G05-801 top half of screen vibrating

Kadajett

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Hi all! I am new to Klov, and arcade tech altogether, so please forgive any inconsistencies :D
I have an original asteroids cab that is mostly functional, but the top half of the screen will wobble and then collapse at random. It's jiggling while the game is on, and occasionally going back to normal for a few seconds, but then back to laser disco.
I have done quite a bit to this machine so far, so maybe something here will help to suss out the next steps.
  1. The customer gave it to me playing blind with the spot killer on. Reported loud buzzing.
  2. There was a scorched ground pin on the main board's Jamma connection top when I opened it up (Repaired with some copper tape and circuit board epoxy, since it was really toasted)
  3. F700 on the monitor was blown. Replaced when replacing bottlecaps.
  4. Tests failed on 2N3792, so I just replaced all the bottlecaps on the monitor chassis(2*2N3792, 2*2N3716)
  5. After this, we have no spot killer, and the screen is having a fiesta on the top 30%-50%, but working otherwise.
  6. Recapped the main circuit board.
  7. Confirmed x/y offset
  8. Confirmed brightness and contrast weren't out of whack (lowered brightness until just barely visible, then increased contrast)
  9. stared at it really hard
I have ordered a monitor cap kit and will report back if that helps. But, I am curious if any of you have seen this before and can pinpoint the issue directly! This is the first electronics repair on an arcade machine. I am a software guy by day, so this is a huge learning experience for me so far. And I haven't been shocked yet, thankfully 🙏

Below is a video of it running now with the current issue. Any help would be greatly appreciated!

 
Since the problem is intermittent, I'd go back and confirm continuity on Q608 and Q609 Q607, reflow the solder joints at the socket and deflection PCB.
 
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Since the problem is intermittent, I'd go back and confirm continuity on Q608 and Q609, reflow the solder joints at the socket and deflection PCB.
Will do! And when I said intermittent, it's probably 95% collapsed, and 5% fixed. But, your comment is a good bet. Just gotta find Q608/9, since I don't see a result in my search on the G05-801 monitor manual 😁 I will report back asap! Thank you!
 
Will do! And when I said intermittent, it's probably 95% collapsed, and 5% fixed. But, your comment is a good bet. Just gotta find Q608/9, since I don't see a result in my search on the G05-801 monitor manual 😁 I will report back asap! Thank you!

They're the big bottle cap transistors mounted to the side of the frame. There's four of em, two for the y axis and two for the x axis. Since you're only getting collapse on one half to the center of the screen on the Y-axis, it's likely one of them has an intermittent connection. Also it's Q607&608, went the wrong way with one of em, lol.

1743450909326.png

  1. There was a scorched ground pin on the main board's Jamma connection top when I opened it up (Repaired with some copper tape and circuit board epoxy, since it was really toasted)
Also just noticed this, but JAMMA is only one specific type of arcade edge connector pinout, Asteroids predates JAMMA by quite a bit.
 
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" Asteroids predates JAMMA by quite a bit." Derp. You are right lol

And I see! Yeah, I replaced those in my original round of fixes, but I will go and reflow the joints on it and see if that helps! Thanks again!
 
That's an issue where it's possible it could be the game board. So before you chase things too far, you really want to use a scope to make sure it's actually the monitor. (Or swap another known-good game board in there.)

Also FYI, cap kits on Atari game boards are not necessary. The caps on those are still fine. Capping a game board won't fix a problem. You do want to cap the monitors however, as those caps run at higher voltages and temperatures, which are two factors that cause caps to age faster.

Have you reflowed the solder joints on all of the deflection board headers?

Also, look into all of the deflection board header connectors, and make sure none of the contacts inside the connector housing are bent. They should all line up with each other. If any are pushed in further than the others, they may not be making reliable contact with the header pin.
 
That's an issue where it's possible it could be the game board. So before you chase things too far, you really want to use a scope to make sure it's actually the monitor. (Or swap another known-good game board in there.)

Also FYI, cap kits on Atari game boards are not necessary. The caps on those are still fine. Capping a game board won't fix a problem. You do want to cap the monitors however, as those caps run at higher voltages and temperatures, which are two factors that cause caps to age faster.

Have you reflowed the solder joints on all of the deflection board headers?

Also, look into all of the deflection board header connectors, and make sure none of the contacts inside the connector housing are bent. They should all line up with each other. If any are pushed in further than the others, they may not be making reliable contact with the header pin.
I did measure the caps on the main board, and a couple were way out of what I would expect, funny enough! I ended up replacing them all since they had seen better days.

Is it a problem if the ones on the main board are more than 20% over the capacitance expectation?

And I will have to bring the cabinet home to test on my big O-scope. I doubt my little mobile automotive one can show x/y like that, but it would be cool as heck to try!

And nope, I haven't reflowed anything on the deflection board yet! I will ASAP!
 
I did measure the caps on the main board, and a couple were way out of what I would expect, funny enough! I ended up replacing them all since they had seen better days.

