(Topic ID: 24704)

Data East speaker noise - ideas for a cure


By roc-noc

7 years ago



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There are 507 posts in this topic. You are on page 2 of 11.
#51 6 years ago

Agreed. I don't like seeing 300mV ripple in the +12v line, but I haven't measured it at the amp yet

#52 6 years ago
Quoted from Matt_Rasmussen:

Personally, I think it's noisy power, but trying to track that down.

You guys just reminded me of something I did to my LAH years ago. It had quite a buzz in the speakers, which I at the time determined was coming in one of the power rails (seems like it was the +12). I connected inline a 10V linear regulator between the power supply and the sound board. Same concept as the choke / filter idea, but a regulator can have much higher noise reduction at the cost of a small voltage drop. This reduced the noise quite a bit (maybe 75%-90%) to the point that you can only really hear it if the room is otherwise silent. It had no affect on the minor display noise which is not loud enough to bother.

#53 6 years ago

I believe we are on the right track then. I also think I can create a simple inline connector for those who dont want to bother with soldering etc.

#54 6 years ago

Whatever you figure out count me in.

#55 6 years ago

Also, you might try isolating the sound board from the cabinet ground, the opposite of making sure your screws are all in place and tight. The sound board obtains ground from wiring through the connectors so it will operate without being grounded to the cabinet ground. Could be a ground loop problem.

The other thing is, the root cause of a sound problem may differ from machine to machine, location to location so a common fix may not apply to all cases.

#56 6 years ago

only hum I get out of DE games is the Display in attract mode. That about it.

#57 6 years ago

I have a solution. I'll be testing it tonite... just scrounging my parts bin for the right items. Maybe RadioShack will have what I need. I've cross referenced it with 3 other schematics (and a VCR), and sure enough, the values on the DE board appear to be wrong. muhaaahahaa.

#58 6 years ago
Quoted from castlesteve:

I have a solution. I'll be testing it tonite... just scrounging my parts bin for the right items. Maybe RadioShack will have what I need. I've cross referenced it with 3 other schematics (and a VCR), and sure enough, the values on the DE board appear to be wrong. muhaaahahaa.

Please let us know, I'm surprised that a new power supply didn't solve this though...

#59 6 years ago

Well..... here's what I have.

First I read the schematic and was thrown off. I read it that the 4 parallel capacitors were 4700uF 25V - which were way off. This should be 15000uF. So I put in another 10000uF and did some measurements.

1) without. I had 11.3V with 300mV AC ripple on the 12V. The voltage is low and the ripple is too high.

2) with added caps: My regulated voltage **dropped** to 11.2V but the ripple also dropped (as expected) to 150mV. The hum also was noticeably lower - but still present. I expected the DC voltage to increase though.

I was a little surprised at the lack of correction, then I looked at the values and each cap is 4700uF - so the total was almost 20kuF - which is more than enough for this rudimentary output. Looks like we have a design issue.

So, Matt - you are correct. This +12V output is the problem. I suspect that the original capacitors could be going bad (although I have a HUO Frankenstein with virgin boards). This can be solved by adding an external 12V regulator and bypass it entirely like you said. It would probably be easiest and still look mostly factory if you use a generic power supply. I will still probably replace the caps on this board anyway to see what happens... but my guess is that the sound board does not properly regulate and clean the unregulated +12v supply and expects a cleaner input.

this looks interesting

ebay.com link » Dc Buck Converter 10 15v To 0 9 12v 25w Step Down Voltage Power Supply Module

#60 6 years ago
Quoted from minnesota13:

Also, you might try isolating the sound board from the cabinet ground, the opposite of making sure your screws are all in place and tight. The sound board obtains ground from wiring through the connectors so it will operate without being grounded to the cabinet ground. Could be a ground loop problem.
The other thing is, the root cause of a sound problem may differ from machine to machine, location to location so a common fix may not apply to all cases.

I believe this is worthy of further investigation. I notice that if I loosen the mounting screws for the sound board the hum is lessened. Besides, Brett Davis of XPin has said that he has always heard the hum whether an original power supply was installed or one of his. I have one of his in my R&B.

viperrwk

#61 6 years ago

So we might actually be looking at 2 different issues here. I call TYFSBASI: Take Your Effen' Sound Boards and Shove It!

#62 6 years ago

Would a switching power supply like that introduce ripple as well? I'm no electronics genius certainly, but I seem to remember that is a negative property of that scheme?

#63 6 years ago

it easily could as it doesnt really offer any details on how clean the power is. Although a cheap experiment.

