Author Topic: S2000 Loud hiss from speakers (Read 1152 times)

JethroP · « **on:** January 17, 2021, 09:11:30 AM »

Recently acquired a replacement MPU and sound board (daughter board?). Picture attached. Reading previous posts I understand there was an issue with hissing that was resolved with the 504B board. Is this what I have? Also, I read to remove C57 and C59 on the sound board, as this often fixes sound problems, and advised these caps are not necessary. Well, I removed them and I had NO SOUND. I reinstalled them and have sound again, so they are definitely needed....but I have the hissing again. Suggestions?

Sorry about the picture quality, but this website doesn't allow me to post higher resolution pics.

Tilt · « **Reply #1 on:** January 17, 2021, 10:21:43 AM »

Can't read the part number on the board in the picture. Look for the last three digits of the part number on the board. It's probably a 502 Rev A.

C57 and C59 are only used for the auxiliary audio input (that 1/8" audio jack on the MML2 board). Removing them should not effect the SIMM sound, but won't fix a constant hiss sound either. When they start to fail you will usually popping sounds in one channel and loud intermittent static.

JethroP · « **Reply #2 on:** January 17, 2021, 11:32:40 AM »

I checked. The board is indeed 504b. So how to troubleshoot the hiss? It is coming from both speakers and I can hear it from across the room!

DB26 · « **Reply #3 on:** January 17, 2021, 11:35:50 AM »

Quote from: Tilt on January 17, 2021, 10:21:43 AM

Can't read the part number on the board in the picture. Look for the last three digits of the part number on the board. It's probably a 502 Rev A.

C57 and C59 are only used for the auxiliary audio input (that 1/8" audio jack on the MML2 board). Removing them should not effect the SIMM sound, but won't fix a constant hiss sound either. When they start to fail you will usually popping sounds in one channel and loud intermittent static.

I can add that I have removed C57 and C59 from two sound boards and it did not cause any problems.

Tilt · « **Reply #4 on:** January 17, 2021, 12:01:21 PM »

Quote from: JethroP on January 17, 2021, 11:32:40 AM

I checked. The board is indeed 504b. So how to troubleshoot the hiss? It is coming from both speakers and I can hear it from across the room!

That's not normal for a 504 Rev B board. Is the hissing coming from one channel or both?

JethroP · « **Reply #5 on:** January 17, 2021, 12:05:02 PM »

It is coming from both channels.

Tilt · « **Reply #6 on:** January 17, 2021, 12:24:37 PM »

You could try replacing the MML2 board and see if that fixes it. It's the cheapest thing in the chain list of possibilities to do. Do you have backlit reels?

Stayouttadabunker · « **Reply #7 on:** January 17, 2021, 01:11:38 PM »

Quote from: JethroP on January 17, 2021, 09:11:30 AM

Sorry about the picture quality, but this website doesn't allow me to post higher resolution pics.

you can post up 1000kb...I think your pic is like 146.96 kb ?

JethroP · « **Reply #8 on:** January 17, 2021, 01:20:06 PM »

I do not have backlit reels.
I do not have another MML board. 😩

Tilt · « **Reply #9 on:** January 17, 2021, 01:24:41 PM »

Ok. Backlit reels created a lot more background hiss. I was going to suggest that you unplug the power to the back light controller and see if it reduced it or not.

JethroP · « **Reply #10 on:** January 23, 2021, 03:38:37 PM »

So I tried another MML board and that didn't make any difference.
Then I tried another amplifier board (the one in the top box) and that didn't make any difference.

Any other suggestions?

Stayouttadabunker · « **Reply #11 on:** January 23, 2021, 03:59:36 PM »

Return board to seller

JethroP · « **Reply #12 on:** January 23, 2021, 04:01:47 PM »

Quote from: Stayouttadabunker on January 23, 2021, 03:59:36 PM

Return board to seller

Which one?

Ken · « **Reply #13 on:** January 23, 2021, 04:31:29 PM »

Try another speaker.

JethroP · « **Reply #14 on:** January 23, 2021, 04:40:47 PM »

Quote from: Ken on January 23, 2021, 04:31:29 PM

Try another speaker.

It's coming from both left and right speakers.

Stayouttadabunker · « **Reply #15 on:** January 24, 2021, 08:44:36 AM »

Quote from: JethroP on January 23, 2021, 04:01:47 PM

Quote from: Stayouttadabunker on January 23, 2021, 03:59:36 PM
Return board to seller
Which one?

You changed out the MML boards, audio amp board and still have the hissing.
I think your main 504 MPU is screwed up bad.
The 504's is supposed to have the fix that clears up the hissing problem that the earlier 502 boards had.
The problem with putting in resistors on the speaker wires up there makes the audio amp worker harder.
I remember soldering in resistors once and the small amp board overheated.
Offhand, I don't remember exactly which resistors worked best.
There's documentation on this in the S2000 forums somewhere because this was a common problem everybody had with the 502 MPU's.
I've never seen this hissing problem happen with a 504 MPU.

The only thing I can possibly think of as a way to try to fix this is to wrap your speaker wires with tin foil....haha
or send that MPU back.

JethroP · « **Reply #16 on:** January 28, 2021, 09:47:08 PM »

Tried isolating the speaker wires away from the power wires. No help. Ended up with a workable solution by installing one 47 ohm resistor in series to each of the two upper speakers. Hiss is all but gone.

Billdozer · « **Reply #17 on:** February 01, 2021, 05:17:17 AM »

Is this what you used wired into the white wire?

https://www.parts-express.com/47K-Ohm-1-2W-Flameproof-Resistor-10-Pcs.-002-47K

JethroP · « **Reply #18 on:** February 01, 2021, 06:23:01 AM »

Quote from: Billdozer on February 01, 2021, 05:17:17 AM

Is this what you used wired into the white wire?

https://www.parts-express.com/47K-Ohm-1-2W-Flameproof-Resistor-10-Pcs.-002-47K

Yes

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Author Topic: S2000 Loud hiss from speakers (Read 1152 times)