Is it a problem if the ones on the main board are more than 20% over the capacitance expectation?

And I will have to bring the cabinet home to test on my big O-scope. I doubt my little mobile automotive one can show x/y like that, but it would be cool as heck to try!

And nope, I haven't reflowed anything on the deflection board yet! I will ASAP!


For the caps, what did you measure, and how were you measuring them?

And yes, reflowing the headers on the deflection board is the first thing to do with any vector game. They are almost all cracked if original.
 
For the caps, what did you measure, and how were you measuring them?

And yes, reflowing the headers on the deflection board is the first thing to do with any vector game. They are almost all cracked if original.
I desoldered and pulled out and measured with my capmeter out of circuit, just in case.

C25, C70, C90, C92, C93
C117
C19
C86,C87

C90 and C93 came in at 1.6UF instead of 1UF
C86 came in at ~370UF, instead of 470UF.


If that's all fine, then hopefully I just gave them another 40 years of running :)
 
I desoldered and pulled out and measured with my capmeter out of circuit, just in case.

C25, C70, C90, C92, C93
C117
C19
C86,C87

C90 and C93 came in at 1.6UF instead of 1UF
C86 came in at ~370UF, instead of 470UF.


If that's all fine, then hopefully I just gave them another 40 years of running :)


Many of the electrolytic caps on these boards are used for power rail filtering. As a result, many of them are redundant. You could physically cut them off and the board would still work. So a lot of the caps aren't even critical.

Also, the tolerance of the capacitance value on many caps was never precise from the factory. +/-20% is a base for electrolytics. But they can be even further out than that and in most cases things will still work.

The critical parameter for electrolytics is not capacitance, but rather Equivalent Series Resistance (ESR). Capacitance measures how much charge a cap can store. ESR measures how fast or slow that cap can take in or let out that charge, which is the main thing a cap needs to do. When electrolytic caps do go bad (in ways that will actually affect operation), it's almost always because the ESR goes too high.

The problem is, most DMM's don't measure ESR. A separate ESR meter is required for that. There are threads here about them, but they are a good thing to have, as they will tell you exactly how healthy a cap is, and you can measure them in-circuit, without needing to remove them. Here are several threads about ESR meters, if you want to know more:



Of the two parameters, ESR is actually the important one to measure. Because it's very possible to have caps whose capacitance is spot on, but the ESR can be high. And practically speaking, that will be more likely to cause problems than a cap whose capacitance is way off, but the ESR is ok.

Note that these are general rules of thumb. But I've repaired thousands of Atari game boards, and speaking to those specifically, I have never seen a problem caused by a bad electrolytic cap. Unless they are physically damaged or corroded/leaking, the originals are fine. (And even then, I've seen plenty of dented and damaged caps that still actually test ok for ESR and capacitance. Those I will replace. But I even saved a bunch of them, and populated two AR's with only dented caps, which are running to this day in my Pole Position. Just as a test, to show it's possible.)

Some people go out when they get a new game and buy every replacement part that someone will sell them, thinking they are 'upgrading' things. And that's a mistake. There are people out there who are perfectly happy to sell you parts you don't need, simply because they know people don't know any better, and they make money from it. But the more you learn about what really makes these games fail, the more you realize how much time and money people spend replacing things that aren't necessary.

I take the opposite approach, and generally only replace what actually tests bad, and will make the game not work, or make it less reliable. I treat these boards more like vintage cars or furniture, where you want to preserve as much as possible of what's there, only replace what's needed, and if there's anything you can keep original, keep it original. You're also preserving the value and history of the board.

Any time you touch an iron to a board, you also run the risk of unknowingly causing new problems and not realizing it. So you really only want to replace parts when you know it's absolutely necessary. And there are plenty of instances where that's the case. But caps on Atari game boards and AR's are not one of them. Better to save that money and spend it on other parts.
 
Many of the electrolytic caps on these boards are used for power rail filtering. As a result, many of them are redundant. You could physically cut them off and the board would still work. So a lot of the caps aren't even critical.

Also, the tolerance of the capacitance value on many caps was never precise from the factory. +/-20% is a base for electrolytics. But they can be even further out than that and in most cases things will still work.

The critical parameter for electrolytics is not capacitance, but rather Equivalent Series Resistance (ESR). Capacitance measures how much charge a cap can store. ESR measures how fast or slow that cap can take in or let out that charge, which is the main thing a cap needs to do. When electrolytic caps do go bad (in ways that will actually affect operation), it's almost always because the ESR goes too high.

The problem is, most DMM's don't measure ESR. A separate ESR meter is required for that. There are threads here about them, but they are a good thing to have, as they will tell you exactly how healthy a cap is, and you can measure them in-circuit, without needing to remove them. Here are several threads about ESR meters, if you want to know more:



Of the two parameters, ESR is actually the important one to measure. Because it's very possible to have caps whose capacitance is spot on, but the ESR can be high. And practically speaking, that will be more likely to cause problems than a cap whose capacitance is way off, but the ESR is ok.

