Thanks, man!

Just taking a break.

This was a year ago. Miss your video's man! Hope you're okay.

Don't exactly know what you are measuring. A transistor must always be measured in 6 directions: B to E, E to B, B to C, C to B, C to E and E to C.
2 directions must have 0.4 to 0.7 (forwarding voltage) and one must be the added value of those 2 measurements (0.8 to 1.4). Preferably the transistor must be removed but the measurement can be a good indication of what is going on.

Another tip: if the value of your measurement is running higher and higher this indicates that a capacitor is in that circuit.

So, do a capkit, swap that HOT.

Is it possible to post a picture of the schematics you are using?

You must set your multimeter to diode testing. Normal resistor testing tests with too low voltage rendering your measurements invalid.

I love the current format. Don't listen to this awful man John 

You're missing the green color in your monitor. Can be the connection to that monitor which is causing the issue (jamma), but more likely a transistor on your neckboard died.(Vic already mentioned that).

Just to get some experience on board repair. I got this board for 20 euro (23 dollar).

Thanks Ian for your quick reply. I was afraif of that I must say, even don't know if the roms can be found.

Will dive into it, most of the ic's are TTL so troubleshooting must be doable.

Hey you guys, we are in the........ damn, that's John's line.

Whatever, i need your help with something. I just bought an el-cheapo Ms Pacman bootleg board. I knew it was defective, the guy who sold it said that the board was booting, showed some pacmans on the screen and then reboots. Having watched almost all the vids on the one circuit channel (thanks Adam!!) this might lead to the conclusion there is something wrong with circuit which is driving the watchdog.
So far so good. I do repairs on MPU boards from pinball machines and i want to dive into arcade PCB repairs, that's the main reason i bought this bootleg board.

After searching the internet for schematics of this board i came up empty. Is there someone who by chance has got this schematic???

This is the board (a simular one)

Got this one:

http://nl.aliexpress.com/item/High-Speed-TL866CS-Programmer-USB-EPROM-EEPROM-FLASH-BIOS-AVR-AL-PIC/32479845822.html?spm=2114.48010208.4.6.ttSaBC

Only use it for programming pinball eproms from 2716 to 27c040. Don't know what DK uses.

Look up grounding each color pin on the back of the neckboard as you can isolate/display each RGB color for the monitor.


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First find out where the problem is situated. You can easily swap the blue and red feeding into the monitor. Now blue gone -> board. Red still gone -> monitor.

Good luck!

When character rom 5e is removed game plays but maze is missing
When character rom 5f is removed game plays but pacman and ghost monsters are blocks of color.

Because of the fact that both the maze and pac are fucked up i guess the addressing is wrong on both proms. Get a logic probe en check all address and data lines on 5e and 5f. Is a line stuck on 0 or 1 or maybe floating?
Another thing to try: remove 5e, is PAC and his friends okay now? Reseat 5e, remove 5f, is the maze okay now?

Another tip to check the roms: put them in an eprom reader and feed the roms to mame. If you got the same issue in mame you know that rom is bad.

Buy an eprom reader from ali express. Those things cost 33 dollars and can be a huge help troubleshooting these kind of issues. If you find the proms to be okay you can search for an alternative cause of your problem. While you're at it buy a logic probe.

Then watch the episodes of onecircuit's repair on pcb repairs, and to 101 logic episode. There you will find all the info you need.

Ian is correct, the program is running so leave those proms be where they are. I think one adress line is pulled to 1 or 0. What you see on the screen is that each sprite is displayed twice, half of the sprite. Like the MSB (most significant bit) is tight to either 0 or 1. This tells me the sprite roms are okay, but the addressing is causing the issue.

Good luck man!

This issue is caused by the sprite roms. Put them in an eprom reader and verify them with the ones from mame. I guess that fixes your problem.

You +5 is way to low and this will cause problems, especially with the ram.

That +5 is from another board member, another (working) defender board.