defender stuck in BIOS?

zzaz3

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I just got all the parts to get my defender working. I plugged everything up and powered it on. I hear the bios sounds and see the jumbled screen like you normally would, but the screen just loops forever. It never goes to the game or to a gameover screen.

What do you think the problem is?
 
I just got all the parts to get my defender working. I plugged everything up and powered it on. I hear the bios sounds and see the jumbled screen like you normally would, but the screen just loops forever. It never goes to the game or to a gameover screen.

What do you think the problem is?

First thing to check would be the power supply voltages. Best place to check is on the RAM farthest from the power connector. This allows you to check all three voltages (+5, -5 and +12) all at the same time.

After that, you should check to see if the board is resetting (which it sounds like it is). To check that you'll need a logic probe and take a look at pin 37 on the CPU. If that is pulsing, then the game is resetting.

Check the Ribbon cable between the CPU board and ROM board (flex them or push down on the connectors) and see if you get a change.
 
I don't have a multimeter right now, but do you think the power supply could be broken? I'm using the original PS right now. The leds on the PS light up and the leds on the rom board light up for a second.

I have a new Power Supply from Bob Roberts that I need to setup. Do you think that will fix the problem?
 
The LEDs on the power supply just indicate the minimum voltages. You should always check the voltages on Williams power supplies at the ps board, the power input connector and some know chip location (like the RAM chips on the MPU boards and the Vcc of the ROM chips on the ROM board).

To help diagnose if it is a ROM issue or a RAM issue you can pull all the ROMS and add them back one at a time. The following link gives some info on how to do this (link).

ken
 
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