Just picked this up on Friday!

KevinSin

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Donor 3 years: 2012, 2014, 2016
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Picked this up for $200

It doesn't work but it is complete and the cab is in excellent condition!

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More Here: http://s16.photobucket.com/albums/b19/kmk68sin/Defender/
 
I saw 2 of those down in the los angles area..The cabs were show pieces but they had issues. I wonder if one of them made it up there? most likely not...

Great buy best of luck in repairing it..
 
defender

this is one of my favorites. spent alot of quarters learning the controls.
but once you get the hang of it, the game is pretty easy. congrats!
 
Thanks everyone! I look forward to working on it! I think I'll start with the basic troubleshooting tonight and go from there. :) I WILL get this working...it would be a slap in the arcade gods faces not to LOL. I'll keep you updated!
 
Actually I did drive down to San Jose to pick it up. The guy I bought it from was really nice and bummed to sell it. I told him this Defender is in good hands and that I'm on KLOV if he needs me :)
 
Ok, I started troubleshooting the Defender. I only spent an hour on it but I was able to verify that power is not an issue. I'm getting proper voltages all over the boards which means I'm down to the boards themselves next. I reseated all the ROM chips so now I will start checking the RAM chips out.
 
Ok, I started troubleshooting the Defender. I only spent an hour on it but I was able to verify that power is not an issue. I'm getting proper voltages all over the boards which means I'm down to the boards themselves next. I reseated all the ROM chips so now I will start checking the RAM chips out.
What exactly is it doing? After reset, you should see two passes of rug test, a quick blue screen, self-test results. If you get a bunch of vertical stripes, that indicates that the CPU is not able to execute from the first ROM correctly.

LeChuck
 
Yeah, what's it doing. It still might not be the boards. I've had several of them that had issues with the ribbon cables. Doing a re-crimp on those might fix it too, depending.
 
Well, when you turn it on the screen comes up and it shows a grid (kind of like a huge maze being viewed from space) other times when I turn it off and on it the screen looks like one of those magic eye posters they had in the 90's. I swear if I stare at the screen and see the image I might be able to play the game LOL. I'm rather new to troubleshooting the boards so bear with me. I am printing up the manuals now so I can test the chips with a logic probe to make sure they are working properly.

How would I recrimp the ribbon cables? I reseated those and they seem to be in good shape.
 
Well, when you turn it on the screen comes up and it shows a grid (kind of like a huge maze being viewed from space) other times when I turn it off and on it the screen looks like one of those magic eye posters they had in the 90's. I swear if I stare at the screen and see the image I might be able to play the game LOL. I'm rather new to troubleshooting the boards so bear with me. I am printing up the manuals now so I can test the chips with a logic probe to make sure they are working properly.

How would I recrimp the ribbon cables? I reseated those and they seem to be in good shape.
Here is a link about replacing/repairing the ribbon cable:
http://www.arcadesolution.com/ribbon.html

If you suspect your ribbon cable is flaky, you can try reconnecting or physically wiggling it to see if it affects your results (or preferably, check the continuity on each wire of the cable with a multimeter).

The "maze" sounds similar to the jail bars you get if the CPU has failed to execute from the first ROM - can you post a photo? Do you get the same maze if you power-up with the ROM board completely disconnected? That would be indicative of something failing at the CPU (e.g. bad power, bad clock, reset not deasserting), or the CPU being unable to access the first ROM (e.g. bad ribbon cable, bad ROM contents or socket). Normally this results in vertical "jail bars" though, so it's possible you have another issue going on, such as bad RAM decoding.

If the CPU is working, it should start executing the self-test from ROM 3. This will perform two passes of RAM tests (each one producing the "magic eye" or "rug" pattern) and checksum the ROMs. This self-test is running entirely from ROM 3, so you shouldn't need anything but the CPU and ROM 3 access working to get this far.

After this, it uses ROMs 7, 8, 10, 11, and also a small portion of RAM, to clear the screen and display the results. Do you get this far? If not, do you get a quick blue screen before it resets?

Also just to clarify - what tools do you have available? Do you have any spare boards to swap in?

LeChuck
 
OK, made a bit more progress tonight. I tested the voltages on the 4116 RAM chips on the cpu board and they all register correct voltages (-5v pin1, 12v pin8, 5v pin 9), tested continuity on the ribbon cable (all 40 pins were fine), checked the socket on the ROM 1 chip as well as reseated all the ROM chips. I do get the same grid image when I unplug the ribbon cable.Then when I plug the cable back in and turn it on I get two quick screens of a rug pattern and then a dim blue screen. (possibly ROM 3 is bad?) Tested the sound board and I know that works fine because it scared the shit out of me when I hit the test button since the volume was up all the way. i put new batteries on the cpu board. I have no other defender boards to swap out for testing. do you think it could be the 6809 CPU chip? Or possibly one of the ROM chips? When I first turn it on, I get image below, sometimes it's just a blue screen.

Here are some pictures of the screen:

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The already-mentioned arcadesolution.com website has some troubleshooting tips for Defenders (in the "Self Help" section). Check out the Rom board troubleshooting subsection...it sounds like you might indeed have a bad ROM.

Andre is a great resource, too, he can fix the boards for you if you are unable to do so yourself, and his rates are very reasonable. Or he can sell you an individual board working if that's all you need.

