What fixed your game today / general repair log

Pulled my Astroids out of storage today and it had an intermittent restart issue. Wow it's been a long time since I worked on any arcade games so had to relearn. Started from scratch with checking voltages, big blue, etc. then pulled the board out and started checking stuff. Pulled out the socketed chips, cleaned, brushed with Deoxit and put them back it. Game works fine now.

Michael
 
Another Star Wars..
1st problem - Audio board would constantly reset. You could hear a regular cadence of click-click every second or so.

I know that the Audio board boots up and does a self test and then reports that back to the CPU board. If the CPU board doesn't like what it gets it will reset the sound board until it get's what it wants. This game has a Vector Labs multi kit in it and has LOTS of replaced chips from previous repairs. Here's what I did:
  • Removed multi kit and stuffed board with SW sound ROMs. Board still reset.
  • Placed all the socketed chips in a known good board. All good.
  • I noted that the 40 pin sockets for both the CPU/PIA were seriously janky/worn out and one of the previous repairs had a damaged socket. So I pulled all of that and replaced them. Still stuck in reboot cycle. The 16 pin pads were a bit messy from the previous work. I was able to validate all connections and get a new undamaged socket in there.
1709989546839.png1709989491048.png1709989458331.png
  • A pretty common problem here is the Speech Synth clock (+5 to -5v signal) can go bad (4096) and that will cause this. Oscope showed super clean signal.
  • Probed around the board but all control signals looked good.
  • Figured the likey cause was the CPU/Sound buffers. So I pulled out the HP1660CS
  • Found that the Sound to CPU buffer was bad. Replaced this (LS374 @5K) and working.
1709989224185.png1709989413932.png
You'll see bit num 5 stuck high on the output to the CPU. Up top is the write into the latch and at the bottom is the read. It expected to see 01011010 but got 01111010. There was a lot of extra cycles in between but I use the LA to only store 10ish states around each Write/Read.

There was also some work on the Main PCB that was described in this series of posts which ultimately were some errors with the kit and with it's installation.
 
Asteroids sound problems
10 months ago, I turned my Asteroids on which has a multi kit installed and found out all my sounds were cutting in and out and I was missing the thrust sound, and the explosions were digital pops or clicks. As I started troubleshooting the board the sounds started working except for the thrust and explosions but I pulled the op-amp at P12, and it tested bad, so I installed a socket and installed a new LM324. That fixed the first problem which is in the Part 1 video. In Part 2 I figured out both the missing explosions and thrust was due to the noise generation which is produced by R10 and P10 both are 74LS164 shift registers It turned out both the 74LS164's were bad and replacing them fix my sound issues. If you want to see how I fixed the sounds the 2 videos are listed below.
 
Frankenstein Defender cab running a JROK and Moon Patrol stack via a JAMMA switcher. WG 19K7203 monitor started glitching when shooting boulders in MP, it had been losing sync after being on for 20-30 minutes previously. Eventually sync would go out completely. I surmised the loud, low frequency rumble sound of the boulder explosions was vibrating a solder crack in the sync pins, which were going out anyway once the board got warmed up; loss of sync was consistent across both boards.

Pulled the chassis, sure enough the sync pins had visible solder cracks. Reflowed all the input pins and did a 45 minute test, no issues. Packed everything back up and declared victory.
 
we have a Star Wars Trilogy at work where the Y-axis of the joystick just kind of went on strike. if you tried to play the game and got a little aggressive with the joystick it would go hard bottom or hard top. it's not a dedicated cabinet, I couldn't remember how to open it, but once it was open I looked at this interface board and immediately set to jiggling the plug going into it back and forth. observed it was a little too flexible. getting it out and into a room that actually had light revealed that my theory was correct... the solder cracked. (this is an example of solder halos I speak of often lol)

resoldering this header and putting the board back in the game had me blasting Stormtroopers in Echo Base again. I forgot how awesome this game was. I was really just thankful I didn't have to pull the whole joystick out cause that would've been a laborious and awful task.

20240325_161046.jpg
 
Friend sent me his Asteroids board. Had an interesting failure..