#64 6 years ago

Has anyone looked at how the amps are driven? In Stern's Whitestar system they are way overdriven and pick up a bunch of noise. You can tone it down by replacing a few resistors on the CPU/sound board. I've done it and it greatly helps. Details here:

https://groups.google.com/d/msg/rec.games.pinball/RiqCixRjptI/hwZcPUN2uoQJ

#65 6 years ago
Quoted from Matt_Rasmussen:

Would a switching power supply like that introduce ripple as well? I'm no electronics genius certainly, but I seem to remember that is a negative property of that scheme?

It's not a ripple issue, it's a noise issue related to the frequency of the switching, which can be mitigated by filtering the output and choosing a switching frequency that keeps the noise out of the audio circuit. Lots of AV equipment today use switching power supplies though I'm sure there are the purests who would prefer their AV equipment with a linear supply. Perhaps Brett will comment on what he does to filter the output on his PS.

viperrwk

#66 6 years ago

Someone just posted this, claims a new DMD solved his problem. But it's a Williams game, not Data East.

http://pinside.com/pinball/forum/topic/audio-feedback-hum-went-away-after-installing-nos-dmd-wcs94-wpc

#67 6 years ago
Quoted from Crash:

Someone just posted this, claims a new DMD solved his problem. But it's a Williams game, not Data East.
http://pinside.com/pinball/forum/topic/audio-feedback-hum-went-away-after-installing-nos-dmd-wcs94-wpc

That would be an easy check, turn on machine, listen to hum, unplug Power to the DMD. Either the hum goes away or not. You get an immediate answer.

#68 6 years ago
Quoted from Crash:

Someone just posted this, claims a new DMD solved his problem. But it's a Williams game, not Data East.
http://pinside.com/pinball/forum/topic/audio-feedback-hum-went-away-after-installing-nos-dmd-wcs94-wpc

It's NOT the DMD! I replaced mine and still have the hum...unplug the DMD, still have the hum.

#69 6 years ago

Viperrwk asked me to chime in on this thread. I apologize for taking so long to do so, but I wanted to review all of the schematics and wiring drawings I had for various games so I could speak directly to what I am 99% sure as to what is causing the hum described.

I am going to add a disclaimer though. What follows is based off theory and 18 yrs experience as a EE design engineer. I currently do not have any DE games in my collection so I could not go poking to verify my theories. If you choose to take my recommendations, and they work, please share it with the group.

I will address each component in the system, and by the time I get to the end, hopefully everyone will see how it is all connected.

OEM power supply
The original DE power supply creates a +12 and -12 unregulated DC voltage. For those who don’t know what an unregulated supply is, it is a rectified AC voltage is turned to DC and filtered with a big bulk capacitor. On the +12, the supply has 18000uf and the -12 has a 1000uf cap. The reason behind the 18000uf on the +12 is that this +12 is the input voltage for the +5V rail. If you replace both of these caps, the hum should be reduced. My recommendation is that to replace both with a larger capacitance value. These caps are bulk storage caps. They will decrease the ripple feeding into all of the downstream regulators. Simulations show increasing the 18000uf to 22000uf and the 1000uf to 1200 uf should increase the downstream regulator effectiveness by ~15%. Age and use have been working against us on these caps.

Comment on the XPin XP-DE5047
The XP-DE5047 also supplies unregulated +/-12, but there is a key difference. As mentioned above the +5V rail is generated from the +12 unreg DC. Unlike the OEM supply, which uses a linear regulator with a pass transistor to generate the +5v which is very inefficient (~55%), the XP-DE5047 uses a 92% efficient switching supply to generate the +5. It still has a large bulk capacitor on the +12, but it doesn’t pull as much energy out of the bulk cap to maintain the +5, so downstream ripple is still reduced.

OEM Sound board
This is probably the biggest culprit in generating the hum. The DE soundboard design takes the +/-12 V unreg DC and passes them to 7805(+5) and 7905(-5) linear regulators. The inputs to these regulators also have 470uf caps on them. In theory, what should happen is that they will work in conjunction with the bulk caps on the power supply board which should reduce the ripple even more. Solid theory, but there is more to this story.

In the mid-90’s most mfgs of 7805 and 7905 devices stated that they needed a minimum input voltage of at least 8-9 volts to maintain regulation. As far as linear regs go this is fine for the era. Modern equivalents claim they only need 7vdc to maintain regulation. If the ripple drops below the regulation point, the output of the linear will sag as well, so you now will have a 120hz signal on your output of the regulator.

The +/5V rails are fed into LM833 opamps, which will then transfer the 120 hz ripple into the MB3730 audio amplifier. I believe this is how the hum is getting there.

My recommendation for the sound board is to replace the 470uf (C31 and C52) caps on the inputs of these regulators with at least 1000uf caps. This gives you fresh caps, the increased capacitance will reduce ripple, which considering the age of the board, will allow it to keep the input voltage at a higher point, compensating for the higher electrical load caused by older components.

I would also recommend replacing the bulk caps on U31, U32, and U33. Primary power for these devices is the +12V regulated rail from the power supply. These caps (C60, C67, C74) should be replaced with the original value of 470uf.

