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Thread: Point Blank 1 & 2 Colours missing

  1. #1
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    Point Blank 1 & 2 Colours missing

    Hi all I finally just plugged in my PB1 & 2 pcbs and have noticed colours missing.
    PB1 is missing red
    PB2 is only showing green
    Now I know people will start mentioning about adjustments on CRT but the interesting thing is when I plug in my wonderboy and arpicade the colours are back to normal.
    I have tried the PB boards on my two different arcades and they do the same thing so I have definitely ruled out the CRT's.
    Before I received them @bwodie showed me photos and a video of the working with full colour.
    So, if this has happened during transit I do not know where to go from here. Any help would greatly appreciated, and if I have to go down the pcb repair road I will do that too if someone on here does it

    Thanks,
    Darren
    Attached Images Attached Images

  2. #2
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    As Darren mentioned, I tested them on my Sega Astrocity before sending out, and both were all good. What are the chances both boards could lose a colour like that??

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    I'd be cleaning the boards edge pins, and also double checking your cabinet connector that the pins grip firmly, and that you've lined it up correctly.

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    Way ahead of you @Holy-SNES I have already cleaned the board pins, but cabnet connectors are fine on both arcades and as stated ,these boards do the same colour incorrection on both cabs, but show full colour on my arpicade and wonderboy pcb's on both cabs..
    So I have narrowed down that is isn't jamma or cabs

  5. #5
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    Hmm, its just very strange that both boards are missing colours given that they were working recently. The odds of two working boards both contracting the exact same fault within a span of a week or so is extremely low.
    Have you tried plugging just the main board in without anything else connected (guns, I/O board etc)?

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    @Holy-SNES I certanly have, that is exactly what Bwodie has done too when testing to show me running pcb... This is a bizzare circumstance.... Hence the help inquiry

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    yeah when I tested I plugged just the PCB's in, nothing else. @Womble SOS ??!?

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    I know that Point blank 1 has some RAM in the output stages that are quite voltage sensitive ( over voltage sensitive ) , EG: anything over 5.20v and they seem to fail yet I have seen the same RAM on other boards of no value that I put up to 5.5v to test my theory and they seem to survive , so not really sure what it is that makes these same RAM fail on point blank but I have repaired a lot of them.
    In this case ignore what voltage your power supply showing , your only concern is the voltage on the board edge connector.

    The 3 RAM in question are marked in the pic attached, a quick test is to lick your finger and run it along the pins on each of these 3 IC's , if you see any colours flash up on the screen you have found the faulty RAM ( open circuit inputs or outputs ), They are SMD so don't attempt changing them if you don't know what you are doing.
    It's a been a few months since I did one so can't remember the part number but most likely 65256 ( 256K )
    PointBlank.pcb.jpg

  9. #9
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    Just to update everyone, the ram chip trick did not work, damn great idea though

  10. #10
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    Quote Originally Posted by Grimlock View Post
    Just to update everyone, the ram chip trick did not work, damn great idea though
    There are three SMD transistors (one for each color) in SOT-23 package used as final RGB output stage to bring video level to standard impedance.They are near the JAMMA edge, they are probaby faulty or missing.Replace them all.
    Caius on http://www.jammarcade.net

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