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Author Topic: SNES/Genesis Konami Justifier: how to determine photo diode/phototransistor?  (Read 2539 times)

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opt2not

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So I recently bought a Justifier for the SNES port of Lethal Enforcers from crashwg. It doesnít want to work properly. I didnít really expect it to given the price I paid. But Iíd like to see if I can repair it.

Right now, the shooting registers, but the shots seem to be off screen and not accurate. Sometimes I can get it to register on screen. But most of the time itís not hitting the screen, even when I put the tip of the gun right up to my CRT.

I suspect that the phototransistor in it has failed. But there arenít any markings or pcb labels that indicate what specific diode it is for a replacement.

Is there a way I can measure this to determine what replacemdntbpart to get?

Or, anyone have or know of the schematics for this part?


Titchgamer

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I am assuming you have already tried these things but just incase :p

Clean the lens and the ends of the sensors dirt can do weird things to light guns!

Also tried turning the brightness of the TV up a bit?

opt2not

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Yeah, I should have mentioned I tried that already.

Brightness up on the crt and in a dim room.
Opened up the lightgun and cleaned everything. Still the same result. Iíve read that these diodes donít last, so Iíd like to find a replacement if I can just get the right part number.

Titchgamer

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Yeah, I should have mentioned I tried that already.

Brightness up on the crt and in a dim room.
Opened up the lightgun and cleaned everything. Still the same result. Iíve read that these diodes donít last, so Iíd like to find a replacement if I can just get the right part number.

Figured you would of but had to check :p

Afraid I cant help with the Electronics side of things, But there is a Electronics forum (forgot name sorry) where the members are very good at ID'ing parts from pics so they may be able to help.

pbj

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Have you removed the part?  Probably has markings on the bottom of it...

This forum needs more threads about Arcade 1Up cabinets.

opt2not

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I'll try that next.

Unfortunately I'll have to remove the metal shielding first, but that's not a big deal with a good de-soldering iron.


pbj

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Dude... remove that shielding.  100% guaranteed that part is marked underneath it.

:bat
This forum needs more threads about Arcade 1Up cabinets.

AMG KC

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You dont want to turn the brightness up, you want that down. Its the contrast you want to turn up, and more so the blue colour, and this is what the gun will see.

I use a few different light guns on CRT projectors, and through a lot of testing, the biggest problems in order:

ē not enough blue drive
ē brightness too high ( washes out the screen )
ē green too low
ē red too bright

Using a CRT projector made it very easy to work out what the gun needs to see and what it does not.

ē covering red lens did nothing
ē covering green lens made the guns less likely to work at distance
ē covering blue lens the guns did not function AT ALL no matter how close to the screen you got.

Using a direct view set you may need to access service menus to raise blue drive, but usually just raising contrast and lowering brightness is fine.

I see it so often people say "turn up the brightness"... Why??? The brightness controls black level or cutoff, which has very little to do with the gun, it sees a white or blue flash, which is a full 100ire, and contrast is the setting that affects that.

opt2not

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You dont want to turn the brightness up, you want that down. Its the contrast you want to turn up, and more so the blue colour, and this is what the gun will see.

Right. Regardless, the gun isn't working with whatever the tv is set to.

Thanks for the bump, though it doesn't really help answer question on how to determine the photo diode/sensor.  Do you know of a way to find this out?

Dude... remove that shielding.  100% guaranteed that part is marked underneath it.

:bat

I removed the shielding. Didn't see any markings showing what the part is.
I didn't snap any photos, but I found an album of someone else's and as you can see it is unmarked:

https://imgur.com/a/KEAA0

Doing some googling, I found 3 parts that "look" like they could work as replacements, but I'm not sure by the specs which is best since I don't know how to determine the operational specs of the original one.

This one looks the closest, at a 2.7-5.5 VDC , 2 mA draw.
https://www.parallax.com/product/604-00084

Here are a couple more:
https://www.digikey.com/product-detail/en/ams/TSL235R-LF/TSL235-R-LF-ND/3095040

https://www.digikey.com/product-detail/en/ams/TSL237S-LF/TSL237-S-LF-ND/3095041


https://www.parallax.com/product/604-00084

pbj

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Buy 1 of each, start dropping them in, see what happens.

This forum needs more threads about Arcade 1Up cabinets.

