Fixing A 1980 Atari Centipede PCB Another Tech GAVE UP ON! Classic Arcade Game Board Repair 

Recognizing the symptoms of something not working is way more valuable than completely understanding how it works.

Imagine the syncing feeling the other tech had when he couldn't fix it. An oscilloscope would be nice to have to look at those little square horizontal waves and see what's really going on in there.

Nice fix! If I understand the counter right, it is a binary divider. Technically the "2" output would change state every time the chip receives a strobe pulse, the "4" output would change state every time the "2" output cycles once, and so on, so every output would pulse at half the frequency of the previous. The probe even produces a "beat" tone that somewhat correlates to the frequency of the pulsing in a certain range. The composite output woud have some of the H sync pulses masked out by the V signal and the AND gate, so every time a few consecutive H pulses are missed the monitor would restart drawing from the top. Now that there is no gap in the H signal the monitor will just constantly draw the stuff that comes out of the color lines. Also it will draw transitions in video RAM content, as normally the V blanking would turn drawing off while the video memory is edited. So it makes full sense to use the same counter signals to access the video RAM during the V blanking. Otherwise you would occasionally see part of a character in its old location and the rest in the new location.

My friend Donna Bailey coded Centipede. She is an amazing person!

You don't just fix stuff, you FIX STUFF.

Very cool. They used to make kits (pins & removal/installation tool) to replace those AMP pins. Now, finding one of those kits from the 80s is the challenge!! (BTW, very nice job fixing that connector!!)

My wife loves Centipede. Whenever we get to an arcade that has one she has to play. Then when she’s done I’ll always play and beat her high score BUT I never tell her. Happy Marriage. Silent satisfaction.

This was a really interesting fix. You guys proved you don't need much basic electronics knowledge to fix basic electronics. Just enough to get by is all you need. The descriptions of what was going on in the circuit were almost complete nonsense, but you fixed it and that's all that matters. Top marks for enthusiasm.

Love these videos, I’m picking up a centipede next week which hasn’t been powered on for 30 years so I’ve started doing my homework in case something is funky when I get it home. Thanks for documenting this process!

I have MISSED these arcade repair videos!

You probably already know this but those AMP connectors and pins at 2:38 appear to have availability at Digikey. Look for 583859-3 and look to the bottom of the page for associated products. Thanks for the continued content...

Sure you could hear the difference on the probe. I was screaming at you that the lines were stuck 😂

great video. for those wondering, the line over the words on the schematic means: "active low". which is just basically inverted output, when its "on" its 0V and "off" is whatever the high voltage is. "not" is a great way of explaining though.

seems to me that a few repairers have tried to fix this old girl, to my shame I bought a broken one but never got around to fix her and was a coffee table for a few years before I sold it. Well worked out another one repaired and given a new life by the pair of you.

You say you never went to school, but you're pretty good at this....

You can go so far with experience but a good schematic is a godsend when troubleshooting. Nice work Ron! Especially since you always put yourself down as a not educated repair man. =) I would hire you just because you have the thinking faculties/knack for it compared to many people I have met that ARE educated with some piece of paper to prove it. And, yeah, they were not up to the task, paper and all. Thumbs up as always.

i don't know if you are aware, but if you pause the YT video at 10:00 is like you say, the 3 images you speak are there still and very clear.

Just wanted to say great job on the F14 TOMCAT. Looked a lot better than I imagined.

When I saw the picture it reminded me of a Quadrapong I did once (which had only 120 games on it and of course no CRT burn). Here the video address generator was broken in a non-noisy way so I could get the picture to sync up to four playfields horizontally and two vertically (or something). I couldn't find schematics for it so I went looking for counter ICs and... just piggybacked them. Turned out, they used 7493 in the middle of the board and one of them gave me one playfield when piggybacked, so there you go. And then we spent the rest of the evening playing Quadrapong. Awesome game, a lot more fun than a the player PONG table we had! Also iirc the first game where you had "lives".

