defender video issues

boilerman

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I have a defender that i had the boards reworked over a year ago and
it worked great. I put it in storage over the winter now it has screen
issues. I hear the start up sound no led lights on the board just a
quick flash on power on. swapped monitors to to make sure no help. I
am a pinball guy and really don't want to put much more money in this
anyone know were to start?

http://imageshack.us/photo/my-images/17/defenderi.jpg/
 
I have not had time to check anything yet but the ps has all 3 leds lit the 4 leds on the circuit board flash once at start up then go out
it doesn't go any further. will a low 5v stop the boot process? or a bad 4116 chip?
 
Mine was doing something somewhat similar and they referred me to a page that shows how to re-crimp the ribbon cable that runs between the cpu board and the rom board. I tried it and it fixed it. It looked slightly different than yours but not by much. Maybe give it a try. Here's the link:

http://www.arcadesolution.com/ribbon.html
 
Check the voltages at the power supply, the MPU header and at the RAM. Very often corrosion will lower the voltages to a point where it will not operate.

Here is a link to what the voltages should be at teh RAM: http://forums.arcade-museum.com/showpost.php?p=1671001&postcount=22

It is in one of jehuie's Defender repair threads, so it may be useful to read the whole thing.

ken
 
I checked the voltages at the ram and got -5.28
+11.14
+4.86
is this enought to stop the boot
 
The -5V is a little high and the +5 is a little low, but they should be within operating ranges.

Whenever you see vertical bars on the screen, it usually indicates a RAM error of some sort.

ken
 
So you think some of the 16 4116 chips are bad?

You might want to start by just reseating them. Or shuffling them to see if the symptoms go away or change. If the legs look grimy you can clean them with Tarn-X but just be careful or you might die in a grizzly fire accident, which isn't funny.
 
Alright removed and reset all 16 4116 in different locations --no change
tested the voltage at the test points on the power supply
+5.02
-5.23
+11.86

what's my next options
 
If I had the board in front of me, the first thing I would do is pull out the logic probe and check the RESET line on the CPU (Pin 37, IIRC). If it is pulsing or low, then it would be time to do some debugging on the clock and watchdog circuits.

ken
 
If I check the RESET line on the CPU (Pin 37, IIRC). should it go high on boot?
If it is pulsing or low, then it would be time to do some debugging on the clock and watchdog circuits.
what parts would you check next?
 
If I check the RESET line on the CPU (Pin 37, IIRC). should it go high on boot?
If it is pulsing or low, then it would be time to do some debugging on the clock and watchdog circuits.
what parts would you check next?

The voltages should be fine to get it to boot. If the RESET line is pulsing, then its time to start checking other things.

I recommend you read through this thread:

http://forums.arcade-museum.com/showthread.php?t=185349
 
thanks..... I'll try get a few hours this weekend and use some of the info in that thread and see if that helps
 
see if that helps

heres some tips i have bookmarked:
http://www.vidpin.com/tech_videorecap.asp

i'd replace all the ribbon cables
love to cross possible trouble spots off the list

i found that a dremel tool with a brass brush is good for cleaning the little spikes that poke into the ribbon cable and make contact with the wire inside the cable

even just cutting off a half an inch of ribbon cable can help if you dont want to buy new. just make sure you line up that just right or more trouble can occur
 
OK had some time this morning to put the logic probe to use here is what i found
pin 37 pules hi to low
Crystal next to 7P top leg low light
bottom leg hi & low stay lit

pin 2 of 7L hi & low stay lit
pin 5 of 7j hi & low stay lit
pin 9 of 7J low light
pin 4 of 6R hi light
pin 8 of 7P low light
pin 12 of 7P hi & low stay lit

I'm pretty new to board repair but my guess is the crystal is bad and needs replacement?
( what are the specs for ordering)

if my theory is wrong what is my next step...?
 
The crystal looks good. Most logic probes aren't fast enough and can't watch the crystal so you need to check a little further down stream to see if the 4MHz clock & 1 MHz clocks are active. The 4 MHz clock can be checked at chip 6R pin 8 and 9. If you are not seeing these pulse, then work backwards to 6R pin 11. This is the clock input. If that is not pulsing, then back up to chip 7P pin 13. If pulsing then check 7P pin 11. If pulsing then check 7P pin 9. Walking this set of components will verify that the 4MHz clock is active.

Chip 7L pin 5 is the E clock to the CPU.
Chip 7J pin 5 is the Q clock to the CPU.

ken
 
ok here the results of the lastest checks 6R 8,9, 11 hi/lo both lit
7P 13,11 hi/lo both lit
7l and 7j #5 pins both hi/lo both lit

Now what is there anything i can change out to start getting better results?
 
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