Hardware test program for Genesis Justifier, Menacer and\or ALG GAMEGUN?

[nintendo2600]

Hello,

Does anyone here know of or have a test program to check the functionality of
Sega Genesis lightguns? I've looked around quickly on google but didn't
really find what I was looking for. Just something that can read what
is or isn't working on a lightgun be it the Menacer or Justifier flavor.
Specifically I'm going to be testing an American Laser Games GAMEGUN
which is both a Menacer and Justifier in one.

Thanks!

[lidnariq]

I couldn't trivially find any useful documentation about how the Justifier and Menacer worked, so had to look at BizHawk's source, where they say:

Menacer:
Down on normal pad ↔ back trigger (patent calls this "SW3")
Right on normal pad ↔ pause button (lower front trigger; "SW1")
Up? or Left? button on normal pad ↔ upper front trigger ("SW2")
Left? or Up? button on normal pad ↔ center front trigger ("SW4")
TH input ↔ low during instant Light
Usually uses hardware inside Genesis capture falling edge of TH to convert to coordinates

The 6-in-1 pack-in game has a calibration screen you could use for this.

Justifier:
Down button on normal pad ↔ trigger
Right on normal pad ↔ start button (side)
TH input ↔ becomes low when light
TR used as output to select between two guns

Not really clear why they're incompatible.

[nintendo2600]

I'm starting to think the gun itself is not working. Are you familiar with the ALG gamegun at all? I've opened it up
and I see a good amount of flux crust and possibly corrosion from the large resistor (or is this a color coded capasisitor?).

LE 1 and 2 only register the trigger in menu, neither game sees the sensor on screen or the start button. Menacer 6 in 1 doesn't register
the trigger or the start button and unless it moves the cursor on its own per chance, the photo diode isn't registering the aim on the screen
either. I'm using a CRT that I use for all my gun games and even cranked the brightness just to make sure it wasn't that and it
wasn't. I've checked the start button, trigger switch and the DB9 cord for continuity and they are each good. If I've attached pics of the PCB.

DSCF0305.JPG (114.27 KiB) Viewed 7591 times

[lidnariq]

... I think I agree that that color of blue-green implies capacitor? But I'm really not confident.

There's nothing particularly complicated on that PCB. I think you're right that it's probably the phototransistor (metal can, letters "E" and "C" adjacent). What test tools, if any, do you have?

[nintendo2600]

I have a digital multimeter but that is about it.

EDIT: The color code is Silver(grey?)\red\blue\green\Silver.

The photo transistor is a motorola MRD310 with the 3rd leg removed.

[lidnariq]

Does your multimeter have a frequency test? If so, what does it say the frequency across the phototransistor is when you're pointing at a white screen?

[nintendo2600]

Does your multimeter have a frequency test? If so, what does it say the frequency across the phototransistor is when you're pointing at a white screen?

I'll have to check to see if it does. I've never used it to do something like that before but that is a pretty clever method of testing I have to say

[nintendo2600]

I hope there is some equal to the MRD310 if that does turn out to be the problem. I've googled it and digikey doesn't have them while amazon and ebay want at least $30 for 1! Some guy is selling a pack of 10 for $99. I'm so used to getting them 5 for a dollar with replacing the photo diodes\resistors on other systems like the Atari or Nintendo. I've not replaced one in one of these Sega Genesis guns like this before, never in this exact model for sure. I think I recall refurbing a Justifier years ago but I would have remembered if I paid out the wazzoo for the photo senor which I don't. That or I blocked it out on purpose

[nintendo2600]

I'll see about the test with the multimeter tomorrow and report my finding then. Thanks for your help in this matter.

[lidnariq]

MRD310 should be something you could replace with any phototransistor of comparable specs, i.e.
dark current around 5nA at room temperature - this is unusually low
3.5mA at 5mW/cm² 2870K blackbody
0.8mA at 0.5mw/cm² 940nm IR LED
2µs rise time
2.5µs fall time

Vishay's VEMT2500 series looks comparable - a little more IR centered (~830nm vs 800nm), although SMD.

[nintendo2600]

MRD310 should be something you could replace with any phototransistor of comparable specs, i.e.
dark current around 5nA at room temperature - this is unusually low
3.5mA at 5mW/cm² 2870K blackbody
0.8mA at 0.5mw/cm² 940nm IR LED
2µs rise time
2.5µs fall time

Vishay's VEMT2500 series looks comparable - a little more IR centered (~830nm vs 800nm), although SMD.

I'd like to stay with a through hole if possible but I'm thankful to hear there is alternatives. Also, reading
this as a colored coded capacitor (I'm pretty sure it's a cap) it should be an 82 uF ±5% right? Just figuring
out what I'm gonna need just in case I repopulate the whole PCB as new.

[TmEE]

Usually green parts with such shape are inductors.

[nintendo2600]

Usually green parts with such shape are inductors.

Thanks for that info. Do you know where to buy them by chance? Ebay has nothing that matches.

The photo transistor is kinda interesting how it's set up. The emitter and collector are attached but the base isn't attached to anything.

My multimeter doesn't seem to be able to do feq testing. It's just a simple "tack life" unit that is only able to do resistance, continuity, voltage and diode testing.

EDIT: Using the ohm setting I was able to measure that the inductor is good. Also measured the photo transitor pointed at a light and then away from it and it does respond. On the 2k max setting it shows in the light to register varying from .100 to .125 and of course back to flat reading when in the dark. The inductor on the 200ohm max setting reads at 66.3 which I believe shows it's good if it actually is an inductor.

[lidnariq]

The photo transistor is kinda interesting how it's set up. The emitter and collector are attached but the base isn't attached to anything.

That's typical for phototransistors. They're "real" transistors, with all three standard pins, but they're explicitly exposed to light instead of isolated. Photons landing on it produce a virtual base current, allow current to flow from collector to emitter.

Some designs may bias the Base with a fixed voltage ahead of time to get different performance, but usually it doesn't matter.

My multimeter doesn't seem to be able to do freq testing.

In hindsight, a better plan is to power the gun, measure the voltage across the phototransistor, and shine a bright light into it. You should see the voltage drop when the light is present.

[nintendo2600]

The photo transistor is kinda interesting how it's set up. The emitter and collector are attached but the base isn't attached to anything.

That's typical for phototransistors. They're "real" transistors, with all three standard pins, but they're explicitly exposed to light instead of isolated. Photons landing on it produce a virtual base current, allow current to flow from collector to emitter.

Some designs may bias the Base with a fixed voltage ahead of time to get different performance, but usually it doesn't matter.

My multimeter doesn't seem to be able to do freq testing.

In hindsight, a better plan is to power the gun, measure the voltage across the phototransistor, and shine a bright light into it. You should see the voltage drop when the light is present.

I edited my post above while you where posting to add more info.