Defender repair log

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Expand view Topic review: Defender repair log

by Tdarcos » Mon Aug 14, 2017 1:13 pm

Ice Cream Jonsey wrote:(And it is a dream to work on, big giant spaces, easy-to-get-to boards, exact opposite of Taito.)
I've seen the same thing in the PC world. Hewlett Packard desktop PCs almost always use clips or thumbscrews, everything can be taken apart and parts replaced without tools. Sony Vaio desktop PCs, on the other hand...

by Jizaboz » Mon Aug 14, 2017 9:20 am

Nice! Good job dude.

Defender is one of my favorite games. Wish I owned the real thing like you do. My buddy Scott had his freak out on him last month. Booted to RAM error.

About a week before that I noticed the screen would sometimes do this quick glitchy flash on occasion.. especially when a lot of shit is blowing up in the game.

by Ice Cream Jonsey » Sat Aug 12, 2017 4:03 pm

Annnd fixed, it appears. (If this was a Taito game, it breaking again 25 minutes later would stop me from having any sort of confidence.)

So, to run the RAM test, you have to have the one "manual" test switch, which is black, depressed when you start the game up. Get into the RAM test.

RAM test said 12 was bad. This post from gamefixer (who also saved my Spy Hunter in person before he moved to Texas, great dude)

https://forums.arcade-museum.com/showpo ... stcount=10

Said that it's just bank 1 chip 2. Cool. As far as I can tell, the Defender boards aren't labeled anywhere, so the "4M" that the manual speaks of is not helpful information.

Swapped that chip out for a new 4116 that I had picked up somewhere along the way. Glad I had it. Defender started right up again.

Defender was produced in 1981 and the original chips were all there. So that's 36 years? I guess one chip failing after 36 years is OK. (And it is a dream to work on, big giant spaces, easy-to-get-to boards, exact opposite of Taito.)

Defender repair log

by Ice Cream Jonsey » Sat Aug 12, 2017 12:00 pm

Just keeping track, as it was like a year for Tempest and Zoo Keeper and I am not doing that gain.

Started Defender today and got "Initial Tests Indicate RAM failure."

Figured out that I can't adjust the +5 on the Defender power supply. (It can be done with a mod.)

So first steps:

1) Ensure the right voltage is getting to the 4116 chips
2) See if I have any others
3) If so, identify the bad chip and replace it
4) If not, order some 4116 RAM chips

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