The Asteroids roll off the screen on the right and stretch back to the left side. At first it looked like an analog section issue. I replaced the 7915 and 7815 voltage regulators just to be sure. They were original and I've seen weird issues with them in the past. It was low probability and not the issue.

Once I paid a little closer attention - it was clear that the issue was very specific to the vector moving off the screen and it was some sort of carry over issue.

image-7.png
Thank you Atari for the excellent detail, saved me a little time looking for the carry over issue..

image-8.png
In this specific case, the 74191@C9 (not an LS191 on this particular board) had a grounded/shorted output on PIN6-UNMDACX11. Interestingly the carryover bit on PIN7 was working just fine..

Replaced with a 74LS191@C9.
Board works!
 
I bought a Midway Space Invaders Deluxe almost two years ago and started working on it a few months back. Game would not boot, and only got to the score screen and then reset. Had to burn a test ROM and strapped the board to accept 2716's. Test ROM passed everything. While using my scope I shorted something on the main board that took the game down completely. Not knowing what I blew up I decided to send the board to Sean at Classic Arcade Repairs. He found I had blown the 3245 intel chip. He replaced that chip but game still wouldn't boot. He tested the daughter board in his game, and that was found to be working, but he didn't check the sounds. He was thinking that it had a flaky RAM chip that wasn't showing up. I opted to have the board set back to me now that I knew the daughter board was working. I removed and tested all 16 RAM's, they tested good, but decided to just replace all of them. Game still wouldn't come up and my fluke was showing a DCD error on bit 8. Bit 8 comes from the LS157 at F6. Replaced F6 and game came back to the original problem of only booting to the score screen, then resetting. My comparator kept showing outputs on the LS153's at A2-D2 were not what it should see. I hate doing this, but I started pulling and testing them one at a time. A2, B2 passed in my tester, but C2 failed. Replaced C2 and that made the board come to life. I put the board in my cab and found only the invader hit sound was missing. I looked on the schematics and saw K4 & K5 LM3900's control the sound. Replaced K4 and still no invader hit. I did try piggybacking K5, but still no sound. (As we all know, this doesn't always work.) Decided I had nothing to loose by replacing K5, that's what I did......that fixed it. Thanks to Sean for narrowing down what board was the issue, not sure I could have figured that out, without a working main board. Also thanks to wugly for sending me the schematics and the link for the test ROM. If anyone is wondering I did burn new game ROM's using 2716's. I had no way to test the original ones
 
I spent the weekend at @Dillweed's this past weekend. During that time I helped get a handful of his games working. Here's the logs.

Game: Williams Defender
Symptoms: some controls not working
Solution: disconnected ground wire on the control panel

Game: Midway Galaxian
Symptoms: stuck tone in game, really loud. Missing shooting and explosion sound
Solution: Bad LM324 at 7S

Game: Atari Asteroids
Symtpoms: dead. Y deflection issues on the monitor
Solutions: added missing 12.96MHz crystal. Replaced both Y deflection transistors as the ones in there were shorted.
Note: the game board was not the original one to the game, the one that was in there was long gone. My guess is that the original board went haywire and gave a Y signal that the monitor couldn't handle, killing the deflection transistors.

Game: Sega/Gremlin Borderline
Symptoms: not booting, flakey
Solution: pushed in/damaged pins on the power connector to the game board. Replacing them resolved the issue.

Game: Exidy Robot Bowl
Symptoms: Dead short across 5V and Gnd, locking up/not starting a game after removed short
Solutions: short was caused by bad 7404 at 9F. I identified the short by manually rigging from a modern supply. The 04 popped abd identified itself as the culprit. After that, the game would not start. This was a bad 74ls367 at 1D.
 
here's another free tip. Spy Hunter at work apparently had a history of the steering wheel going 360 degrees, and with wiring harnesses inside you can only surmise what that does. bunch of wires broke off the female source side plug, but I couldn't even see the wire colors on the male side plug from the steering shaft cause the plug was basically flush with the shaft opening. wound up having to demolish all the original wiring and tap @demogo for help on the plug pinout. albeit, his intelligence had the numbers of the holes on the plugs wrong which was very confusing (I have the corrected numbers off the corner of the plugs) and trying to make sense of the wiring diagram was interesting. the diagram in the manual doesn't have all the wires grouped together at the steering plug, you have to backtrack to where all the switches and lamps are. but even still, the wires were so plastered in electrical tape you couldn't make out what colors they were anyway. so I wound up scrapping everything. I was able to arrive at an acceptable ordering that should be where everything goes originally. see attached my own diagram plug picture and words.

