# Marklin/LGB MSD3 mfx/dcc/analog Sound Decoder: Voltage Buffer?



## LGB333$$$$ (Oct 11, 2017)

For Dan Pierce or Greg Elmassian Engineers - Below are photos of the MSD3 sound decoders installed in the currently produced sound decoders in LGB locomotives. The Marklin documentation indicates these decoders have a Voltage Buffer ".....that allows you to keep the sound operating in short areas of track without voltage." I don't see any regular power cap capacitors on these boards, can you identify where the voltage buffer is please?
Thanks
Tom


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## Greg Elmassian (Jan 3, 2008)

So they say there is a voltage buffer on the stock board somewhere... I would look for large monolithic smd caps, how about the other side of the board?

Also, it could (and most likely is) very small, otherwise, why would they outfit the board to take a much larger unit?

Greg


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## LGB333$$$$ (Oct 11, 2017)

Greg Elmassian said:


> So they say there is a voltage buffer on the stock board somewhere... I would look for large monolithic smd caps, how about the other side of the board?
> 
> Also, it could (and most likely is) very small, otherwise, why would they outfit the board to take a much larger unit?
> 
> Greg


Greg, I've attached a couple more photos of the decoder, the underside of the board and the base plate with the decoder board removed. I sure don't see any "voltage buffers"!


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## Greg Elmassian (Jan 3, 2008)

Well buffer = capacitor

There are several, but it looks to be the standard configuration, there is a full wave bridge from the track, then some filtering, then a voltage regulator and a little less filtering.

It's possible they claim the filtering on the rectified track voltage and the filtering on the 5v regulated supply to be a "buffer"... 

what are the voltages and farads of the 2 sets of capacitors?

Greg


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## Dan Pierce (Jan 2, 2008)

My guess is the 5 identical larger capacitors and like Greg I am interested in the markings on the side of the caps which denor=tes voltage rating and capacity. All of my LGB engines (non-Marklin build) had super caps for sound backup only.


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