I use the b/w output to display an image on my pvm with my test bench. You can also just cut an rca cable and plug it into an old tv. There's two test points to attach gnd and video. It's nice because you can see if it boots with just 5v and a tv.

This logic probe looks quite useful. It could be improved quite some ways: - the tip (just a screw?) looks nasty nasty. I like fine sharp tips much more. Especially if they are easily replaceable. - while 2 LEDs for low and high signal and tone generator are fine and cheap, I would suggest stepping it up a little. There are small/mini OLED diplays and quite fast microcontrollers with built-in ADC-s and they cost maybe 10-20$ max. So you could build a little oscilloscope right into the probe! It does not need to show exact voltage or frequency or support extreme voltage ranges, just a approximate waveform would do.

good morningJjoe. you sure have saved a lot of old Atari's. Great job.

You say you are no "technical guy" but I think you are doing it great, greetings from a professional electronic repairer ;)

Nice work, I love this game, one day I'm gonna get one, after I get a Defender !.....cheers.

Hey I just noticed that if you pause the video... the monitor looks correct.... you can see the high scores and the mushrooms etc.... (maybe you can use that as a troubleshooting technique in the future)

How exciting... haven't seen an Arcade PCB repair for a bit... yay!

Hi Ron, great videos! With that faulty counter the frequency/tone was increasing with each pin whereas the good one was decreasing 😀

Just Pleasant and awesome at the same time !!!!!!!

I’m glad your thumbnail got Filter stuck in my head lol

Pin 15 on N2 is the one that feeds the next counter. The other lines feed the address to the ram so the right data goes out to the monitor. Probably the output on pin 15 or one or more of the input pins on N2 went bad. They definitely sounded different after the repair. Hope to see it fully restored. The wave should be square not smooth...

Smooth and swimming. Thanks for sharing the process. Great video was always.

Great repair, I stopped taking on "had a go" pcbs due to various reasons. A couple ive had in the past were that messed up, work done and parts replaced for no reason only to find the issue was a socket issue.

Thanks for the vid, if I remember rightly when the line is above something it’s active low and when the line is at the bottom it’s active high 😏

Ahh, the NOTORIOUS jumbo capacitor on the Atari power supply! Always made me laugh how Atari literally filters the output of the bridge rectifier with a SINGLE CAP!

I love PCB repair videos!

The master at work.

As long as you say "MicroFarad' everybody is happy! 😉👌 Nah, just kidding! Say whatever you like! Cracked up a can of beer and enjoying the ride! Keep up the good work! Cheers! Oh yeah, Hello from Finland, the city of Turku!

I flipped centipede for the atari 2600 as a kid, it flips through all the colors and looks like the beginning but you are still playing and have control. I remember thinking it reset but noticed that the controls still worked.

I have a box full of "bad" counter chips. Most of them are not bad, but had a bad solder joint. But you may as well replace it if you have to get out the iron.

Is that a screw you are using as the probe tip on your logic probe, or is that tip threaded to screw a slimmer tip on it? Was thinking it might have been a field repair for a broken tip….. By the way, if you are self taught in this stuff, you surly have done a good job in how you learned it, I do love watching the nice, logical, step by step approach you use in your troubleshooting!🙂📟🕹

Nice to see an arcade repair. Thanks!!

I love your channel. Thank you for the great videos!

FYI Line over a label means "inverted" as in the opposite state.

Love to build my own arcade machine one day..hope y'all are staying cool during the heatwave you guys are having up there🔥

Nice song reference for the title. Trying to sneak one by me.

We live in a backward world, Ron. I'm a proud southpaw as well.

13:24 I'm an engineer and I love these videos lol

This is such a great video! Thanks! When you think about audible frequencies, you'd expect the lower frequency to have a lower pitch. When you first tested the old counter, the pitch was actually going up with lower frequency pins, and after you replaced it the pitch went down as it should be. By the way, does AMP stand for Amphenol? They were very big in the telecom market, maybe there's a source for new pins/parts in that part of the universe.

