Looks like 390 ohm 1%, the 377 would be a bit low but if you use an ohmmeter it might be closer (Should be 386-394 ohm to be in that 1% range)

After seeing your response, I got to work and already soldered in a new resistor. According to the multimeter, it's a 388-ohm, so it should be within the 1% range. I know my soldering job doesn't look the best, but I checked it with a multimeter, and it should be working. Unfortunately the fried resistor wasn't what caused the trackball to not work, and I'm back to square one. What else can you possibly check that could be failing? Also, what I noticed when going through the board with my multimeter is that none of the resistors were giving any resistance beside the one I soldered in (or maybe I had a wrong setting in the multimeter). I'm out of ideas.

Getting a burnt resistor on a mouse... I'm finding it hard to think of a way that with normal operation one could get a resistor burnt on a serial mouse.
anyway

Did you check the cable for continuity ?

I did not and I will do that tomorrow, thanks. Also I just noticed that I forgot to upload a photo of my soldering job... Mabye that's better becouse it looked absolutely terrible.

Here I am back again after checking the cable for continuity, and I didn't find anything wrong. I also decided to follow the traces on the trackball board, and I also couldn't find anything that could've caused the damage. Any ideas? Could it be the black chip that's damaged? There is no visible damage to any component .

What driver are you using?

The standard driver which comes with Windows 95. It works with every other COM mouse I have, even a Logitech CyberMan (look it up, the design is really interesting). Do I really need a specific driver the trackball?
The way I test it is:
1. Plug it in while the PC is turned off.
2. Boot up Windows 95 and add the mouse via the proper option in the control panel
3. Reboot

ksiumaxx wrote on 2025-06-02, 17:07:

The standard driver which comes with Windows 95. It works with every other COM mouse I have, even a Logitech CyberMan (look it u […]
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The standard driver which comes with Windows 95. It works with every other COM mouse I have, even a Logitech CyberMan (look it up, the design is really interesting). Do I really need a specific driver the trackball?
The way I test it is:
1. Plug it in while the PC is turned off.
2. Boot up Windows 95 and add the mouse via the proper option in the control panel
3. Reboot

I was only asking, wondering.

The chip seems generic enough that finding a sort of schematic online is easy.
since it's still not working, go a step further and draw a schematic.
The simple schematic I just looked at has way less transistors than what are visible on your photo.
and given the generic chip HM8350A, you could probably find the same one in another generic mouse from the same era.

Check diodes and transistor, be mindful that you usually have to take them out of the circuit for a proper measurement. Also the crystal might be bad, I've seen it before, seems to be a standard 32768Hz one but always check what's written on it. Strange that other resistors don't show any value because they should, please recheck.

I'm back again after testing the components with a multimeter. I don't remember the exact values they gave me, but most of them worked. Only one transistor wasn't giving any values, so I think that might be the problem, not sure though. I also took some pics of the board on both sides so y'all can see the schematic.

I also got writings from most of the components. All transistors on the board are C1815GR, the crystal thing had KDSIJ written on the side; the main black chip is a HM8350A 9240B, the capacitor is a 2.2uF 50V, and the long black thing (no idea what that is) had A 153G written on its side.
Another thing is that the resistors still didn't give me any values. I didn't take them out for testing, so that might be a problem, but then why would the one I soldered in show up on the multimeter?

Since the 390 ohm connects to Q7 and Q8, would suspect one or both Q8 and Q7 of shorted causing the R4 burn and then the one burned open...which transistor do you get no readings ?
Hmm odd you cannot get any readings from other resistors...getting a near perfect reading off the 390 makes sense if those tranny's are burned open...
update: corrected my text and added a rotated and mirrored of back...

FYI,
R1 & R2 & R5 look the same and should be 15 kilo ohm 5%. (brown green orange gold)

R3 looks like 3 mega ohm 5% (orange black green gold)

You not being able to measure any of the resistors makes me think you're doing measurement in diode / continuity mode and not in resistance mode.

The long black parts marked RP1 & RP2 are resistor arrays A 153G , seems to be an array of 15 kilo ohm resistors to one common pin. ie resistance measurement between pin 1 and all the other pins should give close to 15 kilo ohm, when measured out of circuit.

the 9042B on the chip is just a date code, possible meaning the chip was made in the 42nd week of 1990

Can you tell if any of the switches send data? I think R4 is to do with power to the rotary encoder LEDs, but I don't think that should affect the switches. I think the wire colours are Blue is Ground, Orange is -ve, Green in +ve, Brown is Tx, White looks like it's something to do with selecting MS Mouse mode. Might be worth checking which pins on the serial connector goes to which wire and check voltages.

