Hi,
Many thanks for the pictures of your boards and the link for Who Dunnit prototype.
Your red board look to be, the very first prototype of WPC-95.
While used on a NGG sample, the blue board has the caracteristics of later serial production, not a prototype.
Indeed: on your red prototype board, the date of manufacture is inked : 36-95, meaning week 36 of 1995. That was the first week of september.
Our green prototype has been manufactured two weeks later : 38-95, and there is also a stamp on, showing SEP. 28, 1995. that is coherent.
The only difference is the funny "green" SIP Resistor network installed on your.
Strangely, they use a 9R instead of the 10R. But may be, this was caused by an error in the WPC-95 schematic...
On previous WPC-S, pin 1 and 10 goes to VCC. On WPC-95, the schematic say pin 1 to GND... and this is wrong (and illogical). Indeed, the wiring is the same as WPC-S, both pin 1 and 10 goes to VCC !!!
Note that, on your RED board, the watchdog is permanently deactivated, using a 0 ohm strap at J203. On our board, a switch was installed.
Your board has also been modified later: it had received the service bulletin 86 modification (the diode and the resistor added to avoid battery discharge). This modification was not in place on our green board.
The prototype boards may be easily identified, as they have some visual difference from the production(on picture, bellow) :
- Only one big chemical caps C31 is installed (the second, C77 is missing).
- Some caps (C74, C75, C76) had been added to filter the power lines arround the ASIC.
- An unmarked (may be R129) resistor had been installed (service bulletin 86 ?)
- Another R130 resistor had been added.
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