Yie Ar Kungfu Dead Arcade Board Repair

No booting, no video sync signal arcade board - Yie Ar Kungfu. Upon power on, the audio amp starts with a pop noise after 1-2 seconds. There is no video or video sync signal. The 68B09 CPU and some other chips do get warm. 5V and 12V are presented in the system.

It has clearly been reworked on. The GND plane and 5V rail copper has massive popping but tested have continuity.

SFX potentiometer was damaged.

Some ceramic capacitors have cracks.

PCB layer has strong delamination, but tested with good continuity.

Diagnosis

The CPU (6809EP) does have all DATA and ADDRESS pins working but seems stuck in a non maskable interrupt routine. With NMI=LOW, IRQ=HIGH,FIRQ=HIGH, MRDY=HIGH, RESET=HIGH, HALT=HIGH

The RGB signal connects to a Monolithic Memories PROM 6331-1. Given it’s small size I assume it’s a palette ROM so indexed colour goes in, and predefined RGB colour from this PROM to the display. The 5th bit of the address stuck high when the rest 4 bits stuck low. Since the video sync signal is missing, it’s understandable it will not read proper palette value.

Traced the video sync signal all the way to a 74LS367, where it keeps output HIGH. Then trace the input back to a “KONAMI” chip 11H, pin12 where it outputs a constant 1.3V.

Tried to swap two ROMs marked as “407 C09” “407 C08” from another board. The symptom is the same, no video sync. ROM issue is almost exonerated.

The repair

This board has a lot of logic IC working properly, at least in the VIDEO subsystem. I cleaned the socket and legs of 11H 12H and all sprite/tile ROMs from 14H to 17H. Video sync presents. Starts to output pictures with recognisable sprites. The SYS ROM 8D and 10D have similar problems, cleaned and reseated. Then it shows “RAM BAD”. Konami chip 16F pin 4 is receiving floaty values, so traced back to 14E (LS245) at least one of the channels is faulty. Piggyback a new LS245 can almost guarantee to show the screen “RAM 1 OK RAM 2 OK, ROM 1 OK, RAM 2 OK” then a grid static frame - a successful POST screen but no booting game though.

RAM transceivers 14F (LS245) and 14E (LS245) are both faulty, with some floaty channels. Socketed and replaced them. One of the main RAM’s (13F) existing socket is in poor condition, so that there are at least 2 legs cannot be seated properly. Consider replacing the socket.

After the RAM chips making good contact with the socket, the game boots with demo, without sound. Replaced RAM 13F socket.

10A (LS175) only has pin 10 output properly. Pin 7 and 14 are all ignoring input. That is probably why sound driver has seen address and data but never fired any signal to amp. 10A is faulty and needs replacement. (Without 10A, when the system issue a sound, it will crash the CPU and restart. Putting a LS174 with inverted legs lifted will stuck in reboot loop, possibly because pin 14 won’t drive 10B LS173’s /OC pin thus creating a data bus conflict. The previous non-working LS175’s pin 14 is constant HIGH)

Replaced 10A with new LS175 and VR1 with a generic potentiometer the music and sound came up.

Replaced VR1 with a proper potentiometer, with 1K range and the same footprint.

The board is now fully repaired.