ESU 58751 LokSound 5 Micro Direct NMRA DCC Sound Decoder - Decoded

Last Updated 231223

ESU 58751 LokSound 5 Micro Direct NMRA DCC Sound Decoder - N Drop-in Board for Pre-2016 Atlas Narrow Hood type

Originally posted on The Railwire: A Forum for Modelers by user peteski, last updated August 03, 2023, 02:46:30 PM.

This information is shared by and republished here with permission of author.


ESU 58751 LokSound decoder for legacy Atlas, IM, and other narrow-hood models

 This V5 decoder is a slightly reworked version of a 73100 V4 decoder.  Most of the circuitry appears to be identical between those decoders.  Electrically, the power sections (power supplies, motor driver, audio amplifier, voltage regulator, and other ancillary circuits) appear to be identical to 73100.  The microcontroller chip, and related circuitry around it are the changed components. A new feature on this decoder is addition of solder pads for connecting ESU's Power Pack 3-wire keep-alive module.  Those pads also make it easier to add any standard 2-wire keep-alive.


Here is a comparison of 73100 and 58751 showing just how similar they are.


Dimensions of this decoder are also same as that of 73100


For those who are interested,  I'm including a partial schematic diagram of the decoder, along with access points to various voltages.  It is included it for informational purpose only, since this decoder already includes solder pads for connecting Keep-Alive module (or individual capacitors).


Here is the component's layout.


Identification of decoder's track and motor pads.


This decoder includes full-power (not logic level) outputs for AUX3 and AUX4 with no resistors.  But no solder pads are provided for AUX1 and AUX2 outputs which control the on-board LEDs. To add external LED to those outputs, the on-board LEDs would have to be unsoldred, and the LEDs cathode pads would be used as the output pad.  Again, no resistors on the cathode side (in-line resistors are on the anode side).

The Power Pack Control (PPC) solder pad is used to control the ESU's Power Pack Keep-alive unit when the decoder is being programmed on the programming track. While in other N scale decoders (like the nano) the PPC pad has to be selected from one of the available logic-level AUX outputs, on this decoder the PPC pad is dedicated to that function.  It does not show up in the Physical Outputs section in LokProgrammer. Hardware-wise it's just an undocumented logic-level AUX output. Again, the rather sparse info in the ESU manuals does not really provide much detail, probably because it is always enabled.  If not being used there is no problem leaving it disconnected - the decoder will not be damaged.

The ESU Power Pack connects as follows: "-" is the common pad (black wire), "PPC"  pad is the control signal (white wire), and "+U" is the positive voltage (red wire). If just attaching a large value capacitor, it connects to the "-" and "+U" pads.

Instead of calling the outputs "functions" like most DCC manufacturers do, ESU calls them "AUX" outputs.  This is likely due to the fact that all these outputs can easily be mapped to any DCC function.  The output mapping feature on the ESU decoders is much more flexible than on most typical DCC decoders from American manufacturers.  I highly recommend thoroughly reading through the ESU decoder and LokProgrammer manuals to get familiar with the AUX output mappings.  While the mapping can be configured through individually programming multiple of CVs using DCC system's programming track, this task is made *MUCH* easier using the ESU's LokProgrammer interface and software, or at least JMRI DecoderPRO.