Repair Logs

Galaxian (Midway) PCB repairs

01/27/2000

Tools: soldering iron, solder wick

Problem: Garbage on the screen - a mesh of horizontal and vertical lines with a few random alien sprites

The legs of the RAM at location 1-P were broken off in the socket, and the IC was missing.. I desoldered the socket and put in a new one. No change when the board was powered. Touching the tops of different chips, 5-K was really hot. It is a 74LS245. This one was already socketed. When I removed the chip I noticed it was in the socket backwards. No wonder it was getting hot! A new chip was installed and the board was fixed.

NOTE: The chip at 5-K looked as though it was installed correctly, but the correct orientation was with pin 1 in the opposite direction of the chip next to it. Always check the notch on the chip and match it to the socket when installing it.

Solution:

• Fix socket and install RAM at location 1-P
• Remove and correctly install a new 74LS245 at location 5-K

12/03/2001

Problem: Game plays but no sync

Solution: Replace bad 74LS08 at 64

12/03/2001

Problem: Game plays, screen looks smeared, enemies are red blobs

Solution: Replace bad 2101 Ram at 4F

12/03/2001

Problem: Game keeps resetting, test mode shows bad rom

Replacing the rom board made little difference. The sockets had been replaced on the main board before with cheap single wipe sockets, so I put in a new set of dual-wipe sockets, replaced the rom board and it fired right up.

Solution: Replace bad sockets at 7F and 7J

12/03/2001

Problem: Color on the Flagship was OK during attract mode, but during game play it was red instead of yellow.

I figured this was a ram problem so I started swapping the 93421 rams in row 1. Changing them out one at a time and testing the board again, I finally replaced them all and still no change.

I decided to check the character roms. When I reseated the 2716 character eprom at 1K/L and the problem was cured.

Solution: Bad/dirty connection on eprom 1K/L, a 2716 character eprom

01/31/2002

Problem: Dead board

Board was completely dead. No signs of life. First I checked the crystal for a pulse with my logic probe and got nothing. Looking at the schematics I found that the LS368 at 1E is in the clock circuit next to the crystal. I've usually found that if the crystal does not have any broken connections, the chip that the crystal feeds is stuck either high or low killing the output of the crystal. This was the case here. I replace the LS368 with a new chip and the board came back to life.

Solution: Bad 74LS368 at 1E