ArcadeCollecting.com
Welcome, Guest. Please login or register.
June 18, 2019, 06:48:24 PM

Login with username, password and session length
Search:     Advanced search
Yay, a message board!
319 Posts in 114 Topics by 43 Members
Latest Member: deejaymc
* Home Help Search Login Register
+  ArcadeCollecting.com
|-+  General Category
| |-+  Repair logs
| | |-+  Defender
« previous next »
Pages: [1] Print
Author Topic: Defender  (Read 2337 times)
tim
Administrator
Full Member
*****
Posts: 166


View Profile
« on: November 20, 2005, 04:38:20 PM »

Symptoms
Game boots into rug pattern which repeats forever.

Tests
Pulled and tested all ROMs. The three old, gold-legged ROMs had broken legs. Replaced. No change.
Examination of CPU board shows signs of battery acid damage. Lots of green powder on and around
RAM sockets. Pulled all RAM and replaced with known working RAM. No change. Random probing of pins
of RAM chips with logic probe show lots of floating address/data pins. Replaced 12 of the 24 sockets.
Now all pins show nice pulsing and rug pattern looks better but it still never gets past it.
The pattern is not wiping across the screen normally.

Instead of scrolling smoothly from right to left like this:

--------->|

It draws in two columns, like this:

----->|-->|

I post these results on rgvac and am told by two people to check the 74153s. There are four of them.
Poking around with a probe, they all seem to be pulsing happily. One, however, has slightly different
sounds to the pulsing. There is a bit of corrosion on the pins. I pulled it and tested it in the
Allmax. No good.

Fix
I pull a 74153 from my bootleg Defense Command, pop it in and the game boots. Initial
tests indicate, unit ok.
Logged
Pages: [1] Print 
« previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!