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(Topic ID: 272823)

Flash audio hum


By DennisT

4 months ago



Topic Stats

  • 13 posts
  • 6 Pinsiders participating
  • Latest reply 3 months ago by DennisT
  • Topic is favorited by 2 Pinsiders

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#1 4 months ago

I hope this is a simple fix. My Flash has always had what could be described as a loud ac hum at idle. The board is a type 1 version 2 and has been recapped. There’s no hum when connected to dc power on the bench. I also have another board I tried that also has the same humming issue.

I searched the forum and didn’t see anything about this problem.

Anyone else ever have this problem?

Thanks

Dennis

#2 4 months ago
Quoted from DennisT:

I hope this is a simple fix. My Flash has always had what could be described as a loud ac hum at idle. The board is a type 1 version 2 and has been recapped. There’s no hum when connected to dc power on the bench. I also have another board I tried that also has the same humming issue.
I searched the forum and didn’t see anything about this problem.
Anyone else ever have this problem?
Thanks
Dennis

These boards will have some hum but it should be inaudible unless you get your ear up to the speaker or turn the volume way up. If two borads have identical type hum its probably not the sound board.

I had a time warp where the power board square 6 pin (only 2 wires used), where ground comes in, burn up and cause the nasty hum out of the sound board. Even tho the sound board has its own transformer tap and power supply, a ground problem on the main power supply must be able get noise into the sound board. Try reseating that plug with the power off and see if the hum changes.

Check the flash manual page 21 and 22, these pages are reversed in the IPDB scan pdf file. It should not apply to a type 2 sound board but they have some notes about noise you may want to read.

#3 4 months ago

Thanks for the info. The game has a very loud hum that only goes away if the sound board power is removed. Interestingly enough the hum remained even after removing all power to the ps board. The only thing left in the circuit that I suspect is the input line filter. I’ll remove it and see if the hum remains or not. Funny thing though, while I was looking around on line for a possible replacement one website even mentioned that a loud hum is a sign of one gone bad. I’ll report back tomorrow.

#4 4 months ago

there are two causes- ac on the dc line which you can check with a dmm and bad caps which is pretty much the same thing- 1- make sure your game has a 3 prong plug that is wired right- make sure the gnd straps are all connected- unplug volume knob as they go bad and cause this- most likely- recap your boards- ac hum comes from bad caps= not just sound board but all boards need new caps

#5 4 months ago

hum is ac over dc

#6 4 months ago

Here’s an update. First, both boards have been recapped (electrolytics). Just for the heck of it I replaced the tda2002, no change. The last thing I just tried was to see if it would hum in another game. So I installed it in my Contact pin and it is as loud as when it’s in Flash. Now here’s the weird part. Contact has the older type 1 version 1 board in it. When powered up it has the same loud hum but only for less than a second then it goes away, like a cap charging. I think the next to try might be pulling the caps and checking them to make sure they are what their supposed to be.

3 weeks later
#7 3 months ago
Quoted from DennisT:

Here’s an update. First, both boards have been recapped (electrolytics). Just for the heck of it I replaced the tda2002, no change. The last thing I just tried was to see if it would hum in another game. So I installed it in my Contact pin and it is as loud as when it’s in Flash. Now here’s the weird part. Contact has the older type 1 version 1 board in it. When powered up it has the same loud hum but only for less than a second then it goes away, like a cap charging. I think the next to try might be pulling the caps and checking them to make sure they are what their supposed to be.

Any updates? I just acquired a Flash machine and I have what I think is the same hum. If I power up the game and it’s in attract mode it’s pretty darn loud.

I’m sending all my boards out for a refresh and we’ll see it that happens to help or not.

#8 3 months ago

Watch this video, it worked on my Time Warp.
-Mike

#9 3 months ago
Quoted from Grizlyrig:

Watch this video, it worked on my Time Warp.
-Mike

Sweet, going to give this a try soon. Thanks!!!

#10 3 months ago
Quoted from Grizlyrig:

Watch this video, it worked on my Time Warp.

Thanks for sharing. I have never come across this particular solution. It doesn’t completely eliminate the hum for me, but it definitely makes a HUGE difference!

#11 3 months ago
Quoted from Timmo:

Thanks for sharing. I have never come across this particular solution. It doesn’t completely eliminate the hum for me, but it definitely makes a HUGE difference!

I agree it wasn't a 100% fix, maybe 75-80% difference for me. The install of a new cap kit also helped,sound board was all original.
-Mike

#12 3 months ago

So the guy removes the center tap ground connector pin from the transformer power input it reduces the hum. Wouldn't that just mean he has a ground potential issue at the place where grounds actually come together? That hum is not norrmal on sys3-6 games. Sys 11, yes to some extent.

I have had that hum in system 6 game firepower(similar sound) and I want to say the 6pin square shaped ground plug on the power board was the caused. Can't remember exactly but pretty sure fiddling with that plug made the hum go in and out. Repin it made the hum go away.

2 weeks later
#13 3 months ago

Hey guys, great discussion. I haven’t given up on this problem and I’m going to find it if it kills me. As i said before, my Contact pin which has the version 1 board in it is completely free of hum. So for the heck of it I picked up a version 1 parts board off of eBay and recapped and replaced the missing volume control pot. I wanted to see if the lack off hum was a fluke or not. Powered it up on the bench and it works perfectly, no hum like the other. So my next step was to read the ac across all the caps. As it turns out both the ver.1 & 2 boards have about the same readings. The caps on both boards are new and the same manufacturer so I don’t think their the issue. So for now I have a couple of things I want to try so I’ll report back in a day or two. I’m not giving up.

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