TKG3-07 Donkey Board repair log for Jake 13

smalltownguy2

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Forum member Jake13 sent me his DK 4 board set for repair.

Here's what the board does during game play. Ignore the blue screen, the brightness is turned up too high on my Sanyo.



I have determined the problem lies on the clock board. eproms check out fine. Board acts the same way with different eproms plugged in. Swapped ribbon cables, no change. Swapped clock board to another working 4 board set, and the problem follows.

Where to start?
 
Forum member Jake13 sent me his DK 4 board set for repair.

Here's what the board does during game play. Ignore the blue screen, the brightness is turned up too high on my Sanyo.



I have determined the problem lies on the clock board. eproms check out fine. Board acts the same way with different eproms plugged in. Swapped ribbon cables, no change. Swapped clock board to another working 4 board set, and the problem follows.

Where to start?

A pic of the board and I can help more better as I don't own one of them yet. This is where an oscilliscope would be of great help. Start with any crystals you see and follow to the chips probe the inputs and outputs to see what is working and not working. Ram chips also need the clock signals so check them also.
 
Get schematics.. If it is a clock problem make sure if you replace 74sxxx chips don't replace them with 74lsxxx chips as the s chips have faster response and that can screw with thec lock circuits if you replace them with the slower 74ls versions...
 
Stolen from mikesacrade.com repair logs.
http://www.mikesarcade.com/arcade/repairs/dkong.html

Problem: Picture takes several seconds to sync, and characters are broken up in slivers, sections are up or down from where they should be.

Normally this is a 74LS163 at either 3E of 4E on the video board, but replacing both of these chips did not change the problem. I noticed if I press on the section of the board with these chips, the picture would somewhat fix itself. Running my fingers on the bottom of the MC10105 at 1F on the video board would really mess up the characters even more than they were. Replacing the chip fixed both the slow sync up and the characters.

Solution: Replaced faulty MC10105 at 1F on the video board.

Good luck in your repairs.
 
Stolen from mikesacrade.com repair logs.
http://www.mikesarcade.com/arcade/repairs/dkong.html

Problem: Picture takes several seconds to sync, and characters are broken up in slivers, sections are up or down from where they should be.

Normally this is a 74LS163 at either 3E of 4E on the video board, but replacing both of these chips did not change the problem. I noticed if I press on the section of the board with these chips, the picture would somewhat fix itself. Running my fingers on the bottom of the MC10105 at 1F on the video board would really mess up the characters even more than they were. Replacing the chip fixed both the slow sync up and the characters.

Solution: Replaced faulty MC10105 at 1F on the video board.

Good luck in your repairs.

I found that on Mike's page too. Problem is, the video board hasn't changed. Removing the CLK board from the set fixes the problem, so the problem is most definitely with the CLK board.

I'm going to get my hands on a few spare chips, and start piggybacking until I find one that changes the board's behavior.
 
Decided to take a low tech approach to this repair, since I don't have a logic chip analyzer.

I'm mapping the entire clock board, and hitting every pin on every chip on a working board with a logic probe. Once I know what every pin should be doing, I can go back to the non working board and see which chips are acting differently. Hopefully that will help me narrow down the problem chip(s).

Row 1 checks out fine. 3 rows to go.
 
Okay, decided to probe the entire clock board to see what's going on.

Found that chip 4H, labled SN74LS163AN, pin 2 has strange behavior. My probe tones match the static I see on the board. Every time the board exhibits the jittery or static behavior, the tone on pin 2 reflects it. You can hear the static on several other pins on that chip too.

Looks like that LS163 is some kind of counterdivider chip in the sync circuit, maybe?

Now the question is, do I see that activity because of that chip, or because of one upstream/downstream from it?

Made a quick video.

 
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Smalltownguy,

If you are in need of an additional untested TKG3-07-CLK board... I have one for ya... Given it does have the words "Bad Board" written on it, but that could be because it is missing ePROMs and H-pos/V-pos. I don't know. But just wanted to offer it to ya if you needed it. PM me if needed
 
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Bump - I'll probably be working on this board this weekend, since my new Hakko 808 has arrived. Makes pulling IC's for testing much easier.
 
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