P2/P3 Display Variations

[abem]

Hi.

The other day I had someone ask about a Hamilton QED where the colons are a bit brighter than the other dots. I explained that rather than being a defect, this was just a characteristic of how some of the displays were built. To show this more clearly, I took a few close up photos which I thought I might share with the DWF (see below).

My impression is that the displays with the brighter "L" shaped colon dots came a bit later than the ones with the smaller rounder colon dots, but I could be entirely mistaken. I'm not sure if they are made by different manufacturers or not - I think both Litronix and Monsanto were building them.

In any case, I find the tiny micro-structure of the early P2/P3 displays kind of amazing with the tiny discrete bars of silicon, each with 5 dots, carefully arranged into tiny digits. If anyone knows how these were made, I'd love to hear the story.

Cheers,

-abe.

Display Variation #1:

DSC_9359 (900x600).jpg

Display Variation #2:

DSC_9366 (900x600).jpg

[charger105]

I've never looked this closely at the displays, nor noticed any particular differences in P2/P3 displays.
I like the snow-flake (or asterisk ?) shaped dots on the upper display. I wonder why they made them this way ?

[bruce wegmann]

These are not variations in the sense that someone was doing it one way, one day, and decided to do it a different way, another day. What we see here are two different manufacturers (who were actually very consistent, individually). The upper pic is of a Monsanto LED, the lower, Litronix. They can actually be distinguished visually, even when un-illuminated; the Monsanto LEDS have the aluminum electrode covering most of the LED chip, giving them a slightly silvery appearance in bright light. It should be noted that some of the Litronix LED chips are actually signed "Litronix", but you need at least 60x magnification to read it. There are true variations on the height of digits on the P4 and Dress models (as much as .2mm...not a lot, but still visible). And, of course, there are the very rare bar-segment displays found on some early Ladies modules, and the super-rare dot-segment displays found on some of the Limited Edition 18K Calculators (manufacturers unknown, but presumably one of the ones mentioned here). The Green Dress displays were done by Sanyo, and found their way into several other LED makes besides Pulsar.