Defender RAM Failure - stuck in rug test

Superully

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sometimes this hobby SUCKS BIG TIME!

just yesterday i had fixed my defender sound issue, but when i turned on the game today, it came up with the screen "initial tests indicate ram failure". well, in fact the screen didn't really come up at all. turning on the game it started with the rug test (that's what those colored screens are called, right) which took longer than normal, then i could the the ram failure screen for about 2 seconds and the rug test started again.

so basically i don't get into the settings / test screens at all, but the game is stuck in rug test mode! :(

from the four leds on one of the pcbs, leds 1 and 4 are ON, 2 and 3 are OFF!

what am i supposed to do next? reseat all the rams (how many are there?)? i've read somewhere to replace the old rams with new 4164 rams? is this simply a "run and hide" operation or do i have to change something else as well then?

any help / input is totally appreciated, i wanna play that game again badly!!! :)
 
Test at the 15 pin connector coming off of the power supply first.
1 orange wire -5
2 key
3 reg +12vdc
4 unreg -12vdc
5 unreg +12vdc
6 unreg +12vdc
7 gnd
8 gnd
9 gnd
10 gnd
11 NC
12 +5vdc
13 +5vdc
14 +5vdc
15 +5vdc

Second test at the RAM chips on the corners. I don't recall which corner is which.
one is +5vdc
one is -5vdc
one is +12vdc
one is gnd
 
sometimes this hobby SUCKS BIG TIME!

just yesterday i had fixed my defender sound issue, but when i turned on the game today, it came up with the screen "initial tests indicate ram failure". well, in fact the screen didn't really come up at all. turning on the game it started with the rug test (that's what those colored screens are called, right) which took longer than normal, then i could the the ram failure screen for about 2 seconds and the rug test started again.

so basically i don't get into the settings / test screens at all, but the game is stuck in rug test mode! :(

from the four leds on one of the pcbs, leds 1 and 4 are ON, 2 and 3 are OFF!

what am i supposed to do next? reseat all the rams (how many are there?)? i've read somewhere to replace the old rams with new 4164 rams? is this simply a "run and hide" operation or do i have to change something else as well then?

any help / input is totally appreciated, i wanna play that game again badly!!! :)
hi, still aorund, just wondering im getting the power up rug screens too, and can sometimes vaguely see the ram failure text.
what did you do to resolve this rug screen error?
thanks
m
 
Hi,
I have what seems to be the same issue, RAM after RAM failure using the newer 4164's.
Replaced a few and then got game, burned it in and about 2 hours later, getting the RAM FAILURE display, the number of the failed RAM slightly visible, "particles" of the alphanumeric characters assembling and disassembling (reminds me of the 'ol days :cool:) and sometimes if I leave it on, get the full readout of the RAM location.......
Gonna pull all the 4164's of a certain manufacturer and replace with another manufacturer and see if that helps....
Will post the results once I do.
Jeff
 
.........what's funny is that I was trying to save time and not replace the RAM sockets as the pulled RAM looked decent and so did the sockets..... So much for that idea......

Pulling and replacing tomorrow......
 
if you have the time to do it, more power to you. 4164 ram as I have stated for years now is significantly more voltage sensitive than the 4116s they replace. if you're using a switching power supply you need to verify you have 4.90-5.00V to the chips (you won't hurt these rams, but I suggest voltage testing somewhere else as a standard practice...) if you're sitting below 4.85V you will get erratic errors all over the place and the artifacting. if could be a sign of a larger issue, I had boards that seemingly worked perfectly that just vomited on 4164s... that's when I disconnected the +5V from its old spot running to 4164 A7 and attached ground in its place. you're supposed to really ground unused gates, as you'll see on the half used multiplexer and I think one of the 74367 address buffers the unused pins are tied to ground.

I'll reiterate again, as the prices are comparable between the two lines, 41256 rams in my experience don't exhibit the weaknesses of 4164s. with those, however, you have to remove the -5V supply to the ram section as those chips have an A8 in that spot and it will kill the rams.

I had enough negative experiences with 4164 ram that I just stick with the 4116s. those aren't necessarily bad by their design, they're just 40 years old now and you're prone to have some bad ones. buy 4164 ram from Arcadeshop and you'll have a lot of duds out of the box. ^_^
 
Thanks for the response, I appreciate the insight and also that there is another alternative to the 4164's.

To follow up, I have already grounded A7 on the 4164's, that was a suggestion I picked up on the Forum. At this point, I have replaced all the sockets and that did clear up my "dissolving" text.... Put back the 4164's I had started with and had one RAM failure 18. Replaced that and got game!

Well, temporarily.......

Played a few 2 player games without issue, left it powered up while doing chores and when I returned about 30 min. later, came back to a white screen.........

Rebooted and came up with the expected and happy to see, "Initial tests indicate unit OK" and just hangs.......

Rebooted several more times and it consistently comes up with the, "Initial tests indicate unit OK" and continues to just hang, Advance etc. have no effect on the game, just locked up...... and now it looks like I lost vertical sync as well, the display of "Initial tests indicate unit OK" just scrolling upward for eternity....

It appears something that tests (and plays) good goes bad when it get hot.....

I'll swap ROM #2 and ROM #3 with known good and see it that has any effect, then onto the schems to see why I lost sync.

Thank you everyone again for the suggestions, every bit helps!

Jeff
 
OK, spent another few hours on this beast and found bad sockets on the ROM PCB.... Pulled them and found corrosion underneath the sockets so since I was at it, pulled all 12 X 24 pos sockets and found a couple bad traces. Replaced all the sockets, repaired the traces (jumped) and retested all the EPROMs and fired it up.

Now I get the start-up sound and then scrolling rug pattern..........

Replaced 3A (7486) and 3B (7411) and gave it another go.....

Now I still get the start up sound and something new, a nice steady frozen rug pattern (nice - no more rolling) with LED #1 and #3 lit on the ROM PCB. I cannot find that error code anywhere..........

Swapped the NVRAM with a known good - no help.
Swapped Decoder ROMs #2 and #3 with known good - no help.

To recap, when power is applied, I receive the start-up sound, a static rug pattern and LED #1 and #3 lit.

Buttons do nothing and only hitting the reset changes anything.....

What's funny is that this darn set was working fine, then just fell apart!

If anyone have any ideas where to look................. would bad color RAMs cause this to happen????

Thanks again

Jeff
 
color rams won't have any influence over anything else unless they were like monumentally shorted and flooding the data bus. the rom board lights are more indicative of something wrong in the rom board I think. do you have another working one to swap in?

also was this a battery leak board? I have seen them where the traces die without leakage. strange things.
 
This was not damaged by battery leakage and that it why I spent so much time on it, as it is for my collection, I do not mind going the extra mile.

Another item to mention is that my test rig needs the voltage control full CW which is unusual. There is no specific IC getting hot so I do not know how to explain that. I measured voltage at the RAM and it is 5.01vdc so that is not the issue.

Unfortunately I do not have a known good ROM PCB so at this time so that is not an option.

I tried looking up that strange LED sequence but I cannot find that anywhere.

Whats funny (no so) is this board gets repaired, works for a bit, breaks down, gets repaired and once again works for a bit..... a real ball buster if I do say so myself....

Thanks for the help...

Jeff
 
BTW, I like your idea doubling up on the A/C lines, I always check the schems (and traces) to utilize the "undocumented" and available pins on the power headers.

Costs a bunch more when making my own harnesses but I have never had issues with burning pins / contacts or voltage drop when doing so...
 
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