This joystick is from the 1989-1991 era of Macs and is compatible with a wide range of macs including the Mac SE, SE/30, Classic, Powerbook 180, etc. Variants were also made for Atari ST and Amiga around the same time period.
It connects with a DIN9 cable to a programmable unit equipped with an EEPROM that can be flashed with its software - this gives it control over the detected dead null zones of the stick when it's close to its center, whether it's in direct position or in vector movement mode. The unit (called GMPU) finally sends a signal over to the Macintosh through an ADB cable (Apple Desktop Bus, which was the standard for other peripherals such as keyboard and mice).
The problem: The stick seems to be doing absolutely nothing while the buttons work perfectly fine. However, as I found out, the stick movement *does* mess with the signal just a tiny bit, but not enough.
GMPU board:
underside:
Next up, the interior of the joystick is fairly simple. The mechanical assembly deals with the x and y movement of the stick like so (view underneath):
The rotated cylindrical chambers look like so on the other side:
Their purpose is to rotate a thin film of many alternating masks (█ █ █ █ █ █ █ █ █ █) between the rectangular grooves shown in the above image. The components that go into these grooves are key to detecting the joystick movement, as shown on this little board (part of the joystick itself):
its underside:
As you can see, both axes have 2 pairs of DEL+photocell. The circular stripped film goes between the D's and Q's to mess with the detected curren before it's sent in some form to the GMPU shown at the start of this post.
Here's a closeup on those pairs, there are no markings so identifying them is hard for me:
Here's a video that shows the thin film as I rotate it manually and slowly:
Potential things to test:
1) are the DELs dead? If they work in infrared, I can't see it under a cellphone video shooting, but I haven't tried it in pitch darkness yet
2) are the photocells dead? I have no idea if these components are fragile/sensitive/time limited. However, as you'll see below, something does happen when I try to manually trigger them
3) are the potentiometers broken/misaligned - my lack of experience in electronics (I'm a physics teacher and never really delved in the wonderful world of electronics much, except this year)
4) bad solder joints - though I've tested most traces everywhere and I didn't detect anything bad
5) something else that would pop up for you based on the pictures
Here's a video that helps at least understand that the circuit works as intended, but not as much as intended. I pass a corner of a piece of paper between the DEL-photocells pairs and I can get a tiny bit of mouse movement (joystick acts as a mouse by default, even if there are no software driver)
Last note: I checked the voltage under a multimeter at the last step, when the GMPU sends out the ADB signal to the computer. The red wire is stable at 5.02 V while the black one, responsible for ADB signals is at 4.51 V. Wiggling the stick wildly would sometimes bring it up to 4.52 V, not always.
It connects with a DIN9 cable to a programmable unit equipped with an EEPROM that can be flashed with its software - this gives it control over the detected dead null zones of the stick when it's close to its center, whether it's in direct position or in vector movement mode. The unit (called GMPU) finally sends a signal over to the Macintosh through an ADB cable (Apple Desktop Bus, which was the standard for other peripherals such as keyboard and mice).
The problem: The stick seems to be doing absolutely nothing while the buttons work perfectly fine. However, as I found out, the stick movement *does* mess with the signal just a tiny bit, but not enough.
GMPU board:
underside:
Next up, the interior of the joystick is fairly simple. The mechanical assembly deals with the x and y movement of the stick like so (view underneath):
The rotated cylindrical chambers look like so on the other side:
Their purpose is to rotate a thin film of many alternating masks (█ █ █ █ █ █ █ █ █ █) between the rectangular grooves shown in the above image. The components that go into these grooves are key to detecting the joystick movement, as shown on this little board (part of the joystick itself):
its underside:
As you can see, both axes have 2 pairs of DEL+photocell. The circular stripped film goes between the D's and Q's to mess with the detected curren before it's sent in some form to the GMPU shown at the start of this post.
Here's a closeup on those pairs, there are no markings so identifying them is hard for me:
Here's a video that shows the thin film as I rotate it manually and slowly:
Potential things to test:
1) are the DELs dead? If they work in infrared, I can't see it under a cellphone video shooting, but I haven't tried it in pitch darkness yet
2) are the photocells dead? I have no idea if these components are fragile/sensitive/time limited. However, as you'll see below, something does happen when I try to manually trigger them
3) are the potentiometers broken/misaligned - my lack of experience in electronics (I'm a physics teacher and never really delved in the wonderful world of electronics much, except this year)
4) bad solder joints - though I've tested most traces everywhere and I didn't detect anything bad
5) something else that would pop up for you based on the pictures
Here's a video that helps at least understand that the circuit works as intended, but not as much as intended. I pass a corner of a piece of paper between the DEL-photocells pairs and I can get a tiny bit of mouse movement (joystick acts as a mouse by default, even if there are no software driver)
Last note: I checked the voltage under a multimeter at the last step, when the GMPU sends out the ADB signal to the computer. The red wire is stable at 5.02 V while the black one, responsible for ADB signals is at 4.51 V. Wiggling the stick wildly would sometimes bring it up to 4.52 V, not always.
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