Defender will not boot !!!

oppolo

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Wondering where do I start troubleshooting my Defender? From my research it's a later CPU board. It has a power supply switcher mod installed. And a battery mod on the cpu board. On start up the Defender makes the start up sound and on the rom board the four leds light all together and then go off. The monitor displays vertical bars and that's it.
What should I check from here?

Here's a link to the video.
http://s1008.beta.photobucket.com/user/oppolo_album/media/HDV_0085.mp4.html
 
Coining up doesn't do anything. Monitor tested working with another game.
 
Start by checking the power supply.

Check at the supply, note your voltages.

Now check at the PCB, (on the board, not on the connector), and note any voltage drop.

Good job getting the monitor question answered - it takes it out of the equation.

After the above troubleshooting is done, you could clean the pins and connectors. If your game is in a damp basement, they can corrode, cause a voltage drop, and result in problems.
 
Since the ram is furthest from the power input on the CPU board I'll check the voltage there and report back.
 
OK voltages at the furthest from the power for the 4116's are 12.02vdc, 5.01vdc and -5.06vdc.
What next?????
 
OK voltages at the furthest from the power for the 4116's are 12.02vdc, 5.01vdc and -5.06vdc.
What next?????

The voltages look pretty good. I would pull out the logic probe and check pin 37 on the 6809 CPU chip on the MPU board. It should be reading solid HIGH. My guess is that it is pulsing.

Vertical jailbars like that are usually an indication that the CPU is not running and the watchdog is resetting the CPU continually.

There are a bunch of possible causes for this on Defender boards. My first suspects are usually the 7474 chips. You need to check each one and make sure the Q & !Q pins are pulsing.

Another good source for helping diagnose issues is the trobleshooting guide here: http://arcarc.xmission.com/PDF_Arcade_Williams/Defender_Recap_CPU_Part_1.pdf

It will walk you through most of the steps in finding how to bring a Dfender back to life.

ken
 
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