Defender questions

mahnomen

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I recently bought a Defender stand up game. The thing is totally original. When you turn it on, you can hear the music, and the screen is garbled with different colors. You cant start a game, or anything. However you can go into the test modes, and it comes up Ram Bad, Rom Bad. Where do I start with this, and is it fixable???
 
This is the cheapest place to get RAM chips -- http://www.arcadechips.com/product_info.php?cPath=27_21&products_id=44

I'd fish ebay for a ROM board or else ask Yellowdog if he has one to sell.

Otherwise you can try to fix it yourself with Defender pdf manuals, a Logic probe, a Logic Analyzer, soldering / desoldering equipment, and a Digital Multimeter. - That's all the equipment I got!

I think Yellowdog does Defender repair and you can just send him all of your PCBs and he'll fix them.

I bought a lot of Defender IC chips from this place, has the cheapest price for them and largest selection. http://unicornelectronics.com/prod.htm
 
As Mod said. WIth a Williams game always check the power. Easiest place to test (if you are careful) is the RAM chips on the CPU board.

Measure the voltage at the 4 corners of one of the RAM chips.
The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground
The pins are numbered starting in the upper left corner, going counter clockwise.
If any of them are low or are fluctuating more than 0.1 V you need to check your power supply.

If the power is good, then I would check the connectors. unplug and reseat the connectors from the power to each board and between the ROM board and the CPU and the I/O board and the CPU board.

If that doesn't fix it, we can talk about repair/replace parts.

Pictures of your boards would help also. There were 2 versions of Defender boards and not all the parts are interchangeable.

ken
 
There were 2 versions of Defender boards and not all the parts are interchangeable.

Hey Ken, could you expand on this a bit? I know cocktail machines need the new CPU (with decoder chips 2 and 3), the new style I/O board and red ROMs, but are there other incompatibilities in the Defender hardware?
 
The old sound boards will work with all of the Williams CPU's but the early Defender CPU's will apparently only work with the early ROM boards. At least I have never gotten them to work together. I have never had a working early ROM board to test with a later CPU board so I am not sure if that combination works. I have seen reports that the early I/O boards will only work with the early Defender boards as well, but there have been some reports that they will work with the later CPU boards, but not Stargate boards.

As you can see there is a lot of maybe this, maybe that information out there. I have never had complete sets of both working at the same time to be able to do a definitive mix and match of components to see which parts work in what combination. So for now, it seems safest to say early Defender parts go together and later Defender parts go together except the sound cards which seem to be interchangeable.

ken
 
I can clear up a little of it. My Defender came with an old style ROM board and a new CPU, and it worked fine (with both green and red rom sets). My only Defender I/O board is the old style, and it works with the new CPUs. I've never had an old CPU or sound board, or a new I/O board, so I can't say about the other combinations. Do you know if Williams changed all the boards at the same time, or did they phase them in one new board type at a time?
 
Both early and later I/O and sound boards will work with both Defender CPUs apparently. I have not had a set of early boards at the same time I have a later set where both sets are working, so I have to go by what other people have said.

The I/O board changes are relatively minor, so I can see that both I/O board types would work with all the CPU's. The same with the sound board. The interface stayed the same so they should work with all CPU's. The major difference was adding support via the jumpers for the larger EPROMs.

The ROM boards are where I have heard the most issues occur. The last time I had an early CPU board, I didn;t havea working ROM board. I now have working later ROM boards, but I am not sure the early CPU that I have works.

As to how the boards were phased in, that I couldn't tell you. That was before I worked at Williams. And even then, that would have been a production decision amd might not have trickled back to the programmers. Maybe some of the old time operators can answer that one.

ken
 
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