Centipede PCB high pitched "Hum" & static on screen...

keithsarcade

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Centipede PCB high pitched "Hum" & static on screen...

Got a new PCB for my Centipede, it is making a high pitched noise, almost like a monitor hum, but the noise is coming from the PCB itself. I am also noticing static on the screen in the background, but only when my brightness is turned up. PCB is working flawlessly otherwise. My ARII is fine as is my monitor, I have not tried reading voltages on the PCB yet. I have tried reseating chips and cleaning the edge connector with no difference.

Anyone familiar with this? Is this something that could present a bigger problem later? What should I do?

I can make a short YouTube video on this if it would help also.

Thanks in advance.
 
Got a new PCB for my Centipede, it is making a high pitched noise, almost like a monitor hum, but the noise is coming from the PCB itself. I am also noticing static on the screen in the background, but only when my brightness is turned up. PCB is working flawlessly otherwise. My ARII is fine as is my monitor, I have not tried reading voltages on the PCB yet. I have tried reseating chips and cleaning the edge connector with no difference.

Anyone familiar with this? Is this something that could present a bigger problem later? What should I do?

I can make a short YouTube video on this if it would help also.

Thanks in advance.

Yes could you make a video? I can't think of anything on the *board* that would make a sound like that.
 
Do you remember what the fix was? Or more importantly which component was making the noise?
 
Make sure the "slam" switch on the coin door is not stuck shut. At least two of us here have had this same problem and the cause was a stuck/jammed/shorted slam switch.
 
AR

Do you remember what the fix was? Or more importantly which component was making the noise?

It happend to me last week when I was testing 10 or so AR boards. I marked it as works with static. I have not atempted to repair it yet since I have so many working ones. I plan on getting to it as soon as my pile of ARs gets low.

Oh teah. The static was from the speaker not the board. I cannot think if anything on the board its self that would make a noise other than a sizzle.
 
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Yes could you make a video? I can't think of anything on the *board* that would make a sound like that.

http://www.youtube.com/watch?v=dox1yT3gphU

I am using the same ARII that I previously inquired about in this thread:

http://forums.arcade-museum.com/showthread.php?t=120241

Voltages are the same, and similar voltages come up on the PCB so everything seems normal. I used the same ARII with my old PCB which wasnt saving high scores, but didnt have the static or hum. This PCB is saving high scores and plays fine, just has that static (only with brightness turned up slightly high) and hum from the PCB.

I am not too worried about the issues themselves, but want to know if this could be a sign of things to come.

Make sure the "slam" switch on the coin door is not stuck shut. At least two of us here have had this same problem and the cause was a stuck/jammed/shorted slam switch.

Slam switch is ok, only buzzes if I push the contacts together.
 
Yep, it definitely didnt do that when I shipped it out to you. Is it possible that the video connection came a tad loose as you were undoing the harness?
 
It sure looks like either grounding or AC noise issue to me. Are you sure the noise isn't coming from the speaker? Try running the game:

* with the speaker unplugged.

* with the monitor unplugged.

* with both the monitor and speaker unplugged.

See what you get. Are you running the monitor with an isolation transformer? Check to make sure the grounds from the monitor, AR-II, cpu board, and the ground pin on the outlet plug are all good. IIRC they all star back to the frame on the power brick.
 
Hum

It sure looks like either grounding or AC noise issue to me. Are you sure the noise isn't coming from the speaker? Try running the game:

* with the speaker unplugged.

* with the monitor unplugged.

* with both the monitor and speaker unplugged.

See what you get. Are you running the monitor with an isolation transformer? Check to make sure the grounds from the monitor, AR-II, cpu board, and the ground pin on the outlet plug are all good. IIRC they all star back to the frame on the power brick.

I was assuming on mine that it would be a bad filter cap on the ar causing ripples.
 
Ok, it just dawned on me what you really meant by "but the noise is coming from the PCB itself". Not the case where something on the pcb is physically vibrating and causing sound, but something electronic bleeding into the audio and/or the monitor. Jeez.

You have an AC ripple somewhere, either on one of the voltages going to or coming from the AR-II, or on the ground. With the pcb plugged in, the LM324 amps would amplify the AC ripple and you would hear it out the speaker.

Try swapping out the AR-II with another AR-II -02 or -03 and see what happens. Also try another brick if you have one. It could be a bad filter cap either on the AR-II or Big Blue. Well it could be anything that would cause voltage ripple.

Still, try the suggestions in my previous post as well.
 
It is definitely not coming from the monitor or speaker. I have unplugged the monitor and it makes the same noise. I havent unplugged the speaker but I can tell thats not the problem, like I said, you dont really hear it when the game is sealed up, you can put your ear to the speaker and its silent. I suppose the noise could be in the ARII, but this didnt arise until the PCB was replaced.

I will look for a loose ground but everything else seems fine. Already looked at the connectors and reseated chips. Big Blue is original and so is the ARII (and I dont have another ARII to try, plus I already sold and shipped the original PCB), power brick is also original, with original xformer.

Can I rule out the PCB causing the problem? Is it definitely either in the ARII and/or big blue?
 
Ok so I was right the first time - you're thinking that the physical source of the noise is coming from either the main board or elsewhere? There's nothing on the main board or AR-II that would be giving off sound waves. Could it be coming from the transformer on the power brick? If the transformer core is loose it could be vibrating and making noise. It is all inside a closed box, maybe echoing around.
 
Everything is nice and tight including the xformer. Just popped it open again today and put my ear to things as "safely" as I could without shocking myself. I'm still going with the PCB, its loudest there, and its the only thing I replaced. I will eventually put a new big blue in and see if it helps any. I also tried removing lamps at the coin door and marquee (interference?), no difference.

Any more ideas? Or can anyone at least tell me if I should even be concerned?
 
It's reading -50 ohms.


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