(03-13-2021 12:12 PM)AndiGer Wrote:  Hi Tony,

Look into this thread - especially last post:

https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv009.cgi?read=24353

Tony Duell mentions pin 8 is the power supply pin on all small IC chips inside a spice. The C models have this IC pin directly connected to PSU / battery to retain RAM content.

Andi

(03-13-2021 01:51 PM)teenix Wrote:  If anyone knows, I take it that carefully un-clipping the 6 internal plastic retainers (3 on each side of case) will allow more access to innards.

cheers

Tony

cheers

Tony

(03-13-2021 05:28 PM)PANAMATIK Wrote:  I had the same missing pin 8 on my HP-33E.

I could attach a wire to it after using a Dremel tool to get more contact area. See this thread Post #9

https://www.hpmuseum.org/forum/thread-3325.html

good luck
Bernhard

(03-14-2021 03:28 AM)[kby] Wrote:  Are you talking about opening the spice case?
Iirc you actually need to twist the top and bottom relative to each other. I think it was pre-pandemic when I opened one so can’t recall for sure but I recall it isn’t obvious how it fits together until you take it apart. I don’t remember clips, but if they are just “obvious” I think I got stuck after that; it is the bottom edge (front of the calculator in operating position) that will then be stuck and that is what requires the twist. I think there was something written by Geoff Quickfall that detailed how to open with this technique.-kby

(03-14-2021 07:42 AM)teenix Wrote:  I assume 3V will do. Do you know what polarity the battery terminals are? The battery terminals are on about a 25 degree angle on the small pcb, do you know if the upmost is +ve or -ve?

(03-14-2021 10:47 AM)teenix Wrote:  Hi all,

I just had my first experience with the innards of the HP-3x series and I'm sure as others would have found they seem built more around cost than maintenance.

The repaired IC pin did not work when I connected to my power supply - about 2.7V. After removing the inner plastic frame and looking around, the ribbon cable has corroded and split which seems a common fault.

I'll try a fix, but it could be a candidate for Bernhard's repair kit if the owner is interested.

cheers

Tony

(03-15-2021 12:16 PM)ThomasF Wrote:  Hi again,

Just checked on my HP-31E, and yes, 2 out of 3 chips (the silvery ones) are both missing pin 8. Doesn't show very well in the picture, but locking close I can see that the pins are missing. My model is the original, clamped version i.e. not soldered, and the pins are really cut, not burnt away.



And yes, the device is in excellent condition, works like a charm!

EDIT: Found these notes as well, in this case (a HP32E) only two chips are present - no dummy (without pin 8) was present in this device.
https://www.keesvandersanden.nl/calculators/hp32e_repair_2.php

Could it be that to keep the correct pressure between the pads and the pins, HP included dummy chips to fill the compartment that are normally used in other models? I also noticed that the chips are marked - in my case only the first chip has readable identification - but the other two was just covered in silver paint.

Cheers,
Thomas

(03-16-2021 03:32 AM)teenix Wrote:  Hi all,

I removed the pin 8 connection again and put a dap of epoxy on the chip where I Dremmelled the plastic away to protect it against moisture ingress.

I repaired the corroded and broken battery ribbon and what do you know, it sprang back to life :-)

cheers

Tony

(03-17-2021 09:56 AM)PANAMATIK Wrote:  

(03-16-2021 03:32 AM)teenix Wrote:  Hi all,

I removed the pin 8 connection again and put a dap of epoxy on the chip where I Dremmelled the plastic away to protect it against moisture ingress.

I repaired the corroded and broken battery ribbon and what do you know, it sprang back to life :-)

cheers

Tony

Does it work without the chip? In this case moisture protection is not really necessary?

Bernhard