         Stripe length (Y): 22.5 mm
Overall CC (pad1 -> pad21): 35.11 mm
           cc (via to via):  1.76 mm

       
(Edit: updated picture with cc)

Cheers,
Thomas