Galaxian IC's

kpkube

Member
Joined
Dec 12, 2010
Messages
899
Reaction score
19
Location
Valencia, California
What would be a good list of IC's to have on hand for a Galaxian and Ms Pacman board repairs?
Which ones are the most common ones to fail?
 
Z80CPU, 2114 ram, 93422(2101) ram, LM1877, LS161, 7489 ram, sockets, LS245, LS377, LS158, LS159. A good assortment of all the common ttl and ram should be in your tool box if your going to work on pcbs.
 
Z80CPU, 2114 ram, 93422(2101) ram, LM1877, LS161, 7489 ram, sockets, LS245, LS377, LS158, LS159. A good assortment of all the common ttl and ram should be in your tool box if your going to work on pcbs.

Don't forget the one's I need to fix addressing issues 74ls138.

That z80 should be a z80a for Galaxian.
 
Can't believe you're forgetting 2532 EPROMs!!!

Get some sockets too. 24, 28, and 40 pin.
 
Now if Riptor was a parts guy; he might just put some of these together as a kit of some kind at a good price.
 
I don't put kits together for those as it's FAR easier to bridge traces and pull traces off of Pac boards than Galaga.

Also, the same flat resistor packs that are such a problem on Galaga just aren't the problem parts as they are on Galaga boards.
 
Yep, they rarely used those crappy resistor networks on the pac boards. Although some do have them I dont think they take the abuse like they did on galaga because of their location.

For you guys wanting kits I just added a "build your own kit" app on my website. We call it a "shopping cart" ! :)

Yeah eproms are a given especially on pac boards.
 
Last edited:
Yep, they rarely used those crappy resistor networks on the pac boards. Although some do have them I dont think they take the abuse like they did on galaga because of their location.

For you guys wanting kits I just added a "build your own kit" app on my website. We call it a "shopping cart" ! :)

Yeah eproms are a given especially on pac boards.

How about I come by with about 5 crappy Galaxian boards to your place and Frankenstein one good board that will roam the earth endlessly. Or I can keep you in business for the next year or so just buying parts I may need some day.
 
How about I come by with about 5 crappy Galaxian boards to your place and Frankenstein one good board that will roam the earth endlessly. Or I can keep you in business for the next year or so just buying parts I may need some day.

I will be around all day tomorrow.
 
Using the list in this thread, i placed my 3rd order in a week with TwistyWrist! Maybe this set will allow me to get a working Galaxian board!

thanks for the detailed list, I've started my 'toolkit' chip collection.
 
Using the list in this thread, i placed my 3rd order in a week with TwistyWrist! Maybe this set will allow me to get a working Galaxian board!

thanks for the detailed list, I've started my 'toolkit' chip collection.

What is the problem with your Galaxian board? I just got one going at the End of Line Arcade Party with the help of Buffet and parts from Riptor.

In my case the z80 was stuck in watch dog. I burned new roms and replaced the 74ls138's with no joy. The problem was the 74ls245, replace it and board boots and plays fine.
 
Board is now booting, and coins up and plays, but most of the active or bottom 1/2 of the screen is jittery or mis-drawn. Letters seem to be split on both sides of their bounding rectangle, ships shudder, etc. There are so many ICs on the troubleshooting pages that start with 'game plays', it is hard to know exactly which chips to buy to attempt a resolution.

here is a burning question: I have seen Mr Do function properly when 'piggy-backing' ram chips on top of the ones on the PCB - is it valid to assume that piggy-backing works for any/most bad chips, or is this technique only useful for a subset of the problems exhibited by bad soldered-in chips?
 
Piggybacking doesn't work with the pin on the chip is shorted internally to +5 or ground.

One good technique is to run your fingers along the pins of the chips to see if the screen goes bonkers when you touch a specific one. The capacitance of your finger is enough at times to trigger bad pins on the chips. I've done that many times to narrow down a problem on a board.
 
The finger test showed nothing.

I think I'll replace the 273 at 4L next, as the troubleshooting description says 'effects horizontal position' - when ships start to dive the whole ship collection shifts to the left and wraps around to the right side of the screen.
 
You don't need to blindly change chips out if you have a logic probe.

For an LS273 refer to the data sheet. There is a clocking pin, a clear pin, and inputs/outputs along with power and ground. Verify power/ground with the logic probe then verify clock. If there's no clock then the chip does nothing.

Next verify that clear is either high or pulsing. If it's low then the chip will output nothing.

http://www.ti.com/lit/ds/symlink/sn74ls273.pdf

If the clock and clear pins are correct then you'll get outputs. Check the input pins and the respective output pins. You may have a stuck input or output. Stuck pins aren't always indicative of a problem with a specific chip. The chip it's tied to may be bad instead. Keep that in mind.

RJ
 
You don't need to blindly change chips out if you have a logic probe.

Thanks for the prodding - i have an unused probe and have been trying to learn what it can tell me.

After seeing the Pac glitching posting, I checked the voltages on my board. At CP26 it reads 4.97, middle of col #4 is 4.95 and middle of col #1 is 4.94. Is this too low? How do I get it higher? I am using the original dual-transformer AC power supply.
 
Last edited:
I wouldn't sweat 4.94 volts on a Galaxian board. There is no adjustment to the power supply on it either.
 
video of display issue

Anyone have an idea on what is wrong with this board?



I've replaced all the socketted RAM, cleaned and reseated the daughter board. Also replaced the 2101 RAM with sockets and fresh chips (this made a difference in the video issues, but was before the video was taken). I've replaced 3 other chips (3L, 2K and 4L), falsely identified by my logic probe experimenting, but nothing makes a difference).

thanks for any ideas on where to look.
 
Last edited:
My problem is resolved!!!

A package of love showed up from Bob Roberts today, including some 2101 RAM chips. swapped then onto the board and it plays perfectly.

Now to talk to the seller of the bad chips...
 
Back
Top Bottom