DMD Display
The DMD display can have an impact on the hum as well, but only if it is a Babcock Plasma display. Why only Babcock? Babcock displays require 12V to operate which in DE games it gets from the power supplies regulated +12V. The internal structure of the SN75555 HV shift register used for driving the display counts on a stable +12V to properly bias internal transistors. Over time, I believe some degradation has also occurred with these parts because in theory, if the +12V is not rock solid, the ripple from the HV rails (60hz) can be induced on the +12V which can then be passed back to every device in the game using the +12V regulated rail, which includes the audio amps on the sound board.

Replacement of the 47uf cap at C18(?) should help this. I recommend a 100uf. No guarantee on this one because this path is also dependant on degradation of the SN75555 devices over time as well.

Summary
Not much to add other than I believe we are fighting an age issue. Keeping in mind that these games are 20yrs old, the electronics are feeling their age. A little refresh is always a good thing.

Brett
XPin Designer

#70 6 years ago
Quoted from XPinPinball:

Viperrwk asked me to chime in on this thread. I apologize for taking so long to do so, but I wanted to review all of the schematics and wiring drawings I had for various games so I could speak directly to what I am 99% sure as to what is causing the hum described.

Thanks for the write up. It's somewhat similar to what the EE at work told me.

Robert

#71 6 years ago

Hopefully not to wordy...we engineers tend to drag things out ;}

#72 6 years ago
Quoted from XPinPinball:

My recommendation for the sound board is to replace the 470uf (C31 and C52) caps on the inputs of these regulators with at least 1000uf caps.

C31 (470uf) is 50 volt and C52 (470uf) is 35 volt. Should these voltage specs be maintained when replacing them with 1000uf?

#73 6 years ago
Quoted from ChadH:

C31 (470uf) is 50 volt and C52 (470uf) is 35 volt. Should these voltage specs be maintained when replacing them with 1000uf?

You can always use higher voltage Caps than the original specs, if they physically fit on the board.

Newer caps are often smaller than their 20 year old cousins, so this is probably not a problem.

#74 6 years ago
Quoted from XPinPinball:

Hopefully not to wordy...we engineers tend to drag things out ;}

Not wordy at all, great job.

#75 6 years ago

The rule of thumb that I use with capacitor voltage specs is at least 2X of the actual voltage expected. For example C31 and C52 both have 12V input voltages so at a minimum use 25V caps. Larger is better and has no impact on the performance, but the larger ones should have a longer expected life span I feel.

Brett

#76 6 years ago

Had a similar issue on a Bally Silverball Mania.

Bad hum, replaced the cap that regulates the DC (C23 on the solenoid driver board) and poof - no more hum.

#77 6 years ago

Ok... so I've replaced all the radial electrolytic caps on the sound card with brand new ones. I even replaced C31 and C52 with 1000uf caps. Did not fix it.

I've tried unplugging the DMD to see if it made a difference. Did not fix it.

I've tried unscrewing the sound card and having it float. Did not fix it.

None of these have fixed my speaker buzz.

What to do? There HAS to be a solution.

#78 6 years ago

ChadH,

What about the power supply caps and C60, C67, C74 on the soundboard?

If you were local to Phoenix I would be there in a heartbeat with the tools of the trade. Where are you located at?

Brett

#79 6 years ago

Brett,

I did replace C60, C67, C74 on sound board. In fact, I replaced all electrolytic caps on sound board.

I don't think I have ever replaced any caps on the power supply. Which ones would be suspect? Or just replace all?

I'm in Illinois.

#80 6 years ago

Looks like those might get toasty from the heat sinks.

#81 6 years ago
Quoted from ChadH:

I don't think I have ever replaced any caps on the power supply. Which ones would be suspect? Or just replace all?

C1 and C4.

#82 6 years ago

I'll try that.

C4 is 18,000uf... not sure I have one of those handy, will have to see.

C1 is 1000uf, I should have a spare new one I can replace.

#83 6 years ago
Quoted from Jeff_PHX_AZ:

Check your boards have all the screws and they are tight. Loose/missing screws will cause this hum. I fixed my hum issue by putting in screws that were infact missing. Like you said it didn't do this hum until you got home with it, so maybe screw got loose or fell out. Always look for the obvious and easy stuff rule them out first!

+1 to this. My Laser War had a horrible hum, then we screwed down the screws on the sound board real tight and the hum went away.

#84 6 years ago

I'm just curious why a missing screw could cause a hum, aren't all the grounds connected together on the ground trace on the board?

#85 6 years ago

I replaced all the caps on the soundboard, with the manual suggestions, and a brand new XPIN power supply. I'll try replacing c31 and c52 with 1000uF and see if that helps, but I'm pretty sure it ain't.