20240312_175334.jpg


the old plug wires
20240311_200435.jpg

photographic evidence of how awful this was
20240312_170135.jpg

don't get me started on the PNL serviced horizontal G07 with the hammered frame to fit.

demogo's intel :) (rotated 90 degrees essentially but a lifesaver for me nonetheless, thank you)

capture-jpg.728178
 
here's another free tip. Spy Hunter at work apparently had a history of the steering wheel going 360 degrees, and with wiring harnesses inside you can only surmise what that does. bunch of wires broke off the female source side plug, but I couldn't even see the wire colors on the male side plug from the steering shaft cause the plug was basically flush with the shaft opening. wound up having to demolish all the original wiring and tap @demogo for help on the plug pinout. albeit, his intelligence had the numbers of the holes on the plugs wrong which was very confusing (I have the corrected numbers off the corner of the plugs) and trying to make sense of the wiring diagram was interesting. the diagram in the manual doesn't have all the wires grouped together at the steering plug, you have to backtrack to where all the switches and lamps are. but even still, the wires were so plastered in electrical tape you couldn't make out what colors they were anyway. so I wound up scrapping everything. I was able to arrive at an acceptable ordering that should be where everything goes originally. see attached my own diagram plug picture and words.

View attachment 735354


the old plug wires
View attachment 735355

photographic evidence of how awful this was
View attachment 735356

don't get me started on the PNL serviced horizontal G07 with the hammered frame to fit.

demogo's intel :) (rotated 90 degrees essentially but a lifesaver for me nonetheless, thank you)

capture-jpg.728178
I think it's just a matter of perspective when I was describing it to you, LOL. I verified everything with my digital multimeter and grounded them all to see the effects, so I knew they were correct.

In hindsight, I should have taken a picture and provided that as well so the orientation would have been clear.

Glad I could help.
 
I think it's just a matter of perspective when I was describing it to you, LOL. I verified everything with my digital multimeter and grounded them all to see the effects, so I knew they were correct.

Glad I could help.
yeah I never know the plug hole numbers either lol I was actually going to use larger molex plugs (which had the numbers) but then was like oh crap, they used these tiny plugs to fit through the shaft. I had smaller molex pins that I got maybe 10 years ago that I never needed until then. the tricky part was I think the holes got enlarged when I removed the old pins, so they don't lock right. either that or my crimpers smashed them the wrong way. I just told Gar it's plugged in, don't ever unplug it again. like we'll have to just set fire to the game if anything goes wrong again later.

also another free tip, the red trigger buttons were mismatched/robbed from different games. I experimented and found that Happ 45 triggers do actually fit and work just right. in case you're in a pinch and need a replacement trigger.
 
Tempest k6100 with a long history of intermittent short axis collapse started doing it again. The last time this happened it was due to a solder joint on a pin of the deflection board P100 frame transistor connector. The "Fonzie test" (light slap on the side of the cab) would restore the picture for a while, as would a very light tap on the connector itself.

Removed all solder from the pins and reflowed. Issue resolved, at least for now…
 
Game PCB: Pengo
Symptom: Game would automatically start on coin up.
Steps: after making a jamma test bench adapter
1) Put game in test and it would flash through first several test screens and stick on control test screen. You could see P1 Start was being registered as permanently on.
2) Ohm'd out p1 start to gnd (@18 ohms) when it should be @ 1k. Looks like input was shorted. Could be resistor pack or IC.
3) Traced p1start to pin 4 of ic22 (74ls253). Clipped pin and short was gone.
Repair:
4) replaced 74ls253 at IC22. No more auto start.