Can't beat a Big Black Capacitor.

Easy to tell if it’s a monitor problem by scoping the composite sync and checking for 15,360 Hz. If you have good sync then the video should be locked in clean, whatever the image happens to be. SKIP those unreliable edge card connectors and hard solder wires directly to the fingers of the PCB and switch the connector to an off-board MINIFIT JR type connector

The line over it (or a / before it) means the signal is inverted, so active low. On binary counters, that is one way to divide frequencies. So the CPU clock is likely sent to the counters, and the correct frequencies are tapped off. A counter count once per high/low transition, so the lowest bit would be half what goes in, and the next one is half of that, etc. Now, the reason both directions were screwed up is that the vertical is derived from the horizontal. Notice the line going to the other counter pair. That is the carry out on one chip and carry in on the other. So the other bank divides the 15,750 Hz or 31,500 Hz (whatever the horizontal is which could be between the 2 numbers I gave, like around 22-24 Khz) down into the 60 hz. So if the higher frequency counter is messed up, all the other counters past that will also be messed up since they chain the carry signals. Having one bit messed up would cascade to all chips that are connected through the carry in and out lines.

Another awesome video!

Leetle Son of Beach chip! ;)

Right on man, keep them arcade repairs/restores coming! One of my fav. channels, great vid...thanks. Man that's weird that amp connector/pins was on there.....All my Atari Games had the 44 pin molex stock(like the smaller pcb connector there), that can't be original.

When you pause the video, you can see the 3 redraws of the same thing. maybe should try that some time to get another look at it. does not fix it.. but may give you more info

Most modern-ish multimeters now have a Hz setting.... you can use that on the H and Vs and check frequencies... hoping for 15kHz at H256 and 60Hz at V256... or something like that... doubling as you go down. Just sayin'.... did I just say... "I wouldn't have done it like that"? No I didn't. Good job!

Favorite game

The mpu board looks like a mpu board from a pinball machine except a lot bigger, is it? Is the power supply the same way? Great video Ronnie, Gorgar is still talking.

i think there's a version of centipede on my old nokia phone. i know what you mean, good schematic makes allllllllllllllllllllllllllllllllllllll the difference

N2 was reversed based on the sound of the pulses.

Damn your shop is a pig sty. Love the content.

Ron , I am wearing my Play at Joes T Shirt and I was wondering do you actually have an Arcade where you can actually play games or do you just sell and repair Machines and Games ?

Ever tried Mouser and Digi-Key for parts?

Hi Ron! Point of curiosity; When troubleshooting a board set, like this one, and you run across a suspect, non-socketed chip for which you have a replacement in stock, and on hand, as a matter of course, do you simply socket the board, and replace the chip, or do you first piggyback the known good chip onto the suspect chip, to see if that corrects the problem? I've seen both approaches, and both are certainly valid, but I was wondering if you had a preference.

If there was no hsync coming out of the d latchs why would you change the second counter if the first counter feeds the d latch?

Nice. Have you got one of those usb scopes, I ask because it looks like you preferred to replace a few chips rather than look at the output signals? I don't know how good or fast they are, just asking as you have lots of experience.

you have to buy bigfurcated to get the big bifurcated

Watching

31:45 I'm not convinced that you really understand how that circuit works. That's a digital circuit (at least the part you're looking at in the schematic), so there's no analog wave that's happening there. Everything happening at that stage is happening (or supposed to be happening) in a square wave, not a "swimming" sine wave.

Cool fix. Why is the language in Spanish? Can that be changed to English???? COME ON PEOPLE!!!!!!!! ;)

Throw the logic probe away and get yourself an oscilloscope

Don't trust prior work. Sorry - not sorry.

Hay Ron help meeeee!!! Lol Iv emailed you