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Thread: Donkey Kong TKG4 Repair Logs

  1. #11
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    Bloody awesome effort. Well done.
    This is where it ends!

  2. #12
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    Quote Originally Posted by Kaizen View Post
    CPU Board
    Fault: Garbled graphics

    This was a relatively easy one, the game would boot to garbled graphics and run for a few seconds then freeze.



    I started looking around the CPU area
    and found the outputs coming from the 74LS74 at 7F were all dead.

    https://i.imgur.com/Qoo7Wri.jpg

    The chip was removed and replaced and the board now boots up and plays normally.



    CPU Board
    Faults: Wouldn't sync - Only green colour - Missing Kong thump sound - no 'Up' input from the joystick

    The board had copped a decent hit at some stage and there were two transistors, a number of resistors and a cap missing/damaged on the final video stage.

    https://i.imgur.com/N9Frnig.jpg

    These were all replaced and the colours and sync were restored.

    Right near the edge connector, the board had had an impact and the 'Up" input signal trace had been cut. A resistor leg was inserted into the via, laid over the broken trace and soldered in place.

    https://i.imgur.com/cjGcNE5.jpg

    To check the pounding noise that Kong makes at the start of the game when knocking down the girders, you can short the Collector to the Base of Q2 (or touch the base with a logic probe) and you should hear the noise, when I did this there was nothing. I checked the transistors and caps which were all good. I followed the base of Q2 back to the 74LS161 at 3J and found pin 12 was stuck low.

    https://i.imgur.com/IAk7yOY.jpg

    After replacing it the Thump sound was restored.

    The board is now fully working.


    CPU Board
    Fault: Boots then screen goes blank




    This board would boot up then withing a few seconds the screen would go blank.
    I checked the reset line which was good and worked my way down the left side of the board and when checking the 74LS139 at 2A, the outputs were toggling.

    https://i.imgur.com/Luio3ev.jpg

    Replacing it fixed the issue and the board is now fully working.
    Hey. I think I have chased down the same problem on my board so I will be looking at the equivalent LS139 chip on my board tomorrow (2C instead of 2A). The outputs should be pulsing right??

  3. #13
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    Quote Originally Posted by hvc01 View Post
    Hey. I think I have chased down the same problem on my board so I will be looking at the equivalent LS139 chip on my board tomorrow (2C instead of 2A). The outputs should be pulsing right??
    What's pin 1 doing?
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  4. #14
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    Quote Originally Posted by Kaizen View Post
    What's pin 1 doing?
    all pulsing apart from grounded pin. i then checked 4H (TKG4 4D) and inputs pulsing but output pins 12,13,14 stuck high. replaced. no change. time for bed now.

    i would next be going to 8F and 7F to check here.

  5. #15
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    Video Board
    Fault - Graphics Glitch Above The Top Ladder




    The glitch only appears on the barrel screen when the sprites are moving.

    I've had this issue on a couple of boards and turning the voltage up reduces it but it won't go away until the +5v is at 5.25 volts (not good for TTL chips) and -5v is around -5.00 volts (usually sits around -4.74 when +5v is at 5.00volts).
    Initially I though it was related to the voltage drop between the two layers and later thought it might be related to the ECL chips but swapping them out on one of the boards made no difference.
    I'd spent a few hours on this issue and it was doing my head in.
    I put it in the too hard bin for a few months and decided to take another look at it tonight.

    After going over the ECL chips again with no luck I decided to go for a random walk around the board with the logic probe and see if I could spot anything that didn't look right.
    I checked all the lower order TTL chips and all looked good then I came to the 74LS373 Transparent Latch at 3K and started to look at the inputs/outputs and when I touched pin 18 with the logic probe I found the glitch would disappear.
    I pulled the chip and it tested okay, 3K was then socketed and and I put a new chip in with no change.
    I had a similar thing happen on a Pong board where the capacitance of the probe (or my finger) was enough to fix the issue.

    Putting the original chip back in and adding a 22pF ceramic cap across pin 18 and ground fixed the issue (piggybacking it with another 74LS373 also made it disappear).
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

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