Archive for the ‘Bally/Midway’ Category

Dead Gorf

Sunday, October 4th, 2015

So I found a dead Gorf on Craigslist.  It was an older ad, but was still available when I inquired.  Dude I picked it up from had done some pretty impressive restorations on some other games.

Anyway – it was dead alright.  Shows a blank screen that looked overly blue due to how the monitor was adjusted, no starfield was visible.  Slid the test switch over and power-cycled, but this made no difference either.

The previous owner had mentioned that he had done some work on it.  I saw some of his other previous work on other boards of his and while not perfect (some cold joints, or not enough solder in some places leaving “pits”), it was not horrible and definitely no worse than what I was doing when I started out.

Anyhoo, starting with the power PCB – the previous owner said he had already replaced the caps, but I wanted a second look at it, JIC.  On the solder side of the board, some larger traces has been lifted off the board during some previous repair work (I do not think it was his, maybe someone before him?).

It looked like the someone used a serious soldering gun to do the work, because there were scorch marks on the board(!) and flux was all over the older work too.  Continuity was where it was supposed to be, so I guess that while it was ugly, it worked.

Hit the previous work with a small wire brush to clean up some of the flux, and reflowed solder on it and the connector pins, just to be safe.  While I was doing this I noticed that an IC had two pins soldered together, but each pin had its own separate trace, which looked suspect.  Verified with the schematics that the pins are NOT supposed to be soldered directly together and fixed it (they are actually supposed to be connected through a fuse).

Powered the game back up and it came up with a rolling screen but I could make out score displays at the top.  Also was showing some solid “blocks” that made me nervous and some color distortion.  Was able to get the screen to lock with a simple monitor adjustment.  Blocks were just the test screen – I had forgotten that I left the test switch closed.

Game was already set to free play, so I started a game.  Immediately noticed that some sounds are missing, and no speech.  Adjusting volume controls did nothing to fix it, but I quickly determined it was channel 2 that was broken.

Checking voltages at the channel 2 speaker shows it at a constant ~14 volts!  Metering the input to the amp board shows sensible readings that change while the game is running, so I think the input is good.

Taking the amp board out and metering the transistors shows some strange readings, but they were in-circuit.  Swapped the two audio lines at the connector (pins 4 and 6), and I was able to hear the other set of sounds, but still no speech.  After paying closer attention, I noticed that I was getting a a click or two when I was supposed to be hearing speech.  So I think I verified that the channel 2 section of the amp is bad and  the Votrax SC-01 is bad, too.  That last part really IS bad, because they are not easy to find!

Decided to shotgun the entire channel 2 section of the amp board, JIC – this is old hardware, after all.

After doing that I remembered I forgot to actually check the speaker itself.  Sure enough, it was supposed to be an 8 ohm speaker, but it was shorted.  Replaced the speaker and connected up the repair amp board and now I have all sounds except speech.  The mother ship explosion never sounded so good! 🙂

The SC-01 chips are getting hard to find and are a bit pricey.  But I do want the game working fully again, so it might be worth it.

Update: Purchased an SC-01 from GameRoomRepair.  Installed and Gorf has its voice once more!

Cook Race (bootleg Burgertime)

Saturday, October 11th, 2003

Some sprites are missing, but still in the game. For example, when you throw the Pepper, it is not drawn on the screen, but it still stuns the bad guys. One or two of the bad guys are also invisible, so Peter Pepper can effectively get killed by nothing!

Game does not draw garbage where these graphics/sprites should be, they are just never drawn at all, and they do not disrupt the background graphics (i.e. they are completely transparent) so I do not think that it is a ROM or RAM problem.

Not knowing too much about this kind of problem, my first guess is that the specific sprite(s) are not getting their data placed in the appropriate spot when it comes time to draw the required sprites. For example, they are not getting selected by a latch that determines if it should draw the sprite’s colors, or draw the background (in transparent parts of the sprite). So into the schematics I go…

Solution: None yet.

Update #1: Well, fat lot of good that did. I could only find schematics for Burgertime, and not even the cassette version (which the Cook Race hardware seems to follow) for that matter. This one is starting to collect dust on the shelf.

Update #2: David Widel said on his web page (www.widel.com) that he was looking for a Cook Race board. I contacted him about it and he said that he would be interested in it so I gave it to him. Better to further the arcade/multigame cause than to have it sitting on my shelf collecting dust.

Galaxian – “Dead”

Thursday, April 17th, 2003

Purchased described as “dead”. Started by creating a JAMMA adapter (I hate creating adapters, it is tedious work). Well, the description was correct – she is dead alright: screen has static garbage and required some tweaking to sync correctly on my test bench monitor.

Watchdog is barking, disabling it has no effect on the screen’s contents. Board already had some previous work done in it, solder-side contains more than 20 jumps to connect some RAMs back onto the bus. The Parts side shows the missing/removed/blown traces being jumped.

Started by checking the daughterboard, seems OK. Next I remove, socket and replace the 74LS245s on the board because word has it that they tend to be the cause of most problems, the Galaxian Trouble Shooting Logic Board manuals lists similar symptoms connected to those chips, and the Fluke 9010 troubleshooter says that the address lines are tied. Other than that, I cannot come up with a good way to check them! 🙂

Gotta wait for some replacement sockets and chips to come in…

(more…)

PAC-MAN (Midway, single board)

Wednesday, February 12th, 2003

Board 1


Flashing “1” in corner of screen. Took a look at the Pac-Man troubleshoot by picture guide and that pointed me to “4R video RAM bad”. Swapped it, no good!

Tried swapping other RAMs, no change either. Started pulling all socketed chips and found a bent pin on the ROM at 6E! straightened it, and reinserted, Pac lives once more.

That will teach me to try the simple checks/fixes before the more complex ones…

Solution: Fixed bent pin on a ROM chip.

Board 2

Game would boot normally, but would then start getting random lines/glitches through the screen after running for a couple of minutes; they did not otherwise effect gameplay. Immediately suspect video RAMs, start hitting ’em with the freeze spray and sure enough, got a bad one. Replaced it, and all is well!

Solution: Replaced bad RAM chip.