Astroids pcb repair

MartyMcfly

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I've been repairing this Asteroids board on and off for the past year.

The image currently has wavy lines.

The first thing that I noticed when I got the board was 3 transistors (at K10) were the wrong type. I had some NOS so replaced them.

I broke a couple of legs from two IC's when I was cleaning them. They were pretty brittle. I fixed them.

Asteroids Deluxe works fine in my test machine. This board however shows traces in addition to the wavy lines. Even turning down the brightness all the way down doesn't help.

I researched here a bit but couldn't find what DAC means.

Anyway, as I'm taking pictures I could see the image scrolling vertically though the camera's screen. I plugged in Asteroids Deluxe just to make sure and it has no scrolling.

So back on the work bench I started looking at anything wrong near and around the X Y section of the board. All I can see is corrosion on the clock at A12 (940 TL082CP). I'm wondering if that be the problem.

Any ideas?
 

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Looks to be an issue with the Z circuit, which provides the blanking of the beam between objects.

Try checking/replacing the LS164 at K9 (or K10), and then the LS04 at H10 (H11), as well as Q1, Q2, and Q3. (The exact locations will depend on which rev of the PCB you have.)

See the schematics for more (and make sure you have the 7th printing, which are the newest ones). The Z circuit is on the last page.

Also, DAC stands for Digital to Analog Converter.
 
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