Defender Toasted MPU

[RetroHacker]

The coindoor's not an original Defender brushed metal, although I wish.

Well... it is factory original - just not the version you want . They used the silver door only on the early Defenders. Later ones had that black door you have. You can't swap the doors around either, IIRC, since the mounting holes are different. I *think* the silver door is actually larger, so to fit one on a late version cabinet, I think you have to do some cutting. But don't quote me on that - I may have it backwards.

-Ian

 

[Jimjaycee]

The first Defenders incorporated the coin door that Williams used on their pinball machines.
It was probably a lot cheaper for them to go with the standard arcade video coin door so they made the switch.

 

[AMG]

The only thing I can see as a difference is with the plugging and pulling, you could theoretically crack that pcb mounted off the side of the as version.

Since the BR switcher has that pigtail harness included, you can mount the PS in an out of the way location without having to do anything to the original harness. And I didn't like having the pcb on the AS supply being mechanically stressed like that either.

 

[AMG]

Yea, like you, I'd much rather run the Robotron version but didn't see anything on epay.
Although, I'm not sure with that, how badly I'd have to hack up an original harness? I really don't want to do that. I'd like to keep it as original as possible, yet as 'safe' as possible.

You don't need to change the harness at all. The 12-pin connector from the Defender transformer plugs onto the 15 pin input header of the Robotron/Joust PS - just make sure it lines up correctly (I removed the 3 extra pins). Then you add some jumpers (the cocktail mod to make your coin door lights work) and the PS is good to go. It doesn't mount exactly the same way as the Defender board does, but I was able to mount it by relocating one of the original mounting brackets. Thanks to Ken for explaining all that a while back.

I may just go ahead and order BR's version, as I'm going to pick up the Lithium battery kit and try my best with the board I've got unless someone has a working MPU for sale. I can't see any harm in trying to run this board.

No harm in trying that board, but if it took a big voltage hit it may not be reliable down the road. I have a couple of working Defender MPU boards I'd be willing to part with, PM if interested.

 

[YellowDog]

I thought the 5114 disabled writes at a voltage above where the 6809 goes screwy, it sucks that they're all susceptible. How often does it hit non-Defenders? I've never run into a switcher issue on Stargate and up machines.

It doesn't hit non-Defenders as much. The Defender CMOS protect circuit was lifted from the pinball MPU boards and 6800s are a little slower on the trigger to spray memory. They tweaked the circuit slightly in the Stargate and up to run better with the 6809s, but it does still happen.

ken

 

[Zinfer]

Hah - well how about that. I had no idea. Yea everything on this cabinet from MPU to sound card is pointing to it being a later version cabinet. I thought all versions of defender originally had the brushed metal coin door. Cool. I learned something today.
Well I placed the order for the PS. Just gotta pay for it and wait at this point. I ordered a full compliment of ram, I've used up all my 4 16pin sockets. Ordering more of those. I tested out all the Eproms on the rom board. Verified the sound boards' eprom. Hopefully will have some positive news in the coming weeks.

Well... it is factory original - just not the version you want . They used the silver door only on the early Defenders. Later ones had that black door you have. You can't swap the doors around either, IIRC, since the mounting holes are different. I *think* the silver door is actually larger, so to fit one on a late version cabinet, I think you have to do some cutting. But don't quote me on that - I may have it backwards.

-Ian

 

[Zinfer]

Ok, power supply replacement/switcher arrived along with the Ram. I have it all hooked up. I'm missing the 2nd light to the left on the Rom board. It's out.
Ran a heat check on Ram and replaced those that were burning hot. Since there's no display on an onboard LED such as is on Stargate, Joust and the like, it's hard to tell what's going on.
I have neck glow, but I don't have any video output. Just a blank glowing/flickering screen.
I mean even if I pull a ram, shouldn't I get some kind of report that I've got bad ram at x location?

 

[Zinfer]

Well I went ahead and used up all the new 4116 Ram, replaced every last RAM with brand new. No change though.
LED 2 always off 1,3 and 4 always on. Is that sounding like a Cmos Ram issue?

 

[Rampart35]

Repair guide

I noticed your 'adventure'. I have worked on some Defender boards, but I've never seen a RAM fried like that.... Wow, I know 4116 RAM runs hot(use +5, -5, & +12V), but wow!

Not sure if you have this, but I found this guide very useful: http://arcarc.xmission.com/PDF_Arcade_Williams/Defender_Recap_CPU_Part_1.pdf

Good Luck!

 

[Zinfer]

Yea- well...how it was supposed to work was - I rework the sockets, pull all the ram, replace and whallah! Just kind of a lucky fix. That's not appearing to pan out right now. Apparently there's something else wrong. Or maybe many something else's.
Man, you know. It drew me back in repairing Tron, Asteroids, Stargate, Berzerk - then for the last 3 mos has been nothing but badness and negative reactions to fixes that were supposed to work. I'm just on a bad streak - or need to get back out for a while. Cause every fix I run on every game - fails.

 

[Zinfer]

That is a very interesting document. Just for the heck of it I hit step one. Checked pin 37, strobing high and low, then I hit reset and it went high for 1 second. But according to the document, it's supposed to go low. hrm...

I noticed your 'adventure'. I have worked on some Defender boards, but I've never seen a RAM fried like that.... Wow, I know 4116 RAM runs hot(use +5, -5, & +12V), but wow!

Not sure if you have this, but I found this guide very useful: http://arcarc.xmission.com/PDF_Arcade_Williams/Defender_Recap_CPU_Part_1.pdf

Good Luck!

 

[AMG]

Checked pin 37, strobing high and low, then I hit reset and it went high for 1 second. But according to the document, it's supposed to go low. hrm...

Pin 37 on the cpu is ~reset - read as "not reset" or "reset, active low". Under normal circumstances that pin should be high. If that pin is pulsing the cpu is continually resetting, and the game won't do anything. Hitting the reset button should activate the reset - ie. cause ~reset to go low, not high. Sounds like you found the next part of the board that needs work. The flowchart may help some more, or grab the theory of operation manual and check out the reset and maybe the watchdog circuits.

 

[Zinfer]

meh - been down this road before. You start going down the rabbit hole and then bleh. So, I think I'd rather just swap this with cash for a working boardset.
Sorry, been down this road too many times. It was worth a shot for a lucky ram rework/replace. It didn't work - count it as a loss.
I'll just end up getting tired of it and turning to another project.
Ive installed 24 brand new Rams and a lithium kit. Any Defender repair guys want to swap for cash?

 

[Zinfer]

Bringing this part of the story to a conclusion, my hats off to AMC Solutions. Outstanding work getting this slightly crispy classic back to life. Thanks Andre