ESU LokSound 5 58721, 58731, 58751, 58941 decoded

[peteski]

Back in 2018 I posted similar info about V4 decoders in this thread.  Here I will cover the new V5 decoders.

INDEX
 
Click on the link to go to that decoder's detailed info.

58721  LokSound 5 micro DCC Direct (for some IM, Atlas, and generic narrow-hood decoder)

58731 LokSound 5 micro DCC Direct Kato Japan (Kato EM13 format plug-n-play decoder)

58741 LokSound 5 micro DCC Direct Kato USA (for many Kato narrow-hood locos)  coming soon

58751 LokSound 5 micro DCC Direct  (for some legacy Atlas and IM locos, and other narrow-hood models)

58941 LokSound 5 micro DCC Direct Kato USA Widebody  (For E- and more recent F-units, F40, and similar)

[peteski]

LokSound V5 58721

This V5 decoder is a slightly reworked 73199 V4 decoder.  Most of the circuitry appears to be identical between those 2 decoders.  The outline of the PC board has been modified slightly. Track pickup pads have been deleted at the outside corners, and the inside corners in the inset areas have been made sharper.  The front and back of the circuit board has been made slightly narrower.  Electrically, the power sections (power supplies, motor driver, audio amplifier, voltage regulator, and other ancillary circuits appear to be identical to 73199.  The changed components are: the microcontroller chip, and some circuitry around it, and more AUX outputs have been added).  There are also more LEDs installed on-board.  Not sure exactly how useful those will be in custom installs.  Nice feature is that all function outputs are high-power, and most are accessible on solder pads on the board.

Here is a comparison of 73199 and 58721 showing just how similar they are.


ESU_73199_58721_compare.png


ESU_58721_Sound_decoder_dimensions.png



ESU_58721_Sound_decoder.png

For those who are interested I also drew a partial schematic diagram of the decoder. This decoder's design is different and more complex from other sound decoders I have dealt with in the past.  It has a power supply circuit with 3 voltage stages where a stay-alive caps or keep-alive module could be hooked up.

Stage 1: Raw rectified track voltage (marked "A" or RED on the diagram). This stage supplies power to the motor driver circuit, and to the next voltage stage (described below).  This is where one of the SuperCap-based keep-alive circuits could be connected to keep both, the decoder's electronics, and the motor powered during power dropouts.  This stage includes what looks like a Zener diode (for over-voltage protection?) and a very small ceramic capacitor (probably  few uF in value, to shunt any voltage spikes coming from the track).

Stage 2: (marked "B" or PURPLE on the diagram). The voltage from stage 1 is passed through a diode (same type of diode as used in the rectifier) to become stage 2. This stage has five multilayer ceramic caps used as a small stay-alive circuit (totaling probably less than few hundred uF, but since they are unmarked I don't know their exact value).  The voltage from this stage is then supplied to stage 3, and probably to few other circuits on the decoder (I didn't do a thorough trace to check what else is powered from this stage).  As shown on the diagram, since it passes through a diode, the voltage in this stage is just few tenths lower than the raw rectified voltage of stage 1.

Stage 3: (marked as "C" or BLUE on the diagram). Voltage from stage 2 is supplied to a 5.3V regulator which produces the stage 3 voltage.  There are two 100uF tantalum caps in this stage to act as a filter/keep-alive. This stage supplies power to most of the decoder's circuitry, including the audio amplifier.  There are also couple more voltages derived from 5.4V. One is 5.1V (not sure where it is used) and also 3V, which powers the "brains" of the decoder (the microcontroller and the Flash memory chip which houses the sound project files).  Voltage from this stage is also used as the common positive for all the decoder's AUX functions (including the V+ solder pad).  The designers of this decoder decided to use the 5.4V as the BLUE common-positive (instead of the usual rectified 12V track voltage used on majority of other decoders).

The tantalum caps in stage 3 (200uF total) do provide minimal protection from short-duration power dropouts, and there is also around 250uF worth of capacitors in stage 2, so we can't really say that the decoder has no stay-alives.  But all those capacitors provide bare minimum of the stay-alive capacitance.

Ground (common) of the decoder is marked on the diagram as "N".

Where to attach stay-alive capacitors, or a keep-alive SuperCap module?

The bottom part of the diagram above shows both sides of the decoder with color-coded locations of where the external caps can be installed.  The green circles indicate that the large copper areas are all connected to ground (common).

A capacitor, or a bank of capacitors, can be installed with its negative lead attached to any of the green marked areas or component pads (as there is no dedicated "ground" pad).  The positive lead can be hooked up to any of the red marked pads (for stage 1), or purple marked pads (for stage 2).  While I also show hookup locations for stage 3 (blue marked pads), I do not think that any additional caps installed in stage 3 will be helpful in keeping the sound uninterrupted and the model running.

