Spice Display Module

[teenix]

Hi all,

Somewhat of a bummer.

The Spice display module I was using to develop the Spice CPU board started playing up more so than usual. The exponent unit digit never worked and I could see that the LED digit chip was sitting crooked and was only being held in place by the multiplexed anode wiring.

It looks like last of these miniscule wires finally broke, and the chip was free to move about under the display lens assembly and this managed to short some of the other digit's multiplex wiring causing multiple segments to light. I doubt this is ever repairable especially with my old sexagenarian nervous system.

I had one more Spice display to play with, but the 2 exponent digits didn't work. The chips looked ok although slightly larger than the others, but when I removed the lens cover, these two LED chips had dislodged as well and were "floating", held in place by the anode wiring. I powered up the digits and as soon as the chips were gently pushed down and common cathode contact was made with the circuit board the LEDs started working again.

I don't know how these LED digit chips were originally mated with the circuit board, ultrasonically welded or something, but is seems over time the joint becomes unstable. How to fix? I have no idea other than some sort of conductive glue which can somehow be placed between the chip and circuit board without disturbing the almost invisible wires. These chips are about 1 x 2mm in size.

I guess Spice calculators might need some cautious handling lest a sharp rap causes one or more of these display contact joints to break away.

cheers

Tony

[rprosperi]

Tony - I have a Spice board I'm happy to send for you to scavenge the LED from, but it will take some time from NY to Aus. If no closer options emerge and/or that's of interest, let me know and I'll dig it out and mail it. If so, please PM me your address to ship to.

[spikeofax]

Likewise, Tony. I have a "loose" machine that I can send down from the UK if that would help. Andrew

[John Garza (3665)]

There are occasionally Spice (and Woodstock) LED display modules on ebay. Around $27 last I recall.

-J

[John Garza (3665)]

The LED modules in Classics were far superior. Encapsulated, they provided mechanical support for the thin wires. I think the reason we see so many Spice machines with missing segments in the display is due also to the poor battery well design. Most users are accustomed to slapping the calculator on their palm to remove the battery pack. Unlike the classics where the battery just falls out once the door is removed. Maybe to save money HP just hired less capable engineers? -J

[John Garza (3665)]

The Woodstock LED modules seem built in a similar fashion to the Spice modules. But you rarely see missing segments in Woodstocks like you do in Spice machines. And the Woodstock battery well design doesn't invite sharp knocks to dislodge the batteries. -J

[Harald]

(03-28-2023 12:18 PM)John Garza (3665) Wrote:  The Woodstock LED modules seem built in a similar fashion to the Spice modules. But you rarely see missing segments in Woodstocks like you do in Spice machines. And the Woodstock battery well design doesn't invite sharp knocks to dislodge the batteries. -J

Never thought about this, but you might be onto something there.
I always thought the main reason for dead spice displays was leaking batteries. But maybe that is not true.

[teenix]

Hi all,

I had a fiddle with the Spice display with the dead exponent digits where the actual LED digit had dislodged from the circuit board and was hanging on by the tiny wires. I knew the segments work if the digit was pressed against the circuit board which is the common cathode connection.

I purchased some silver conductive "glue" which is available for a few $ on "you know where", and I carefully applied a miniscule drop between the LED module and circuit board.

Pressing it gently back in place and straight away the LED segments worked again, although there was a short between some segments. I had to try to fix this by trial and error because I didn't know which were shorted, so as careful as my shaky old hands would allow, I managed to separate the offending wires.

Unfortunately, the extra fiddling dislodged 2 wires on the exponents digits again and 2 segments do not work. I have no hope of reattaching them, so after all that, it will be a dud again.

The wires and the joints are so old tiny that I think if you breath on them too hard they will break apart at the joints. If you had the right tools it could be fixed, but they are something I'll never see.

If you have a Spice module with a dead digit, it may be worth a "careful" silver glue fix. If it is a segment or two, then best of luck with the wires. If you notice a display digit that looks crooked, it might be floating and worth a fix before it gets worse.

The lens assembly separates easily by breaking off the ends of the brittle (acrylic?) heat stakes. I just used sharp side cutters.
Be very careful that the lens does not rotate or slide sideways when lifting it off, or you risk dislodging the digits and or breaking or shorting the wiring.
It should go back together with some hot glue.

The moral here maybe...

To avoid paying the price
with your precious Spice
just treat it nice

cheers

Tony