S2000 speaker hum when reels are spinning

[Wadsworth]

I spent all day getting a "Secrets of the Tomb" running today, but ended up with a very annoying speaker hum when the reels are spinning (not with payouts).  The hum is independent of the volume, i.e. if I turn the volume down, the hum is just as loud.  I've read a number of old NLG posts addressing this issue, usually recommending putting a resistor in line with the speakers.  It seems to me this is treating the symptom, but not the cause.  Does anybody know why I have a hum (jokes aside)?  I have swapped reels, in-line amplifier, power supply, multimedia boards and sound SIMMS to no avail. I also tried putting chokes on the reels and amplifier inputs.  Could it be in the chips, MPU or backplate??  As it is...I have a pretty machine that sounds terrible.  I know I'm a noob, but can anybody help?

[rokgpsman]

Probably the reason all the people in those old posts resorted to installing a resistor in line with the speaker was because all the previous owners with this problem and others looking into it were not able to solve the problem otherwise. Perhaps someone here will have another thought to try but you've eliminated all the possibilities I can think of.

The problem may have to do with the reel stepper motors inducing noise into their power supply line, it gets back into the power supply and then gets over to the audio circuitry and you hear it. But that's just a guess, and I'd think the filtering in the power supply would prevent this. To really investigate it you could take a separate power supply and run just the audio circuits off of it and see if that changed things.

Do you have another S-2000 that does not do this? If so it would seem possible to eventually find what is the cause, including good grounding wires, wire placement as it runs about the machine, corroded connectors, etc. After swapping the main assemblies it leaves the weirdo stuff to try.

[cowboygames]

Which version MPU do you have installed? A lot lot of people have resolved it by using a 504B or 1270 enhanced board. Even IGT couldn't fix the problem versions of the board without redesigning it somewhat. The factory workaround on the older versions didn't help much.
I was going to suggest mechanical noise from the reels themselves, which you can get if they are worn or the strips aren't snug, but you said you changed the reels already

[Wadsworth]

I'm not with the machine now but I know the board is a 500 series without labels (i.e. don't know if it's a 502, 504, etc.).  I have other S2000's without a hum, but haven't tried swapping to see if the hum follows the mpu and software.  Would you recommend that as my next step?

[rokgpsman]

Swapping the mpu would be fairly easy to do and it could verify your machine has the problem cowboygames mentioned. If that's it you'll see why some people install the resistor instead of spending for another mpu board.

[qbert]

Just put a 504 board in and your problem will go away.
You can play with resistors if you want but the hum will still be there in the background.
Rich

[cowboygames]

For clarification, it would need to be a 504B, a 504A will still have the issue. A sure way to know this is your problem is to remove the multimedia board and see if the problem goes away. All the ones I encountered only had the problem when a MMLII board was installed, simm or no simm didn't matter and removing the board removed the problem, but I chose to have the enhanced sounds with the simm card so I used either the resistor solution or swapped to a board that worked. I used 10ohm resistors on ALL speaker leads, both + and - as the problem originates through the grounding circuit

[rokgpsman]

Will the bad mpu boards (such as the 504A) do this in any S2000 chassis, with any software chips installed? It's not all 504A boards do this, just some, right? Does adding that MMLII board put the board very close to a wiring cable bundle that would be farther way otherwise?

I'm wondering how they ever got out of the factory, seems like they would have failed final test? Was the noise low enough to not be heard in casino environment, only became a problem for home user?

[cowboygames]

It's all 504 boards other than the 504B and the issue seems to be with grounding through the MMLII board. All the different board versions I tried lost the problem when the MMLII was removed. Most casinos solved the problem by not using enhanced sounds or MMLII boards

[CVslots]

You guys are spoiled...no IFs, ANDs, or BUTs about it! Yes, some board revisions give a slight hum, but it's not like its deafening. And dont refer to any board but a 504B as a "bad" board!!! They perform perfectly! The 501 and 502 boards work just fine when in a normal room, with average background noises. You guys act like you can't hear the TV because of the hum! If you keep pushing this issue, 504B boards are gonna be $125-150 a pop, as youre really only dictating your own market on them. The boards are just not that easy to come by in casino loads. It all depends on the timeframe the machines came from IGT (as IGT is oblivious to the noise issue, since in an actual casino setting, this "hum" is not an issue). Many, maybe even the majority, of S2000s have left the casino floors already...these 504B boards are not going to be plentiful going forward. Better get them while you can, as they will not be around forever.

As for those you who think I'm saying this as a vendor of the aforementioned boards, I do not have either board avail right now, so KMA...

[rickhunter]

I have switched to enhanced boards on both my S2K's, no hum at all.  I have a pair of 504B's that I'm keeping along with some 502's, just to have the "complete" set of hardware.  I'm such an parts wh#r?, it's embarrasing. 

[CVslots]

You are the parts wh#re you claim to be...as are many others here, but they won't yet admit it, lol! They are not too the embarrassed stage yet, only the ashamed stage...

I just hate to think what's gonna happen in a year or two when someone asks for a 504B board...they are gonna hate me for the price they are commanding. No one knows outside of NLG...I can almost guar are that. If your shopping games for sale, that him isn't going to matter, not to you, or the customer...