Thanks! I've drawn up a schematic (attached). It should be correct.Having opened up my Archimedes' mouse, the circuity looks surprisingly straightforward
As you say, it's quite simple so while some of the tracks around LD2/LQ2 aren't easy to spot, it was still easy to guess where these went, as there is no other logical choice as to where they must connect to.
The transistor and diode mystery are solved - Q1 and D1 etc make a constant-current driver for the IR LEDs for the rotary encoders.
The only thing I got confused by was the pinout for the IR LEDs, LD1 and LD2.
Starting with LD2, the center pin is connected to +5v, and other two pins paralleled together. I assumed then it must be a dual LED package with a common anode.
That made sense until I followed the track from those two pins into LD1, where the connections were completely different. If they were indeed a pair of paralleled LEDs with a common anode, then one of the LEDs in LD1 would be bypassed, and would never light. That makes no sense, of course.
The only logical conclusion I can come to is that one of the pins (I have called it Pin 1 in the schematic) must be a NC (no connect) pin simply for structural support of the component, and the LEDs are likely connected in series (or maybe parallel) internally, between the other two pins.
No configuration where Pin 1 has an electrical connection makes sense to me, considering the track layout.I think I got everything, but if you could confirm what Q1 and D1 have marked on them, as well as the value for the electrolytic capacitor C2, that would be nice for completeness sakeIf you need any individual tracks buzzed out, let me know.
I'm assuming the connections for D1, and that it's a dual 1N4148, but I can't read the number on it.
Q1 appears to read "1AM" which corresponds to the SMD version of a 2N3904.
C1 is probably 0.1uF. In any case, anything from 0.01uF to 0.22uF would likely work.
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Thanks for posting this I have loads of mice to check
Statistics: Posted by razz177 — Sun Mar 17, 2024 3:02 pm