AMG KC

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Yes i do, but without opening one up i cant tell, because they have no markings, and that makes it hard.

Whether or not the comments i made about brightness settings do help you or not, the fact remains it was said brightness should be up, and that is totally incorrect.

opt2not

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Yes i do, but without opening one up i cant tell, because they have no markings, and that makes it hard.

Whether or not the comments i made about brightness settings do help you or not, the fact remains it was said brightness should be up, and that is totally incorrect.

Thanks for the info.

Buy 1 of each, start dropping them in, see what happens.



Bah.  Alright fine.

Metalman1661

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Any update on this?

I am trying to fix a Genesis Justifier and I cannot find a suitable part number for replacement.


opt2not

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Nope. Sorry.
I moved to a house. All my junk is in boxes till we're done reno's. Even then, I won't be taking this on any time soon. Too many other projects I'm looking forward to do. 

But if you find a suitable replacement, let us know!  :cheers:

Zebra

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Why not just use one of the happ universal light gun sensor boards (the 4 wire version). Just solder the 3 sensor legs to the corresponding points on the happ board and mount the happ board inside the gun (using hot glue).

I have done that with three guncon 2 guns and one guncon 1 with three different models of time Crisis arcade sensor pcbs. Those photo diodes seem to be mostly universal. I have a lot and they all seem to run on either 3.3v or 5v.


opt2not

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Why not indeed.  :dunno

Zebra

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Yup, it's the way to go probably and, if the photo diode is not the issue, the caps on these guns also fail and one of the signs is unreliable registering or not registering at all. Changing out the sensor board should fix that too, as long as it still runs through the original i/o chip.

While you are at it, I recommend switching out the lens for a Konami arcade gun lens. The arcade lenses let through way more light and Konami arcade parts seem to fit their home guns. They use the same trigger and same size sensor board etc. At least my Terraburst arcade guns seem to fit Konami PS1 gun parts.

I suggest using shielded cable to connect the old sensor board to the new one and not making the wire any longer than is necessary, or you'll create other issues with accuracy.

opt2not

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I just remembered, I sold all of my lightguns before moving.
So itís information is good for others to do. Iím out.

Metalman1661

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Why not just use one of the happ universal light gun sensor boards (the 4 wire version). Just solder the 3 sensor legs to the corresponding points on the happ board and mount the happ board inside the gun (using hot glue).

I have done that with three guncon 2 guns and one guncon 1 with three different models of time Crisis arcade sensor pcbs. Those photo diodes seem to be mostly universal. I have a lot and they all seem to run on either 3.3v or 5v.

I'm sure this option would work. The problem is this universal Happ board is roughly the same price as the gun itself.

These Genesis/Snes Justifiers are only about $30. I was hoping I could figure out the part number of the existing phototransistor and possibly find a suitable alternative (assuming the exact part number is most likely obsolete). I did purchase some potential replacements from Digi-Key and dropped them in and they did not work (TSL235R-LF, TSL257-LF, BPW77NA).

Also the actual board the phototransistor is soldered to is very basic. It has just one resistor (1K ohm) and one ceramic capacitor (0.1 uF) . There are wires that run to the main logic board after that. The phototransistor is three legs so that limited my search for suitable alternatives but I am not sure on other details of how the transistor communicates to the logic board.

There is a reddit post showing the insides (except the logic board): https://www.reddit.com/r/crtgaming/comments/7n9qws/what_photodiode_or_phototransistor_did_the_konami/

Any insight you can provide is greatly appreciated.

Zebra

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You'll find the issue with most light gun problems is that the cost of replacement parts is often close to or equal to buying a whole new gun. There is no real way around that. Perhaps you should just get a new one.

You can find used sensor boards on ebay but even then, you have to ask if it's worth the effort:

https://www.ebay.com/itm/1-happ-gun-pcb-board-opto-ARCADE-VIDEO-GAME-PART-cf3-25/163884996987?hash=item26284e997b:g:JyMAAOSwYxxdkVF2

You could just buy a replacement photo diode from Betson but I'm not sure if they have a minimum order value:

https://www.betsonparts.com/amusement-redemption/arcade-guns/op805sl-photo-transistor-for-betson-imperial-shotgun.html

and, you don't really know if the photo diode is actually the issue. It could just as easily be the cap. Using a whole new board should solve most issues.