Defender issues

wraywray

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Picked up a defender today. Was told monitor was shot but it isn't. Was told the boards worked but they dont. Got a good deal on it so I took it. Here are my issues. Sound repeats over and over and will not go into test mode. Screen is blank. I have a switching ps on it so voltage is good. As you can seen in the pics the ribbon was broken so I tried to put it back on. All 4 led lights are on. I have been reading that the ribbon can cause some issues that might be related to mine. What do you think? And if this has came up before (sorry I looked but must have missed it) where do I start? I know the ribbon but assuming it isn't the issue and power isnt where do I need to look to?
 

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if it was the ribbon you would be seeing a rug pattern. what I see from your picture is a monitor with the Screen brightness cranked up so high all you see is retrace lines. start by turning the flyback down until the lines disappear.

the switcher additionally won't mean much if the filter capacitors on the MPU are trash. not you, but I don't know why people don't grasp this, you can lose up to 3/4 of a volt across those caps.

in the PSU guide in my signature is a picture of an IC, it shows how to measure voltage on it. don't do this at the 24 ram chips because undoubtedly that's the only time people's hands get unsteady and they wind up destroying numerous ram components. choose another chip close to the headers, that's how you will determine where your +5 is at. your game appears dead, so I'm going to venture a guess that the voltage is morbidly low.

also verify that you have 3 capacitors by the power plug on the MPU, 100 uF/25V. if they're somehow missing like they were on one of my boards then you will have no voltage going to the chips. :)

the power plug has a variety of different colored wires, this is where you can obtain your reference voltage for the +5 at the grey wires. you can also sample the grey-yellow and grey-white (regulated and unregulated +12) and grey-green (-5) too. the ground is the black wires.

the Williams guide in my signature is usually somewhat helpful, but your game looks completely dead. please take pictures of the actual power supply showing how the wires are connected to the lugs, and take pictures in sections of the MPU board, so I can see if you're missing any chips.

also make sure the monitor has a video signal coming into it, they'll be purple wires, and they connect to the middle big plug on the MPU. and last, from a diagnostic standpoint, the rom board will show all 4 LEDs because the MPU is probably not working at all.
 
thanks! i will test voltages and take some pics. i will try and do this in the next day or so as i am swamped with work. if i didnt need the money for my damn arcade fix...

if it was the ribbon you would be seeing a rug pattern. what I see from your picture is a monitor with the Screen brightness cranked up so high all you see is retrace lines. start by turning the flyback down until the lines disappear.

the switcher additionally won't mean much if the filter capacitors on the MPU are trash. not you, but I don't know why people don't grasp this, you can lose up to 3/4 of a volt across those caps.

in the PSU guide in my signature is a picture of an IC, it shows how to measure voltage on it. don't do this at the 24 ram chips because undoubtedly that's the only time people's hands get unsteady and they wind up destroying numerous ram components. choose another chip close to the headers, that's how you will determine where your +5 is at. your game appears dead, so I'm going to venture a guess that the voltage is morbidly low.

also verify that you have 3 capacitors by the power plug on the MPU, 100 uF/25V. if they're somehow missing like they were on one of my boards then you will have no voltage going to the chips. :)

the power plug has a variety of different colored wires, this is where you can obtain your reference voltage for the +5 at the grey wires. you can also sample the grey-yellow and grey-white (regulated and unregulated +12) and grey-green (-5) too. the ground is the black wires.

the Williams guide in my signature is usually somewhat helpful, but your game looks completely dead. please take pictures of the actual power supply showing how the wires are connected to the lugs, and take pictures in sections of the MPU board, so I can see if you're missing any chips.

also make sure the monitor has a video signal coming into it, they'll be purple wires, and they connect to the middle big plug on the MPU. and last, from a diagnostic standpoint, the rom board will show all 4 LEDs because the MPU is probably not working at all.
 
I have test voltages on the switching power supply. They are right on. Next i tested at the harness connector shown below and got nothing.


I also turned down the fly back here is the picture.

I guess the harness could be bad but didn't notice anything. I will take a much closers look when I have more time. I have the also included the pics of the entire boards. The 3 caps are there. What else should inspect other than the harness?
 

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Additional pictures
 

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It does not appear that the original linear power supply is powering your boardset from your pictures - only the coin lights and coin door.

Again, from your pictures, your switcher is completely powering your boardset and if your switcher is dead on, then there has to be power loss in the wiring or headers somewhere. You said that you tested the switcher? Did you test all 3 voltages? You should be getting +5vdc, +12vdc and -5vdc on the corresponding switcher terminals. The 4116 RAM that defender uses needs all 3 voltages to run properly.

Report back the voltages that you are getting..
 
Obviously you know, the game is dead. It isn't booting (no rug pattern) or even trying.

From your description, I'd be testing from point to point (power off) on your harness, looking for where you have the problem. You either have an open, or a high resistance connection. This is tedious work - to keep you from getting confused, make a table of every wire in the harness (start with the power connector) by color code, and keep track of everything you find.

Good luck! Defender is a game worth getting working. I have a Stargate that works.
 
i will try that. i am planning on doing a continuity check on the harness going thru each wire. i am gonna throw the pcb in my other defender next to see what it does with it. maybe i can get some more info that way as well
 
people keep neglecting the capacitors on the MPU are old and you lose a ton of voltage between them. yours would have to be monumentally bad, cause I've seen these games with dinged caps boot and somewhat play at 4.2V at the chips. :)
 
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