Defender RAM Failure - stuck in rug test

[mecha]

yeah it's like a 50/50 shot you find a cabinet where those are torched lol you always want to replace the caps, headers, and BR1 at minimum with the linears. the voltage regulators I think are kind of an optional thing, if one dies, change it then, unless you have stuff on hand. same thing with the 3055s. there's so many junk ones circulating. that's one advantage of 4164/41256 is you don't have to worry about one of those popping. my Defender (now gone) came with the adjustment pot thing already on its power supply, but I find those silly and unnecessary. 5.00V out of the linear is all you need to run these, especially with 4164 ram if you feed it too much it'll lose its mind.

 

[jetusenet]

OK, next up......

Tried pulling and replacing the PIA and same results so I put the original back in.... same results.

Reset the board several times and I get the rug pattern (RAM Test) and sometimes it does one pass and sometimes I get several passes but no matter, it eventually locks up with the strange LED sequence: 0-1-0-1 (off - on - off - on).

I pulled and replaced all 24 RAM with another manufacturer and same results, so it appears that is attempting the RAM test but gets jammed up.....

Would that indicate a specific issue / IC? (hopefully).

Thanks

Jeff

 

[philmurr]

Have you checked the IRQ, count240 and vertical count buffer? I added something to this topic (#30)

Defender Stuck in Carpet Pattern -> Unit OK Loop

Actually, I already ordered a 5101 chip a few days ago thinking "might as well replace this too..." Glad to hear it was a good idea! Thanks for the help. I'll let you know how it goes.

forums.arcade-museum.com

 

[mecha]

my mind is groggy on such matters, it's been too long, does the rug pattern have any anomalies in it? if so, logic probe pins 7 and 9 (the outputs) to the multiplexers (the one only half is used so it's normal for pin 9 to show low instead of pulse) if the game never actually loads and the rug just scrolls indefinitely then that means the rom board code isn't reaching the ram section. there was a site that displayed all the different conditions you'll have if the rom board is hosed. the rom board PIA being bad will actually get you to the UNIT OK screen but then reset -- along with it you may have no sound (the sound calls at the rom board side go through the PIA), Count240 will not work (it will blue screen and reset back to the beginning of the rug), or the 4 diagnostic LEDs will flash like Christmas lights (which is a cool effect, but symptomatic of a problem!)

the site with the rom board information is down, I'll peruse archive to see if I can dig up the intel on it.

thank goodness I found it: https://web.archive.org/web/20150326034657/http://www.arcadesolution.com/rom.html

I have like 1 working Defender rom board that does the infinite rug and I have to keep smashing the roms back in. bent legs on the chips will be a problem for the single wipe sockets. I don't recall if I replaced the sockets on that or not, I had no broken off pins, and I had to wire brush the rom legs too. real nasty board. one day I need to fix all my broken ones, they're missing PIAs I scalped to fix other games or ribbon cables. LOL

 

[jetusenet]

Have you checked the IRQ, count240 and vertical count buffer? I added something to this topic (#30)

Defender Stuck in Carpet Pattern -> Unit OK Loop

Actually, I already ordered a 5101 chip a few days ago thinking "might as well replace this too..." Glad to hear it was a good idea! Thanks for the help. I'll let you know how it goes.

forums.arcade-museum.com

Thank you very much for that suggestion. I will get back to this rack in a day or so, I need to spend some time with the family now, I was in my basement or the last two days!

 

[jetusenet]

my mind is groggy on such matters, it's been too long, does the rug pattern have any anomalies in it? if so, logic probe pins 7 and 9 (the outputs) to the multiplexers (the one only half is used so it's normal for pin 9 to show low instead of pulse) if the game never actually loads and the rug just scrolls indefinitely then that means the rom board code isn't reaching the ram section. there was a site that displayed all the different conditions you'll have if the rom board is hosed. the rom board PIA being bad will actually get you to the UNIT OK screen but then reset -- along with it you may have no sound (the sound calls at the rom board side go through the PIA), Count240 will not work (it will blue screen and reset back to the beginning of the rug), or the 4 diagnostic LEDs will flash like Christmas lights (which is a cool effect, but symptomatic of a problem!)

the site with the rom board information is down, I'll peruse archive to see if I can dig up the intel on it.

thank goodness I found it: https://web.archive.org/web/20150326034657/http://www.arcadesolution.com/rom.html

I have like 1 working Defender rom board that does the infinite rug and I have to keep smashing the roms back in. bent legs on the chips will be a problem for the single wipe sockets. I don't recall if I replaced the sockets on that or not, I had no broken off pins, and I had to wire brush the rom legs too. real nasty board. one day I need to fix all my broken ones, they're missing PIAs I scalped to fix other games or ribbon cables. LOL

Thank you for searching for that doc, I had actually printed that out some time ago and just came across it while looking through my manuals. Unfortunately it does not help.

My situation is that the rug pattern just freezes, sometimes right away and then sometimes after a few passes.

Just lies dead after that.........

I'll get out the logic probe and give it a go as soon as I have the chance and will of course post the results.

Thanks again for the help and suggestions, it is much appreciated.

 

[mecha]

post a video of what the rug pattern is doing, I might be able to remember something then. perhaps braedel can help better.

 

[dogdayaft]

Defender question?
Is it possible? ,, to get defender game to boot up to a readable CRT with just 3 boards hooked up , CPU , ROM BOARD & INTERMEDIANT BOARD ,
not using any of that "mem prot" or coin door open or closed jazz? thanks..

 

[mecha]

Defender question?
Is it possible? ,, to get defender game to boot up to a readable CRT with just 3 boards hooked up , CPU , ROM BOARD & INTERMEDIANT BOARD ,
not using any of that "mem prot" or coin door open or closed jazz? thanks..

you only really need the MPU and rom board to actually "run" the game. and just leave the middle single red wire plug to the MPU unplugged, it simulates the coin door always being open. lol

 

[dogdayaft]

Thanks..