Defender boot up RAM error

PrairieDillo

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I just got this free defender. electronically it looks very complete and clean inside... the outsides are a totally different story.

Please help me figure out where to start trying to get this machine repaired.
Thanks for any help. The board sets seem nice and complete. Lots of stickers are still on the chips.
 

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My first Defender had a ram failure similar to yours. There is some sort of code you can decipher with the LED lights on the board to find out which one it is, but chances are more than 1 chip is bad. I replaced all the 4116 RAM chips (from coinopchips.com) and never had a problem ever again.
 
howdy! firstly, if you dont have the schematics and manuals, grab these off the net: http://www.robotron-2084.co.uk/manualsdefender.html

the first manual, "Upright Instruction Manual
(Early Series Boards)", contains a section on how to interpret the led lights on the board. post a little more info about what lights are showing up.

to do this you will need to open the rear door to access the boardset, and, you will need to pull out the interlock switch so you can still run the game with the door open. make sure you dont go near or touch any live mains wiring. around the power supply or interlock switches or the monitor.

there is also a section in one of the manuals about setting up the game using the switches on the coin door. these are the switches referred to in the first manual.

having interpreted the leds to see which rams are referred to as possibly faulty, next step will be to run through a series of checking & cleaning operations.

do you have multimeter ? if so, you should check the dc output voltages from your power supply - the 5v rail, 12v rail, & -5v rails in particular.
next step, measure the voltages at each voltage input on some of the rams which will tell you if the rams are etting the right voltages or not.

if the voltages are low you may have some problems with the power supply so that is a good place to start checking (having turned off the system first of course)
- each power supply pcb wiring header connector on the power supply pcb for signs of overheating, corrosion, cold or cracked solder joints and dirty header pins, or dirty wiring plug socket connectors.
- reflow solder on the header pins, clean the pins with a brillo pad (the green scourers) and then some metho or electrical contact cleaning spray (radio shack ?)
- you could carefully remove each ram - use a fine flat screwy to lever up evenly being very careful not to bend any legs, carefully clean the legs with the same above and reinstall each ram ensuring the legs go in straight and dont fold under or bend.

post up your results!
 
thanks guys... yes I have a fluke multimeter...
good info and very clear!!!!

Sounds like a very solveable problem!
 
Boot it, and use the coin door switches to get into diags. Run the RAM test, it'll tell you which chips are bad. You'll get a number like RAM 14, which would be bank 1, chip 4.
 
Thanks guys

I ran the RAM test and got the error code

RAM FAILURE
RAM 22

The first of the four LEDS was lit.

X 0 0 0

Reading the manual and trying to figure out how to read which bank it is now...
 

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from the manual I'm thinking reading that it's this chip that needs replacing...
I'll try cleaning the legs on it.
 

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from the manual I'm thinking reading that it's this chip that needs replacing...
I'll try cleaning the legs on it.

That's the one. If cleanup doesn't fix it, swap it with another chip. If the error follows the chip, the chip is bad. If the error stays at 22 the socket is probably bad.
 
you guys are just great!!!

I replaced it with a chip from a water destroyed defender I had. the Chip was really corroded but I polished the pins and dropped it in.

PRESTO... this jacked up defender LIVES!!!!

Thanks for all of the help.
 

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Looks like you still have some RAM junk on the right side of the screen. You might need to reseat the other RAM chips if it doesnt give you a RAM failure anymore. Heres what mine looked like:
 

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Looks like you still have some RAM junk on the right side of the screen. You might need to reseat the other RAM chips if it doesnt give you a RAM failure anymore. Heres what mine looked like:

He just needs to stretch the horzontal width out to push that off screen.

ken
 
That works too :p

IIRC, that line comes from a bit of the video RAM that's used as scratch memory, so it's there on every Defender and it's supposed to be adjusted off screen. If it has a G07, just tweak the width coil (carefully with the proper plastic tool so you don't kill yourself) and it should be fine.
 
Yup, I have all the right tools. I'm putting a list together for bob to get a full kit for the monitor. I'd like it all freshened up. I just got a Rejuv also so I'll probably check the tube when I figure it all out.
 
Boot it, and use the coin door switches to get into diags. Run the RAM test, it'll tell you which chips are bad. You'll get a number like RAM 14, which would be bank 1, chip 4.
hi just fyi, what is the coin door switch... to goto diags... i mean i still need to get past the power on rug screen, but when i do what is this technique?
thx
 
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