Defender repair help.

DarkWolf896

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I bought a defender from a friend a few days ago. It didn't work the 4700mfd cap on the PS
was loose from the board. I replace it and the 5 other ones in front. as well as the 3 radial ones on the cpu board. I still wasn't getting anything so I removed the cpu board and examined the chips. the 7474 were so corroded when I tried to remove them, the pins snapped off. so I replaced the sockets and chips, and now it plays the start up sound. but the monitor shows wight with lines on it and nothing else. I also checked the voltages from the ps, 5v regulated read as 5.14v, -5v read as -5.12v, 12 unregulated read as 12.84v, 12v regulated read as 11.75v. this is my first time working on an arcade machine so I'm kind of lost...

Video of problem: http://www.youtube.com/watch?v=o60BO82OcmY
 
they just blink once, all on for a few seconds and then off. and sometimes all four stay lit
 
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I'd go after the ROM chips next. I had similiar symptoms on mine
and Replacing the rom chips from a different board did the trick.

Do you have a eeprom reader? Maybe checksum them all to see
if they are working?

Malice95
 
no I don't have an eeprom reader. I'll try to remove them clean the pins and reset the chips. most of the chips I have tried to remove wont come out there stuck in there pretty good.edit I used an IC puller to remove the chips the first chip I tried snapped off 2 pins these are so corroded.
 
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It looks like you have a monitor problem for starters - there appears to be a diag message there but you can't read it since the screen is messed up. To adjust the monitor, you need a small plastic screwdriver, and you need to be really careful as there's enough voltage in a monitor to zap you into next week. Keeping one hand in your pocket is good practice when doing monitor work. Defender should have a G07, look at the pic here and try adjusting the Horizontal Frequency:
http://www.therealbobroberts.net/go7-1.html#vcg07

Since you have no batteries, the game won't boot all the way up by default. It'll boot to the audit menu if everything else is working properly.
 
now it just has a white screen with a slow moving black bar. no message. but an occasional fleck of pink or some other color.
the rom chip with the pins broke off is working the pins were still in the socket so I just reinserted it and they made contact. I need to replace it but for now it works.(the rom solution not the machine.)
 
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It looks like you have a monitor problem for starters - there appears to be a diag message there but you can't read it since the screen is messed up.

Since you have no batteries, the game won't boot all the way up by default. It'll boot to the audit menu if everything else is working properly.

Along the lines of what AMG is saying....

Can you press the ADVANCE button inside the coin door and get it to play blind? (sounds but no image)

I would check the video cable going to the monitor and make sure it's secure.

Everything else "sounds" normal so far from what I see in the video.
 
Without batteries it takes more than coin up and start to try and play blind. Since the cmos will be erased, the machine (if working) boots into audit mode. To get from audit mode to game over you hit (this is from memory) manual down, advance, auto up, advance. That backs you up to setting 28 "Special Function", then forward from there to exit audit mode. Then you can try to coin up and hit start. Check the voltages right at the corners of the ram chips on the cpu board - you can have good voltages at the PS but lose some with bad wiring/connectors/solder joints/etc.
 
I checked the voltage at the ram. -5v=-5.22v/12v=11.66v/5v=5.12v
after re seating the ram and fixing a few solder points. all I get is a black screen now. It still plays the start up sound, but still cannot blind play. I think it might be the 12mhz crystal it looked pretty bad when I got it. I cleaned it up a bit.

Image: http://img816.imageshack.us/f/cam0306.jpg/
 
I checked the voltage at the ram. -5v=-5.22v/12v=11.66v/5v=5.12v
after re seating the ram and fixing a few solder points. all I get is a black screen now. It still plays the start up sound, but still cannot blind play. I think it might be the 12mhz crystal it looked pretty bad when I got it. I cleaned it up a bit.

Image: http://img816.imageshack.us/f/cam0306.jpg/

if your multimeter has a frequency measurement setting (Hz) try measuring the main clock frequency at 7P (pin 10) for 12mhz clock, then at 6R (pin 6) for 6Mhz, then at 6R (pin 8) for 4Mhz. if they are stable at those frequencies during the boot process, then your main clock is ok. also check the E clock out of the processor at 2I (pin 34) which should be at 1Mhz (it is also out of phase with the main clock) E is needed for timing of read/write processes.
 
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....I only checked the 7J chip that andykmv mentioned . I couldn't locate the others on the schematic. I probably missed them, I searched and didn't see them.....http://www.robotron-2084.co.uk/manuals/defender/defender_later_pcb_drawing_set.pdf

Ahhh bugga. apologies, my mistake, i had the joust sheet open and zoomed in for another reason and flipped to it instead of the defender sheet i also had opened and zoomed in. my profues apologies and much embarassment! :eek::eek:

Previous post corrected. :)
 
6R pin8 reads 4.000mHz, chip 2I pin34 reads 1.000mHz. the others read OF witch is over frequency.(meter can only read up to 4mHz)

here is a video of the testing.

http://www.youtube.com/watch?v=6njMXe-BFsk

double checked the theory of operation page 13. Q and E clocks are 1MHz. so E is good. Q should also be 1Mhz. looks like your crystal is good!
 
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