Any validity to the post above changing out some resistors to lower the gain, the theory is that the output is just driven too high...

#86 6 years ago

I have the same problem with my tmnt. I've unplugged the DMD with no change. It does seem to be voltage related though. When in diagnostics and running bulbs checks, the more bulbs on the louder the noise.

#87 6 years ago

I surprised by this thread. This has been a known issue since the early 90s, and no one has ever been able to figure it out. My understanding is that is was just a weak design.

#88 6 years ago
Quoted from Atomicboy:

I surprised by this thread. This has been a known issue since the early 90s, and no one has ever been able to figure it out. My understanding is that is was just a weak design.

But then why do some Data East's not have the issue?

#89 6 years ago

Was just looking at the Power Supply on my Data East Star Wars...

There is a component on the board labeled VR1. On the schematic, it shows this as being a 7812. On mine, this part looks like it is broken off... it's gone and you can still see the base of the three legs of it.

I looked it up and this is a +12V 1A Three-Terminal Positive Voltage Regulator.

Is this part of my problem? I know 12V is involved with sound.

Or is this something that was removed at the factory?

Here is a link to the web information on found on the 7812:
http://oakbluffclassifieds.com/Old-Surplus-Listings/7812-LM340T12-12V-1A-pos-regulator-to-220-20-pack.aspx

#90 6 years ago
Quoted from ChadH:

Atomicboy said:

I surprised by this thread. This has been a known issue since the early 90s, and no one has ever been able to figure it out. My understanding is that is was just a weak design.

But then why do some Data East's not have the issue?

I have never come across one that didn't. Good luck though, if someone can figure it out, great, but this is just known as the DE noise.

#91 6 years ago

I too would LOVE some sort of fix / resolution to this issue.

One day.....

#92 6 years ago

Chad can you get a picture of that area? Either it has somehow broken off or it was never stuffed from the factory (most likely the latter). If this is that case that might explain your problem, according to castlesteve, who says missing +12v would cause it.

#93 6 years ago

I spoke with my friend about that missing VR1 component on the power supply, he looked at the schematic and figured that particular component was related to sending 12V to the display and not the sound board.

So now I tried another test... I unplugged the sound board CN2 connecter (the one that supplies +12V, -12V, +5V, and ground) and wired in an external power supply from a PC. With the external PC power supply, the game is PERFECTLY quiet! All buzz is gone! All noise related to the light matrix is gone!

So... where does this leave me? It tells me that the sound board is good for sure. The source of the buzz/noise is NOT the sound board. It MUST be the power coming into the sound board that is being fed from the power supply.

Earlier today I ordered all new capacitors for the power supply. I should get them next week. I will follow up with my findings once I replace all power supply caps.

By the way, here is a picture of the broken VR1 component.

IMG_4419[1].JPG

#94 6 years ago

Wow! So that means the X-Pin power supply isn't providing a clean voltage source either. Might want to check that out Brett and do some testing. Our Data East supplies and dropping like flies and we're down to just one working original. Would be really nice to have no hum when we order replacements!

You need to look at that 12v wave on the scope. I'm sure it's a mess.

#95 6 years ago

Well Crash, as far as I can tell, no, the XPIN supply isn't providing a clean source either. Which is strange right. No offense to the XPIN developers, but I paid good money...

#96 6 years ago

interesting thread, i too have a big hum in the speaker from my data east.

hope a solution is coming soon, will follow this thread closely.

#97 6 years ago

My JP has some hum not horrible but noticeable. I've recapped the sound board and helped a tiny bit. I've considered recapping the power supply but haven't done it yet. Hoping a solution is found. If not a separate power supply wouldn't be too bad especially if it's dead quiet.

#98 6 years ago

Not to sound redundant - but the issue is the power supply and nothing else.

Some supplies appear to exhibit less noise than others regardless of the newness of the caps and possibly bridge rectifier.

If you do not care about looks, you can easily drop in a 200W arcade power supply that will supply +12v and -12v (or PC power supply if you jumper the right connector to allow it to turn on without a button). They cost about $35 and should be good to go. Just connect the grounds together.

I'm personally out of interest now to try to solve or fix why the original power supply is deficient. It could be from overly noisy transformer or to various resonances in the circuit. Either way, we have a solution but not a fix at this time.

#99 6 years ago
Quoted from ChadH:

I spoke with my friend about that missing VR1 component on the power supply, he looked at the schematic and figured that particular component was related to sending 12V to the display and not the sound board.

Edit: Ignore, was discussing VR1 on the power supply, not the sound card.

Sorry, but your friend is wrong. VR1 is a -5v regulator (7905) that generates voltage used for the LM833 op-amps at U28 and U30. Install VR1.

#100 6 years ago

Just for kicks I need to listen to Hook really close as it has a replacement X-Pin power supply. I'll report back what I find.

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