Problem reading XLS CVs with Massoth PC Module

[Diesel2000]

I'm having a strange problem with a new Massoth PC Programming module. The CV values returned from XLS decoders are not correct. I have no issues with an M or LS decoder and am even able to load and update firmware and sound files on the XLS. I am able to read the XLS values correctly from the CS using the MST, so I dont think there is an issue with the decoders themselves. Its the same problem with 3 different installed XLS decoders. I tried using different power supplies with the PC Module from 2amp-10amp but nothing has improved. Massoth is stumped and has asked me to try hooking the programming track output directly to the track inputs on the decoders, but I have not opened up a loco yet to try this. Has anyone encountered anything like this?

 

[Greg Elmassian]

Yes, it can be a number of things. Assuming you are talking NMRA service mode (programming track)

extra loads directly across the track pickups that interfere with the low power service mode commands (lights, extra decoders, smoke)
keepalive on the decoder
extra resistance in the path (long leads on the programming track, trying to use rollers, dirty rail, poor power pickups)

Do what they suggest first, that will cut your possibilities in half and quicken your path to the answer. (unless you have left smoke or lights on)

Greg

 

[Diesel2000]

I finally solved the mystery of reading incorrect values from XLS decoders with the PC Module. The issue is the buck converter I am using in all 3 of those locos to drop the voltage from DEC+ to run the LEDs I've installed. I use these to bring track power down to 3.1V for the 3mm LEDs I've instead of just using resistors. They allow me to dial in the voltage exactly for the brightness I want.

https://www.amazon.com/Valefod-Efficiency-Voltage-Regulator-Converter/dp/B07T5X5LSH/ref=sr_1_1?dchild=1&keywords=valefod+buck&qid=1629814110&sr=8-1

Once I disconnected that from DEC+ on the XLS decoder then the PC module read all the CVs correctly. This seems bonkers to me because the CS does not have the same problem trying to read the CVs from those XLS equipped locos with this buck converter attached.

Interestingly a Stainz with an LS decoder in which I have installed a mini buck converter for the LED voltage in the same way does not have an issue. For that I'm using this one:

Amazon.com: EBL Buck Converter MP2307DN DC-DC Voltage Regulator 3A Power Supply Step Down Module with Voltage Regulator 4.75-23V to 1.0-17V(6 Pack) : Electronics

Buy EBL Buck Converter MP2307DN DC-DC Voltage Regulator 3A Power Supply Step Down Module with Voltage Regulator 4.75-23V to 1.0-17V(6 Pack): Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[Greg Elmassian]

Perhaps a ferrite bead on the input to that converter, sounds like it is feeding noise back into the decoder.

Greg