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Image of inside of HP71B HP-IL module
08-01-2020, 10:50 PM
Post: #1
Image of inside of HP71B HP-IL module
I have a pretty clearly damaged HP-IL module and would like to see what the contact area should look like. If anyone has a working 82401A HP-IL module and would be prepared to lift off the metal cover and take a few close-up photos I would be very grateful indeed. I think there may have been small metal fingers on the pads, but all that is left is a roughened solder surface, and two pads are missing but have no obvious traces to them. The main calculator just has a set of flat edge-connector-style pads.
My module does not appear to the host HP71B so there is almost certainly a contact problem, at the very least.
It seems a real shame to just junk this module as it might be persuaded to work again.
All help gladly received.
Jeremy
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08-02-2020, 04:59 PM
Post: #2
RE: Image of inside of HP71B HP-IL module
From the HP 71B Compendium.

[Image: HP-82401A_IV1.jpg]
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08-02-2020, 06:07 PM
Post: #3
RE: Image of inside of HP71B HP-IL module
Beware, there are two pins that are missing from my module picture.
I still need to find time to solder them to make the module work again.
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08-02-2020, 06:23 PM
Post: #4
RE: Image of inside of HP71B HP-IL module
From one of my HP-IL module:

[Image: chpilmod.jpg]

Can you post pictures of your damaged module?

J-F
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08-02-2020, 06:26 PM
Post: #5
RE: Image of inside of HP71B HP-IL module
This image from the Hardware Design Spec may help visualize replacement contact fingers.
   

The fingers look to be about 10 mil thick (0.010", 0.25mm) phosphor bronze that you may be able to fashion for yourself from sheet. Another possibility might be half-round jewelry wire of the right gauge. Anything that makes contact will do, since you're unlikely to remove the module once it works!

Who decides?
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08-02-2020, 07:00 PM (This post was last modified: 08-02-2020 07:02 PM by pamphonica.)
Post: #6
RE: Image of inside of HP71B HP-IL module
That's enormously helpful. ALL the fingers on my module are missing! And two pads are damaged, and one pad is lifted (not obvious in photo).
I'll need to do some very fine soldering to replace them. Phosphor Bronze is probably a good idea.
It's interesting that this module came IN an HP71B, but the fingers were nowhere to be seen, so the seller must have known it was bust. I got a large rebate!
Photo attached.
Thanks everyone,
-Jeremy


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08-02-2020, 07:52 PM (This post was last modified: 08-02-2020 07:55 PM by J-F Garnier.)
Post: #7
RE: Image of inside of HP71B HP-IL module
I can't believe that the contacts have been accidentally damaged. It seems to me that they have been deliberately removed. For what purpose? Not to wire the module inside the HP-71B case, as can be done with RAM or ROM, because it would not fit due to the HP-IL connector.
Maybe have they been reused to repair another module.
In the same way, you may try to find a cheap module like a low-value 4K RAM to get replacement contacts. Soldering them in the right position may be tricky.

J-F
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Yesterday, 10:54 AM
Post: #8
RE: Image of inside of HP71B HP-IL module
I agree - they seem to have been removed, maybe to repair something else. Of course this module may well prove to be dead when I put the new fingers on!

There are differences in shape (bending) between your excellent photo above and the technical design drawing. But I can see what shape the contacts have to take, and I expect I can replicate that. I have found some 0.4mm phosphor bronze rods on Ebay that look promising. I will probably have to make up a jig to keep the rods in place while soldering them.

But that's a job for another day. Meanwhile, I hope that a working module will soon be on its way to me. Then I can check things out in the HP71B
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Yesterday, 08:23 PM
Post: #9
RE: Image of inside of HP71B HP-IL module
When soldering module pins it's helpful to tape them all together to maintain alignment.

https://photos.google.com/album/AF1QipO_...A7-yz1dRz4

The tape in the pic is relatively antistatic however do NOT use regular cellophane tape.
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Yesterday, 11:53 PM
Post: #10
RE: Image of inside of HP71B HP-IL module
(Yesterday 08:23 PM)Dave Frederickson Wrote:  The tape in the pic is relatively antistatic however do NOT use regular cellophane tape.

I get a 404 error when I try to view the picture.
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Today, 02:26 AM
Post: #11
RE: Image of inside of HP71B HP-IL module
Same here. It appears the file was not set to public, as gDrive forces me to sign-in, and then fails with 404.

--Bob Prosperi
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