Help with Defender plz

wickedbass

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She was working fine the other day now today i get this

initial test indicate ram failure...at least im pretty sure thats what it says. the letter are kind of messed up..

any ideas? so far ive reseated all the roms and still get same message.:(

DSC03413.jpg
 
initial test indicate ram failure...at least im pretty sure thats what it says. the letter are kind of messed up..

Yeah... bad RAM...

Unfortunately defender's RAM test sucks and won't tell you which RAM is bad...

I always meant to port the Stargate RAM check back to Defender as a test ROM, but never found time...
 
Would i be able to tell the bad ram by touch..will it get hot?..

dave i dont see it labled..where is #24?

Thanks
 
I think he meant check all 24 ram chips. There should be 8 per bank.

Stargate actually tells you which ram is bad. Apparently Defender does not.

I would just go through and reseat them all and see what happens.

Options would involve 1) getting a few new ram chips and replacing a few at a time to see if that corrects the problem or 2) getting all new ram or 3) upgrading the ram to a different kind that is supposedly more reliable. I say supposedly because I've still gotten ram errors after doing the upgrade.
 
I think he meant check all 24 ram chips. There should be 8 per bank.

Stargate actually tells you which ram is bad. Apparently Defender does not.

I would just go through and reseat them all and see what happens.

Options would involve 1) getting a few new ram chips and replacing a few at a time to see if that corrects the problem or 2) getting all new ram or 3) upgrading the ram to a different kind that is supposedly more reliable. I say supposedly because I've still gotten ram errors after doing the upgrade.

Great thanks for the suggestions. i like option #1.
 
Check all your voltages coming out of the power supply.
You should upgrade the ram to 4164 and never look back.
4116 rams run really hot normally so if you have one thats ice cold it could indicate a problem.
 
Whenever there is an initial indication of a RAM failure in a Williams board, always check the power supply first. It is amazing how many RAM "failures" are fixed by making sure the power is working correctly.

Measure the voltage at the 4 corners of one of the RAM chips.

The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground

The pins are numbered starting in the upper left corner (notch being up), going counter clockwise.

If any of them are low or are fluctuating more than 0.1 V you need to replace your power supply.

ken
 
Whenever there is an initial indication of a RAM failure in a Williams board, always check the power supply first. It is amazing how many RAM "failures" are fixed by making sure the power is working correctly.

Measure the voltage at the 4 corners of one of the RAM chips.

The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground

The pins are numbered starting in the upper left corner (notch being up), going counter clockwise.

If any of them are low or are fluctuating more than 0.1 V you need to replace your power supply.

ken

Thanks for the tip and instructions Ken:)
 
3) upgrading the ram to a different kind that is supposedly more reliable. I say supposedly because I've still gotten ram errors after doing the upgrade.

I won't sell a board w/o doing the 4164 upgrades... got burned a couple times with boards that worked fine on the bench and in my game, but not so much with someone else's PS/harness.

If you're still getting RAM errors after the upgrade, replace the sockets.
 
...and actually, though it's hard to really tell from the terrible picture (lose the flash, turn off the lights), I don't see any stray pixels that are often indicative of a bad RAM -- almost looks like address decode, so you should check the 2 decoder ROMs (and sockets) and/or the 74153s.
 
I checked out Brian's board last night. It's not the RAM or the decoder ROMs (unless it's a socket issue, but I don't think so). Unfortunately, I didn't have a test harness handy to put the board on the bench and probe it.... I told him it might be one of the six 74165's, but Mark is probably right, so you should check the 74153's first (they're at 3G, 3I, 4F, and 4H). I suppose it could be one of the 74374's (1M and 3M) too, no?
 
I checked out Brian's board last night. It's not the RAM or the decoder ROMs (unless it's a socket issue, but I don't think so). Unfortunately, I didn't have a test harness handy to put the board on the bench and probe it.... I told him it might be one of the six 74165's, but Mark is probably right, so you should check the 74153's first (they're at 3G, 3I, 4F, and 4H). I suppose it could be one of the 74374's (1M and 3M) too, no?

74165's are only video out... completely unrelated to the RAM error, but could cause the pixel doubling...
 
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