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Author Topic: SNES/Genesis Konami Justifier: how to determine photo diode/phototransistor?  (Read 274 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.