Galaxian vertical lines issue

animesuperj

Well-known member
Joined
Oct 26, 2009
Messages
2,132
Reaction score
104
Location
Mukwonago, Wisconsin
Posting this in the correct section this time. Sorry for any confusion before.

I just picked up a Galaxian cab this weekend, and it has vertical lines for everything on the playfield. Any idea what might cause this? It also looks like the images are doubled. Is this is the case as well, or is it just related to whatever is causing the vertical lines?

main.php


main.php


main.php
 
Did you first confirm the voltage on the cpu board? Test on the .47Mfd cap on the edge of the board by the 3 prong connector. Make sure it is around 5.2 volts DC. The 2147 video ram chips are a common failure that cause vertical lines in some or all of the graphics. Try reseating them and switching them around to see if this helps.
 
Did you first confirm the voltage on the cpu board? Test on the .47Mfd cap on the edge of the board by the 3 prong connector. Make sure it is around 5.2 volts DC. The 2147 video ram chips are a common failure that cause vertical lines in some or all of the graphics. Try reseating them and switching them around to see if this helps.

Galaxian doesn't even use 2147s... it uses 27ls00s for the sprite line RAMs.

If it were the line RAMs, it'd only effect the sprites, and obviously the background characters are also affected.
 
Sorry, somehow when I read this my brain registered galaga. I guess I shouldn't post past 10pm. But the rams in my spyhunter affected background as well. When I moved the bad chip the cars were no longer the problem, the background was. Anyway, it couldn't hurt to check out the ram.
 
I'll check out both cap and the ram. It's at least somewhere to start with the issue. Thanks for the help! I'll post the results once I test this out.
 
I haven't worked on a Galaxian for a while, but from memory I'd say it would be a good idea to start at the LS161's in the bottom row and, using the schematics, work up from there.
 
Check the 2 EPROMs along the bottom of the board.
 
Tactful as usual.

I'm simply stating where I would start troubleshooting a board. The EPROMs are easy to check with a programmer - read them and verify the checksums with ROMIDENT.

This way he can be sure that he won't be chasing his tail around trying to find problems in the soldered in chips when the EPROMs may also be corrupt.
 
Tactful as usual.
Considering I already gave him the answer in the other thread, I don't know why this one even exists.

I'm simply stating where I would start troubleshooting a board. The EPROMs are easy to check with a programmer - read them and verify the checksums with ROMIDENT.
You have an eprom burner... he likely doesn't... why worry about the ROMs when they obviously aren't even being addressed correctly at this point? Might as well have him recap the monitor too at this point, just to make sure that's not the problem =-P
 
Have you tried recapping the monitor?



:p



We have a Galaxian that's starting to do this, would be great to have you figure out what's doing it and save me the trouble. :)


BTW: That recap the monitor thing... that was just to piss with Hudson.
 
I have not recapped the monitor, lol, and also understand it was just a joke. I'd prefer to not piss anyone off, even if Hudson isn't very verbal in his posts. Yes, it'd be great to hear more that he might know, but even small points on where to look to fix a problem will help me. I'm still new to fixing problems, and am working my best to learn as much as I can. I'm not saying no to any help, even if it is something short.

Also, as Hudson has guessed correctly, I do not have an eprom burner; so It's probably going to be tough to verify checksums.

I will try checking what people have stated in this thread, and what Hudson said in the previous one. Thanks again for any help anyone has provided.
 
I have not recapped the monitor, lol, and also understand it was just a joke. I'd prefer to not piss anyone off, even if Hudson isn't very verbal in his posts. Yes, it'd be great to hear more that he might know, but even small points on where to look to fix a problem will help me. I'm still new to fixing problems, and am working my best to learn as much as I can. I'm not saying no to any help, even if it is something short.

Also, as Hudson has guessed correctly, I do not have an eprom burner; so It's probably going to be tough to verify checksums.

I will try checking what people have stated in this thread, and what Hudson said in the previous one. Thanks again for any help anyone has provided.

Yeah, there is a way to get more specific information out of Hudson... ... water boarding. That's pretty much the only way. lol

He'll point you in the right direction though, it's all about going from there. He's helped me several times. Because of that I now have a HUGE stack of printed datasheets on pretty much every chip on every board I've ever had...
 
I have not recapped the monitor, lol, and also understand it was just a joke. I'd prefer to not piss anyone off, even if Hudson isn't very verbal in his posts. Yes, it'd be great to hear more that he might know, but even small points on where to look to fix a problem will help me. I'm still new to fixing problems, and am working my best to learn as much as I can. I'm not saying no to any help, even if it is something short.

Also, as Hudson has guessed correctly, I do not have an eprom burner; so It's probably going to be tough to verify checksums.

I will try checking what people have stated in this thread, and what Hudson said in the previous one. Thanks again for any help anyone has provided.

To clarify what I suggested, check the outputs of the 74LS161's/74LS163's at locations 3A, 4A, 5A, 6A (outputs on pins 11, 12, 13, 14, 15) - if they are okay move onto the 7486's at locations 5B and 6B (outputs on pins 3, 6, 8, 11) and go on from there.

Schematics can be found here:

http://arcarc.xmission.com/PDF_Arcade_Bally_Midway/Galaxian_Troubleshooting_Guide_Part_2.pdf

At the end of the PDF document.
 
Well, let's start on the simple side...

Do you have a logic probe or oscilloscope to check the signals with? If not, get a logic probe with audio capabilities. Otherwise you are simply desoldering and swapping out chips blindly.

RJ
 
Good point, I was assuming that he at least had a logic probe, I don't think he should be swapping out chips (not until he has identified the dodgy one). :)
 
You shouldn't even need a logic probe... you should be able to look at the screen and see that at least 2 vertical count lines aren't toggling / making it through the xor / muxes, and identify which ones they are.
 
To clarify what I suggested, check the outputs of the 74LS161's/74LS163's at locations 3A, 4A, 5A, 6A (outputs on pins 11, 12, 13, 14, 15) - if they are okay move onto the 7486's at locations 5B and 6B (outputs on pins 3, 6, 8, 11) and go on from there.

Why would you tell him to check 3A and 4A when the H count is fine?
 
Back
Top Bottom