A true SuperCap-based keep-alive circuit (hundreds of thousands of micro Farads with its built-in ancillary circuitry to limit the charging current and voltage) should be attached to green and red marked pads of the decoder. If installed there, it will power the decoder's electronics, the motor, and the function outputs. Since the RED pads on the decoder are very small and close to other components, one must be super-careful not to damage any components while adding the keep-alive circuit.  Unfortunately there is no dedicated RED voltage pad and the only attachment points are on small components, so it will require some precision soldering.

If the additional caps will be less than 1000uF in total capacitance then my recommendation is to attach them to the green and purple marked pads of the decoder.  Since the power-hungry motor is not powered from that stage, the keep-alive cap will supply power to the decoder's circuitry for a longer time. Hopefully the flywheels will keep the loco coasting through the intermittent contact spot while the decoder keeps on running and producing sounds.

Of course, any modification to the decoder are done at your own risk - it is highly miniaturized and delicate.


For those interested in more details, here are the locations of some of the decoder's main components.


ESU_58721_Sound_decoder_layout.png

I found it interesting that the rectifier diodes used in this decoder have a very low forward voltage drop (only 0.2V).  But I only tested it with minimal load so the voltage drop will most likely increase as the current draw increases. Still, they are probably Shottky diodes with the average voltage drop of around 0.5V or less.


MAP OF THE FUNCTION OUTPUTS AND THEIR SOLDER PADS


ESU_58721_Sound_decoder_functions.png

The above picture is self explanatory.
In factory-fresh decoders (with the default sound file installed), Aux 1-8 outputs are mapped to F3-F8 functions, so all the on-board LEDs can be turned on and off.

Nice feature of this decoder is that most of the AUX outputs (including headlights) are available as solder pads on the decoder. In the past, the headlight function outputs were not available on solder pads.  Only AUX7 and AUX8 do not have solder pads. Those are only connected to the on-board LEDs.

If someone wants to simply relocate the on-board LEDs while still using the on-board 680 ohm resistors, then unsolder the SMD LED from the PC board, then solder the wire lead extensions to the LED pads.  The LED polarity (anode or positive [A] and cathode or negative [C]) is indicated in the picture.

Instead of calling those 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 manual to get familiar with the AUX output mappings.  While the mapping can be done by individually programming a bunch of CVs on DCC system's programming track, this task is made *MUCH* easier using the ESU's LokProgrammer interface and software.

[ednadolski]

Nice!   Dziękuję!

Ed

[reinhardtjh]

Thank you for such a thorough dissection of the decoder.  I know this isn't easy.  I hope you can do the same for the 58741 Kato and when the Atlas legacy 58751 comes out, it as well.

[Jim Starbuck]

Outstanding!
Thank you very much!

Jim

[peteski]

Thank you for such a thorough dissection of the decoder.  I know this isn't easy.  I hope you can do the same for the 58741 Kato and when the Atlas legacy 58751 comes out, it as well.

You're welcome guys!

I actually did the dissection back when you lent me your decoder in February, but that was just handwritten scribbles. Then the write-up got buried with all  my other projects, and Jim's request sort of kicked me in the butt.  As I mentioned in the write-up, the design is very similar to 73199, so I was able to use most of that decoder's write-up. Yes, the plan is to cover the other decoders too.

[Steveruger45]

You're welcome guys!

I actually did the dissection back when you lent me your decoder in February, but that was just handwritten scribbles. Then the write-up got buried with all  my other projects, and Jim's request sort of kicked me in the butt.  As I mentioned in the write-up, the design is very similar to 73199, so I was able to use most of that decoder's write-up. Yes, the plan is to cover the other decoders too.

Thank you Pete. 👍😁

[jdcolombo]

Excellent info, Pete.  Thanks!

John C.

[dangerboy81]

Very Handy! Thank you!

[MK]

Nice!   

[peteski]

I had a request to post info about the 58731 decoder, so here it is.

Before posting the technical info I like to mention that my workbench became so cluttered that I had to spend several workshop sessions over the last couple of weeks decluttering it.  While not completely "cleaned", here it is, with the decoders being examined under the stereo microscope.  It is the first project done on the clean bench.  Don't worry @MK , it will not stay clean for very long.   

LokSound V5 58731

The LokSound 5 58731 is a decoder designed for plug-n-play installs into Kato models which are equipped with the EM13 format dummy DC plug.  Those are usually used in steam loco tenders, and also in some passenger MU models like ICE4 set.  As designed, that Kato's EM13 interface format is only for motor function, but the decoder also includes three hardwired function outputs (front/back headlights, and AUX1).


ESU58731_Sound_decoder.png

Here is a partial diagram of its power circuits. It is handy that ESU decided to provide the raw rectified voltage output (+U), or as it is often provided as the "blue" wire on other decoders.  It is normally used as the common positive for devices connected to the function outputs, and it is a perfect place to connect the positive lead of either add-on stay-alive capacitors, or even a keep-alive module.  Connecting additional capacitance to the B, C, or D circuits is not required or recommended.  I provided those details for informational purposes only.

