mert8431
New member
Note: I originally posted this on the technical video games repair by mistake. I couldn't move the post or delete it, so I created a new one. Sorry Mods.
Need some advice or a suggestion from someone on where to get a new MPU board or some tips.
So I just went to fire up my Bally Black Pyramid and instead of starting up like it normally does, I just got the general lights and nothing from the score read out or other lights. Checking the manual, I'm told to pop open the back box and check out the the LED light for status...
Flipped power switch on:
Light flashes 1 to confirm power and then flashes quickly 5 times and then LED goes off. It should flash 7 times for the game to start up properly. Game manual suggests removing J1, J2, J3, and powering up the game. Same deal. Pulling J4 gets no lights as this is the power to the board.
Checking the Bally repair manual it says for 5x flashing, check some ciruits and pins...I have to go get a multimeter tomorrow...
In the mean time, if a chip is dead is there a good place anyone can recommend to send it?
The MPU-A4 is a bally midway a084-91624-aa44
KI4SWY posted the following on the other thread:
Sixth Flash Completed*:
The Fakers Guide: a sixth flash means the PIA at U11 (6821) and the U12 timer (5550 chip is good. No sixth flash means either PIA U11 (6821) or its socket is bad, or the U12 (555) timer is bad. Lack of the 6th flash (five flashes only) can also mean a problems with the zero-crossing detector. Often this is the MPU board's R113 resistor (2k ohm, near the J4 connector) is open. This resistor takes the 43 volt DC coil power to the zero-crossing detector circuitry and normally runs hot. Hence it may eventually go open, so check it if only 5 flashes from the LED are seen. Thanks to Ray J. for this tip.
Techno Guide: The U9 CPU chip monitors PIA2, port CA1 (U11). If transitions from high to low are detected, the CPU decides the Display Interrupt Generator is working. If U12, a 555 timer, or any associated circuit component fails, the CPU will not flash the LED the sixth time.
I'm getting no 6th flash so it seems either the U9 or U11 could be issue...does anyone know where I could get them replaced?
Need some advice or a suggestion from someone on where to get a new MPU board or some tips.
So I just went to fire up my Bally Black Pyramid and instead of starting up like it normally does, I just got the general lights and nothing from the score read out or other lights. Checking the manual, I'm told to pop open the back box and check out the the LED light for status...
Flipped power switch on:
Light flashes 1 to confirm power and then flashes quickly 5 times and then LED goes off. It should flash 7 times for the game to start up properly. Game manual suggests removing J1, J2, J3, and powering up the game. Same deal. Pulling J4 gets no lights as this is the power to the board.
Checking the Bally repair manual it says for 5x flashing, check some ciruits and pins...I have to go get a multimeter tomorrow...
In the mean time, if a chip is dead is there a good place anyone can recommend to send it?
The MPU-A4 is a bally midway a084-91624-aa44
KI4SWY posted the following on the other thread:
Sixth Flash Completed*:
The Fakers Guide: a sixth flash means the PIA at U11 (6821) and the U12 timer (5550 chip is good. No sixth flash means either PIA U11 (6821) or its socket is bad, or the U12 (555) timer is bad. Lack of the 6th flash (five flashes only) can also mean a problems with the zero-crossing detector. Often this is the MPU board's R113 resistor (2k ohm, near the J4 connector) is open. This resistor takes the 43 volt DC coil power to the zero-crossing detector circuitry and normally runs hot. Hence it may eventually go open, so check it if only 5 flashes from the LED are seen. Thanks to Ray J. for this tip.
Techno Guide: The U9 CPU chip monitors PIA2, port CA1 (U11). If transitions from high to low are detected, the CPU decides the Display Interrupt Generator is working. If U12, a 555 timer, or any associated circuit component fails, the CPU will not flash the LED the sixth time.
I'm getting no 6th flash so it seems either the U9 or U11 could be issue...does anyone know where I could get them replaced?