Note that these are general rules of thumb. But I've repaired thousands of Atari game boards, and speaking to those specifically, I have never seen a problem caused by a bad electrolytic cap. Unless they are physically damaged or corroded/leaking, the originals are fine. (And even then, I've seen plenty of dented and damaged caps that still actually test ok for ESR and capacitance. Those I will replace. But I even saved a bunch of them, and populated two AR's with only dented caps, which are running to this day in my Pole Position. Just as a test, to show it's possible.)

Some people go out when they get a new game and buy every replacement part that someone will sell them, thinking they are 'upgrading' things. And that's a mistake. There are people out there who are perfectly happy to sell you parts you don't need, simply because they know people don't know any better, and they make money from it. But the more you learn about what really makes these games fail, the more you realize how much time and money people spend replacing things that aren't necessary.

I take the opposite approach, and generally only replace what actually tests bad, and will make the game not work, or make it less reliable. I treat these boards more like vintage cars or furniture, where you want to preserve as much as possible of what's there, only replace what's needed, and if there's anything you can keep original, keep it original. You're also preserving the value and history of the board.

Any time you touch an iron to a board, you also run the risk of unknowingly causing new problems and not realizing it. So you really only want to replace parts when you know it's absolutely necessary. And there are plenty of instances where that's the case. But caps on Atari game boards and AR's are not one of them. Better to save that money and spend it on other parts.
Holy crap, what a great write-up! I will keep that in mind as I go on to fix the next few games!

I was initially at a loss and saw the cap kit on arcadepartsandrepair, so I thought "Why not?" I will certainly save the cash next time unless I see a sign pointing to them as the issue.

I have only been waist deep in 2 cabinets so far, and I already wish people had the same mindset as you. Some real jerry-rigged stuff out there :bigeyes:
 
Glad you appreciate the 'less is more' approach. Many people don't. (And yes, there's a lot of hacked up stuff out there.) :)

For anything you need to fix, the best advice you can get is to search for past discussions here first. You're better off spending an hour searching and reading, than spending that same hour replacing parts and guessing. As you'll see me say in a lot of threads here, guessing is not a valid troubleshooting strategy.

The archives here contain over 20 years of discussions contained in over 500,000 threads, which cover pretty much every issue with every game you could ever run across in this hobby, with many solutions discussed. The more you read, the more you'll learn what really need to be done, versus what doesn't.

Also, the advice I gave above for game boards really mainly applies to Atari boards. But the key is to look at the brands of caps any board uses. Atari used top-shelf brands like Nichicon and Elna, and you see the difference after 40 years. Other game companies used mid- or low-tier caps, and those you can see bad on game boards sometimes.

This is really where it pays to invest the $100 in an ESR meter, so you don't have to guess. When you use it enough, you'll eventually learn what brands of caps tend to go bad more than others. If you plan to be in this hobby a while, an ESR meter will easily pay for itself in the caps you won't need to buy, and the time you don't need to spend replacing them.
 
Reflowed everything that needed it and it was even worse. I gave it one more try and... Molex connector was messed up. We are 100% working now thanks to yall!

I really appreciate all the help! Learning a ton already. Next, I have a broken missile command to fix!
 
Nice work.

Which connector, and what was messed up about it
8-pin(I think. I was moving quick) wiring harness from the edge connector to the monitor had pin 2,2 not fully locked in.

Right now, it runs like a dream and looks absolutely amazing. Also, I do see the bottlecaps getting very hot on my thermal cam. Not sure if it's normal yet.
 
It's normal for them to get pretty warm. That's why they're mounted on that huge heatsink.

Does the thermal cam tell you the temperature? They should be toasty, but not scorching hot (i.e., too hot to touch).
 
I didn't capture the temperature before I went home, but touching the second one from the rear spooked me with how hot it was. It's not fire hot, but I don't think it's long for this world.

The arcade is all shut down for tonight, but I will drive over there tomorrow and check the temp before it sits open for too long.
 
"Nice work." Also, thanks <3 Bar owner hasn't seen the message yet, I don't think. But this was his first ever machine, and I am sure he will appreciate it being alive again.
 
If any one transistor is hot, it's less likely an issue with the transistor, and more likely a symptom of something else being wrong on the deflection board.

One thing you should do is test the outputs of the power supply board in the monitor.

All you have to do is unplug the output connector on the right side of the power board. (The one on the bottom of the monitor, with the two huge caps on it.) There's a 6-pin connector (2x3) on the left side of it, that's the input. The other one on the right side is the output.

Keep the input connected, but remove the output connector, power the cab up, and test the voltages on the pins of the output. The voltages for each pin are printed on the silkscreen. Pins 1 and 2 should be +25V DC, pins 3 and 4 are ground, and pin 5 should be -25V DC. Pins 7+8 are 6.3V AC. But you want to make sure the +25 and -25 are correct. (Also, ignore the +/-35V on the diagram below, those pins should be +/-25V.)

Be careful not to short your DMM leads between the pins.

1743571482280.png
 
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