TECH:Two Lunar Lander issues no y or z out & a "resetting" issue.

Hello,

I thought it was time for me to actually join this list since I have 3 vector games that always seem to need one thing or another. I spent a several hours over the weekend going through the list archives and I was very impressed with the knowledge base of the people here and the intelligent thought provoking discussions with minimal flaming. I have grown slightly weary of RGVAC and all the FS/FT, flame wars and general BS etc. I look forward to participating where appropriate with this group.

I've been collecting for about 6 years so I've been around the block with some minor board and monitor issues (edge connectors reseating sockets, replacing sockets, burning eproms, cap kits etc.), but as yet I haven't done anything along the lines of logic troubleshooting. That brings me to this point... requesting some help.

I rescued this Lunar Lander from a partially burned out barn. It's actually in great shape especially considering what it's been through. If it were junk I wouldn't even be bothering with it, but there are relatively few LL's left...

What I've done so far: the symptoms have remained consistent throughout all these changes so I haven't mucked anything up. I replaced the edge connector and pins. There were 2 eproms missing so I replaced those (the self test eprom was one of them). Most of the eprom IC sockets had some corrosion on them so I replace all the sockets. I also replaced big blue because of a buzzing issue. I capped the AR board. I also installed ic sockets for the 2- 2111's (the 9111's had been socketed previously with 2111-1s. I simply replaced the corroded socket) and I socketed the 4- 2114's. A potential issue may be that the 2111a-4's @ e/f-2 were replaced with 2111-1 running at 500ns instead of the <450ns typical. Finding the proper 2111a4 has been elusive. All board voltages are where they should be.

I have 2 issues and I'm not sure which one to tackle first.

Issue1:

Basically the story is that my LL passes the self test, but will not play in game mode. In self test all beeps indicate all is well and I can hear the 3 thrust sounds and the crash sound just like it's supposed to. However when I flip the switch to game mode nothing really happens. It would appear that the game is resetting. The X out will show up on a scope for about ½ a second then flat line for ½ a second, then show up again... this consistently repeats until I shut it down. In self test X out on the scope shows up just fine no resets. I have tried grounding the WD and the coin counter clicks 3 times then nothing then it clicks 3 times again. I haven't been able to find an explanation for this yet. I did my best to use my logic probe to check a few things out to see if there is a problem with the watchdog circuit, and I found that pin 40 on the 6502a is being held HI so the CPU doesn't appear to be resetting. Can anyone think of some other things to check?

Issue 2:

There is no Y or Z out voltage X shows up just fine. Sometimes for the first 5 seconds or so there will be some activity on the X axis but it eventually flat lines Can anyone think of what may cause this? I have checked the entire board for broken traces and the both of the y trim pots checked out fine. I have unhooked the monitor until this output issue can be resolved for obvious reasons.

Any idea which of these two issues I should tackle first, or does it not really matter?

LMK if there is any more information required, it would be nice to resurrect this game... More importantly I would like to fix this game myself (with help from the group) for the satisfaction of reviving it.

Any ideas or assistance is ***greatly*** appreciated.

Thanks for your time.

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Received on Thu Aug 22 13:28:54 2002