I recommend getting a switcher power supply from Bob Roberts even if your power seems OK now. They are just more reliable in the long run, not that expensive, and ultimately help protect your boards from failures down the road. I have switchers in all of my Williams games, and I rarely have any problems with them anymore (knock on wood!).

Also replace that CPU to ROM board ribbon cable for sure! Again, it's another high failure point regardless of whether it is the source of your actual problem right now.

If it turns out you need to burn new ROMs, you're not too far at all from me and I have a burner that should do the trick (if you supply the ROM chips). And although I don't have an actual Defender in my collection (I play the game via JROK's multikit in my Stargate :D ), I do have access to my neighbor's Defender if we want to test individual boards in his game to see if we can narrow the problem down to a particular board. He literally lives just down the street from me...I helped him to fix his Defender a few months back when I first moved to the area and he saw my garage/arcade open and approached me saying he had some classics of his own that were not working and could I take a look.

I fixed both his Defender and his Dig Dug (they were apparently down for many years!), and now we're good friends, too, and our respective kids like to play together, too :)

Anyway, LMK if you want to hook up via PM.

And congrats on a very cool pickup!

Jon
 
Funny thing is I printed up the ROM troubleshooting section from the arcadesolution.com site this morning :). I will definitely test this out tonight to see if I can pinpoint the problem. I will also replace the ribbon cable even though it checks out just so it will be one less thing to worry about moving forward.

I might take you up on your offer if it is a bad ROM chip. It gives me an excuse to meet another local collector in my area. ;) Either way we should meet up, grab a beer and play a few arcades since we are local. I cannot stress enough how excited I am to meet more people into this hobby in my area! I'll PM you.

This is my first board repair to this extent. Usually I just swap out boards, not repair them, but that is going to change now. I want to start repairing my own boards.

I'll post the results later tonight.
 
From your description, it sounds like you have two issues:
  • Sometimes the CPU is failing to execute successfully from ROM 3
  • Sometimes the CPU successfully executes self-test, but resets just before displaying the results (two passes of rug tests, quick blue screen, repeat)
How frequently does it exhibit each of these failures? Is there any pattern to reproducing one or the other?

I would personally try to figure out the first issue so you can reliably debug the second. I would initially presume the CPU is working (although it would help if you could confirm the CPU clock, reset, and power are all normal when the first failure occurs). Most likely it is failing to fetch code from ROM 3, so you end up with jail bars or a blue screen. The first thing the power-up code does is initialize the background palette to blue and clear the screen .. so if you die there, it didn't make it very far.

Some thoughts:
  • Does the behavior change at all if you physically wiggle the ribbon cable connection while it's powered on? You might try this at various parts of the cable, and on the connector ends. Just trying to rule out an intermittent failure on the cable. I personally prefer to prove something has failed before replacing it; bulletproofing comes after root cause. But if you want to swap parts, make sure to do it individually (so you know which one made the difference).
  • Can you confirm the continuity of the ROM 3 socket and legs? Again, it sounds like you're looking for something that is intermittently breaking ROM 3 access.
  • Do you see expected pin states on ROM 3 when the failure occurs? It's not 100% reliable, but it may give a clue to make sure ROM 3 is seeing good power, chip select, and activity on the address/data lines (e.g. on the off chance that you find a stuck line, or chip select not asserting).
Since you can sometimes make it all the way to the end of self-test, it sounds like your ROM 3 contents are good. I would focus on what is changing that makes/breaks access to it.

I'm sure with enough probing you can figure out what's going on. If you get stuck though, I wouldn't mind taking a look if you felt like shipping it out (I would start with just the ROM board and go from there).

LeChuck
 
Funny thing is I printed up the ROM troubleshooting section from the arcadesolution.com site this morning :). I will definitely test this out tonight to see if I can pinpoint the problem. I will also replace the ribbon cable even though it checks out just so it will be one less thing to worry about moving forward.

I might take you up on your offer if it is a bad ROM chip. It gives me an excuse to meet another local collector in my area. ;) Either way we should meet up, grab a beer and play a few arcades since we are local. I cannot stress enough how excited I am to meet more people into this hobby in my area! I'll PM you.

This is my first board repair to this extent. Usually I just swap out boards, not repair them, but that is going to change now. I want to start repairing my own boards.

I'll post the results later tonight.

No problem, I work in the city a couple of days a week.. If you need me to swing by, just let me know and I'll bring a Defender MPU and a ROM board - maybe we can narrow it down to one of the two and go from there. If you have a 6809 CPU from another game that you want to try and swap in, go for it - it won't hurt to try (since you verified stable voltages from the PS.) If you need a ribbon cable, I have plenty on hand to do a cable swap - in fact, I always replace them on the Williams ROM boards, fairly easy to do.

-Muel
 
Ok, last night I replaced the ribbon cable, pulled all the rom chips and cleaned the legs, pulled all the RAM chips and cleaned the legs, pulled the CPU and cleaned the legs and now I get all kinds of random things on the screen. After doing the ROM tests by removing all the roms except Rom 3,7,8,10,11 and slowly adding Roms nothing really changed.

At this point I think what I may do is swap out the power supply with a switching power supply just in case the RAM is not liking the current voltage levels. What I want to do is adjust the voltage levels to see how this affects the outcome. (see if it changes). I'm also convinced that ROM 3 is bad since I did not get any error codes in the ROM tests. If that still doesn't fix it, then I'm left with replacing the CPU chip.

Any other recommendations?
 
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