So I'm back after 3 days of absence. I checked what you guys told me to do, but I didn't find any more stuff that might be broken or in need of replacement.

Horun wrote on 2025-06-03, 17:42:

Since the 390 ohm connects to Q7 and Q8, would suspect one or both Q8 and Q7 of shorted causing the R4 burn and then the one burned open...which transistor do you get no readings ?
Hmm odd you cannot get any readings from other resistors...getting a near perfect reading off the 390 makes sense if those tranny's are burned open...
update: corrected my text and added a rotated and mirrored of back...

The transistor I got no readings on is the Q1; in the picture I sent, it's the one which is hidden behind the cable. Checked it again and still got no readings.

weedeewee wrote on 2025-06-03, 20:51:

FYI, R1 & R2 & R5 look the same and should be 15 kilo ohm 5%. (brown green orange gold) […]
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FYI,
R1 & R2 & R5 look the same and should be 15 kilo ohm 5%. (brown green orange gold)

R3 looks like 3 mega ohm 5% (orange black green gold)

You not being able to measure any of the resistors makes me think you're doing measurement in diode / continuity mode and not in resistance mode.

The long black parts marked RP1 & RP2 are resistor arrays A 153G , seems to be an array of 15 kilo ohm resistors to one common pin. ie resistance measurement between pin 1 and all the other pins should give close to 15 kilo ohm, when measured out of circuit.

the 9042B on the chip is just a date code, possible meaning the chip was made in the 42nd week of 1990

Yeah, you were right about it. It was my fault that they weren't showing any resistance because I had the wrong setting in my multimeter. My mistake; as I said, I don't have much electrical knowledge, so it was to be expected. The 3 resistors you mentioned are all somewhat 15k, but only one showed exactly 15 kilohms. The other 2 were close but not exactly it. However, I wasn't able to get any reading from the R3 resistor. No idea why. I tried every setting; it just wouldn't show up.

snufkin wrote on 2025-06-04, 20:45:

Can you tell if any of the switches send data? I think R4 is to do with power to the rotary encoder LEDs, but I don't think that should affect the switches. I think the wire colours are Blue is Ground, Orange is -ve, Green in +ve, Brown is Tx, White looks like it's something to do with selecting MS Mouse mode. Might be worth checking which pins on the serial connector goes to which wire and check voltages.

I don't know how to check that. I checked if the trackball's buttons work because I was thinking that only the moving part wasn't working, but no. The entire device seems dead and not detected by the computer. I did check the cable again, and pin 3 of the DB9 connector is the brown wire, pin 4 is orange, pin 5 is green, pin 6 is blue and pin 7 is white. I don't know if the wiring is correct and compatible with the standard COM mouse wiring.

I guess you could try measuring if the chip gets any voltage by setting the multimeter to voltage and the probes on pin 9 & pin 18 , with the mouse connected to the computer.

if you're looking at the chip, with the notch facing upwards pin 9 is the one on bottom left and pin 18 is the one on top right.

I checked the voltage and the chip is getting some. I have no idea if the multimeter is set correctly but I got a reading of 6V between the pins you mentioned.

ksiumaxx wrote on 2025-06-07, 13:02:

I checked the voltage and the chip is getting some. I have no idea if the multimeter is set correctly but I got a reading of 6V between the pins you mentioned.

That should be enough.

ksiumaxx wrote on 2025-06-06, 14:34:

snufkin wrote on 2025-06-04, 20:45:

Can you tell if any of the switches send data? I think R4 is to do with power to the rotary encoder LEDs, but I don't think that should affect the switches. I think the wire colours are Blue is Ground, Orange is -ve, Green in +ve, Brown is Tx, White looks like it's something to do with selecting MS Mouse mode. Might be worth checking which pins on the serial connector goes to which wire and check voltages.

I don't know how to check that. I checked if the trackball's buttons work because I was thinking that only the moving part wasn't working, but no. The entire device seems dead and not detected by the computer. I did check the cable again, and pin 3 of the DB9 connector is the brown wire, pin 4 is orange, pin 5 is green, pin 6 is blue and pin 7 is white. I don't know if the wiring is correct and compatible with the standard COM mouse wiring.

Can you post a picture showing which wires are on which pins? I was expecting something connected to pin 2 which I think is the Rx pin for the computer. If there's nothing connected to pin 2 then maybe this isn't a serial mouse?

[edit: Ah, is it a 25 pin connector? Anything connect to pin 2 or 20?]
[and now I see the first picture and see that it is a 9 pin. Other pictures online shows a 25 pin. So, is anything connected to pin 2?]