The dip SW coinage is wacky so didn't bother to mess with it but it seems Pengo does not allow more than 2 credits. Just found that noteworthy.
 
This turned into being a tricky one..
Got this one from a friend to get working again. We had discussed the symptoms and in the past, this has been caused by the LS42@H3.

img_5467.jpg
It boots directly to a screen full of dots with two little pink squares in the middle. He replaced the LS42@H3 - but in this case it was not the issue. If you look close it also has two rows of dotted lines at the top.. I've never seen that..

Knowing that this was caused previously from Pin 3 and 4 shorted on the LS42 ..

image.png
I followed the pin 4 output to the LS32@E3.. Pin1 and Pin2 inputs were good.

img_5469.jpg
Pin3 output - not good at all. My friend had checked it with a logic probe.. He really needed to pull out the scope! Game boots now!

However..


This issue I chased for a while. At first it seemed thermal because it would 'ram up' with time. But that was not the case, the colors would change after a time..

I looked at the horizonal output part of the schematic, but it moves ascii characters around and this seemed later in the circuit. One thing I did was just remove the character ROMS@F7, H/J7


Another helpful moment and trick I found was to shut it all off. I pinned the MATCH line to 5v+ and shut off everything(?) in the graphics circuit.

image-1.png

Still getting video noise with everything shut off (I believe). Color mapping could be hiding stuff in theory..

image-2.png
I poked around here for a while and tried to see if I could back trace the noise.. Pinning the MATCH line high did shut off most of the data coming into this circuit. The address bus lines were the only thing really doing anything. One item of note early on - The game had a 6502, not a 6502A. I had put in a 6502A - at the time it didn't make a difference.

image-3.png
I had been back to these two LS244s a number of times. I did Slice and signature analysis on them and they were good. But I happened to piggyback the LS244@B1 and all the noise went away?!

Replaced it and it is still gone. I'd replaced a couple of chips that seemed to be involved only to have them not have any effect. Oddly - I put the original 6502 back in and the trouble returned. So 6502A it is.. Root cause is likely some impedance, noise or timing issue ? Nothing jumped out and I checked each pin. I followed all the lines coming out of @B1 and they seemed ok.

Adding to the complexity - the PCB does not completely match the schematics. I looked for a different revision, but could not find one. Learned more about Centipede for sure..

img_5494.jpg
I gave it a good workout, Board works!
 
I have definitely had some weird stuff like that before. Thanks for sharing the detail.

I did fix my defender last night. Easy peasy ram37 error...swapped in new one and all good.
 
***** Some late breaking news on the Centipede repair I just posted ****
After reading the post, my buddy sent me this pic from the LS42 he replaced..

IMG_1293.jpg

It originally had this cap attached, but it didn't make it to the replacement LS42. I popped the original 6502 back onto the board and the noise returned, nice!

IMG_5501.JPG

Went into my stack of Centipede boards and found one with the same (factory) modification.
Pin 6 to Pin 8 - part of the COLORAM signal - which is where I had spent some time AND where this version of the PCB doesn't match any of the schematics that I could find.

Moved this cap over to the board under repair: Noise problem resolved again!! But this time with the 6502 (not the 6502A) in place. The donor board had a 6502 on it.. Clearly a very early revision of the PCB.

Still, I learned a bunch about the board and I have a better idea what to look for in the electrical noise department - Next time - I'll just pop a cap in it.
I also like that the issue makes MUCH more sense now.
 
Last edited:
I had a goofball one last night. I accidentally found the issue with a donkey kong board on my bench. I was poking around the moving objects circuit because I had a "dead zone" where moving objects would disappear.
PXL_20240513_120143741~2.jpg

So while poking around I set my hand on the board near the LS161 at 5L. I just so happened to touch the via of the output of 5P which unknown to me at the time was floating. My hand had effected the signal just enough to register as a "valid" signal. After replacing the LS30 at 5P, it fixed my issue. Looking at it on my chip tester, it confirmed my findings.
PXL_20240513_011321692.jpg
For giggles I also did a youtube video showing this. It's really funny to me how these things work out sometimes.
 
Back
Top Bottom