The negative/common/ground connection is available on any of the green colored areas of the decoder.  My recommendation is to just solder the negative lead of a keep-alive device or capacitors to any of the gold-plated copper visible in the lettering strokes. If needed, the blue solder-mask coating can be carefully scraped to expose more of the copper area.



ESU58731_Sound_decoder_layout.png

This is the layout indicating the main components of the decoder (for informational purposes).


ESU58731_Sound_decoder_pads.png

Here is the info about the electrical connections. Handy when the decoder will be used in custom installs.  Note that the function outputs (headlights and AUX1) do not have any on-board resistors. Those have to be added externally.

I also included info on trimming the PC board if that might be useful in custom  installs.  I'm planning on trying it in the rear of a Kato wide body diesel (like E8). There is also likely a possibility to trim about 0.1" off the decoder's arms, but I have not confirmed it yet. It should fit nicely over the top of the metal chassis in the rear (while keeping the original Kato light board).


ESU58731_Sound_decoder_dimensions.png

And lastly are the decoder's dimensions.

With only 3 functions  is a rather simple decoder, but I think it might be useful in installs other than just what it was intended for.

[Dwight in Toronto]

Wonderful job Peteski, as always. 

I used this 58731 decoder in Kato’s GS4, using Kelley’s approach where the front smd led’s were replaced with bright white versions, and a rear led was installed in the tender.  I ventured into ESU’s flow-charting territory, and managed to configure the over-under front headlamps such that the first push of the ‘Headlight’ button turns on the lower lamp, the second push turns on the upper lamp, the third push activates the upper lamp as a gyro, and the fourth push turns both led’s off.  Sequential toggling of the one button is a rather elegant way to achieve numerous lighting effects without having to use several separate functions.  I have since implemented the same approach on a Kato E8 diesel with over/under headlamps.

I also used a 58731 to put sound in an N scale Model Power 4-6-2, and replaced the pathetically dim factory light bulb with an 0402 led. 

It’s a good little decoder for locos that don’t have any more than 3 lighting features, hence, well suited for steam.

[peteski]

Wonderful job Peteski, as always. 

I used this 58731 decoder in Kato’s GS4, using Kelley’s approach where the front smd led’s were replaced with bright white versions, and a rear led was installed in the tender.  I ventured into ESU’s flow-charting territory, and managed to configure the over-under front headlamps such that the first push of the ‘Headlight’ button turns on the lower lamp, the second push turns on the upper lamp, the third push activates the upper lamp as a gyro, and the fourth push turns both led’s off.  Sequential toggling of the one button is a rather elegant way to achieve numerous lighting effects without having to use several separate functions.  I have since implemented the same approach on a Kato E8 diesel with over/under headlamps.

I also used a 58731 to put sound in an N scale Model Power 4-6-2, and replaced the pathetically dim factory light bulb with an 0402 led. 

It’s a good little decoder for locos that don’t have any more than 3 lighting features, hence, well suited for steam.

Thanks Dwight!  I do recall your trials and tribulations with configuring those light functions both here, and on groups.io.

[Dwight in Toronto]

For what it’s worth, I just completed the installation of a third 58731, this time in a Dapol N scale 4-6-0 “Hall Class” British steam loco.  I picked up the loco from an Edinburgh hobby shop some 10 years ago, along with six beautiful Dapol coaches, as a bit of a souvenir while vacationing in Scotland. 

I had initially used a drop-in European 6 pin decoder to get it to run on dcc, and eventually replaced that with a small TCS wired decoder.  A few days ago, I started exploring the possibility of adding sound.

The challenge here is that Dapol puts the drive motor in the tender, which doesn’t leave much room for a decoder, let alone a speaker.  Remarkably, the 58731 was thin enough to lie on top of the motor, and trimming off the protruding legs yielded JUST enough room for an ESU 11x15 speaker/enclosure.  Trimming the legs meant having to carefully scrape off some blue enamel to expose new solder points for the orange & grey motor wires.  In fact, cutting back those ungainly, spindly legs actually yields a nice, compact, thin little decoder offering interesting flexibility and potential.

The 58731 only has 3 outputs, but this particular British loco doesn’t have any lights, so that simplified things somewhat. 
I would not have relished having to use, say, a full-featured Nano or Micro, and wasting all those outputs.  There’s a bit of consolation in only having to give up three instead (although one could always try to do a firebox flicker, if one was so inclined).

I was surprised to find that there are only three British steam loco sound files available for download from ESU.  I tried all three, settled on the one I liked best, tweaked a few things on the LokProgrammer, and now have a wonderful little British steam-driven passenger train characterized by that unique, high-pitched, piercing European whistle sound.

Anyway, suffice to say that the install was a success, and provided a challenging, fun little project.

[peteski]

Sounds good Dwight (and I mean this in more ways than one).

I never looked at ESU's British sound files, but I recall that ZIMO seems to have rather large selection of those.
http://www.zimo.at/web2010/sound/tableindex.htm
But most of those are only available as preloaded sounds (purchased with a decoder?).  Unfortunately many of ZIMO sound projects cost money or have other limitations.