Mad Catz light gun problems with THOTD2 and my discoveries so far

[Gocha]

Hello everyone, I recently got a second Mad Catz light gun for the Dreamcast, but noticed that this one does not work properly with The House of the Dead 2 while the first one I got works fine. The bad one does work with other games like confidential mission without problem.
Both guns are being used with the same games, same monitor, same cables, all parts and games are NTSC-U as far as I can tell.
When trying to use the bad one with The house of the Dead 2 I can sometimes calibrate the very first shot at the calibration screen when I turn the game on, but I can't finish the process.

If used close to the monitor at less than 50cm (about 20 inches) in game it registers the shots and can be used to play, but not at the calibration screen, not even while touching the screen.

Switching the ports makes no difference, the good one works in any port, the bad one doesn't work in any port.
There are no visible signs of damage outside or inside the light gun.

I found a few reddit posts about the same issue, light guns that work with other games but not properly with The House of the Dead 2 unless the brightness and/or contrast are way up.

Considering I have both a good one and a bad one from the same company and that both have 3 PCB boards inside I thought of opening both comparing the PCBs and switching the PCBs one by one so I could isolate the part that is giving problems.

I marked everything from each one so I didn’t mix the parts by mistake, “1” is the working one and “2” the one that is giving me problems.
As soon as I opened both and saw them side by side, I noticed that the board with the sensor was different in both guns.

The gun 1 has an integrated chip (LM359N) at its sensor board while 2 doesn’t and has 2 parts that look like transistors to me (S9014 C118). Switching the sensor board from gun 1 to gun 2 made gun 2 work, and using gun 2 sensor board on gun 1 made it so it has the same problem that gun 2 had before, so is safe to say that the problem is the sensor board. I didn’t find much of a difference in the rest of the gun anyway, the main board and the one with the buttons are very similar.


This is a comparison of the other side of the PCB

Since the problem is at the sensor PCB and it has an electrolytic capacitor, I thought that maybe a bad cap could be causing the problem (yeah, this is what people like me that doesn’t know much about electronics always try, I know), so I tried replacing it, but there is no difference in functionality, the gun with sensor board 2 still has the issue and the maximum working distance is the same.

I guess I could try replacing the sensor itself from gun to gun, but I’m a little afraid of breking it apart while trying, so besides that this is as far as I can get by myself considering I know little to nothing about integrated chips, so I wanted to ask you guys a few questions about it.

- What does the integrated chip LM359N does in here?
- Could it be possible to add the chip to gun 2 so it works as good as gun 1?
- Do you guys think is the chip difference or would you think is a sensor difference?

Any help would be appreciated, I know it’s a long post and I could just buy another one, but I really want to solve this since there have been a lot of people asking online with similar problems for the past 20 years and very little information around.

[megavolt85]

on board number 1, the optical sensor amplification is done on the LM359 operational amplifier, and on board number two, the amplification is done on two transistors.
I think there is no need to explain that the operational amplifier microcircuit provides better amplification than two transistors

[Gocha]

on board number 1, the optical sensor amplification is done on the LM359 operational amplifier, and on board number two, the amplification is done on two transistors.
I think there is no need to explain that the operational amplifier microcircuit provides better amplification than two transistors

I see, do you have any suggestions on how to amplify the signal so it is similar to the other board?

[megavolt85]

I see only one way out, you need to make your own board with an operational amplifier

[Gocha]

Hmmm... well, making my own PCB sounds a little too hard for my level, but I'll be trying it anyway just to check how hard is it.
One last question about the operational amplifier, if I was able to make the board would I need to do something to the chip before using it? or would it be ready to be use for this out of the factory?

[tmarvin]

I believe that IC would be ready from the factory. The product description will say programmable, but the operation is determined by the resistors connected to it.
You will need to obtain the correct resistors, too. Look for an SMD conversion calculator online to find the values. The ones labeled as "474" are 470 kOhms, for example.
I think you can get away with using the capacitors from the existing board. Just watch the polarity of the one large electrolytic cap.
Prototype through hole circuit boards are cheap and can be trimmed to size.

[Odyssey113]

Interesting post. One of my 2 guns started crapping out this week myself.

Just took the problem gun apart to compare it to your post, and my problem gun has the two transistor board as well.

I wonder if it's a voltage issue? Mine worked previously just fine.