Roco 72155 USATC 2610 Zimo Decoder MX645?? - Random Blow-Off Sound Too Loud

[Tim_CO]

Greetings and happy holidays from Colorado, USA. I apologize in advance for being overly verbose, but generally more data is better when troubleshooting.

 

Please note this is my first post in RMWEB so I'm hoping I'm posting in the appropriate subsection.

 

I've recently been working on a UK circa 1940 wartime layout in OO/HO. I would consider myself fluent/expert in most US based DCC sound decoders. However, I'm struggling with tuning some of the European decoders. Any assistance you could provide would be sincerely be appreciated.

 

I recently purchased a Roco 72155 USATC 2610 with factory Zimo DCC & Sound. The first thing I did after receiving the engine was to upload the default configuration to JMRI which detected the decoder as one of several MX645 variants. I initially chose MX645P22 as that's what's listed in the included manual. 

 

The engine is functioning well in all aspects but one. There's a random "blow-down" type noise that is easily 3x the volume of everything else on the engine. It's so loud I don't like being in the room when it happens. It's making the engine unpleasant to use. This noise is different from the blow-down sound on F17.

 

I've tried turning off literally every sound available in JMRI and I've adjusted the value for CV 584. The volume will not change. 

 

I took out the decoder to confirm it is indeed 22 pins and discovered its actually 18 pins and is centered in the receptacle (as opposed to being all the way left or right). CV 250 lists 221 which the PDF manual indicates the MX645?? family. 

 

When I do a hard reset CV8=8, the sound occurs less frequently but it still happens. The sound occurs with the engine is moving and static.

 

Please help me quiet down this engine so I can use it on my layout. 

 

I've attached images of the installed decoder. I can't find any identifying information. 

 

Thanks in advance.

 

Tim

 

Edited December 23, 2023 by Tim_CO

[pauliebanger]

Hi Tim,

I'll try to help but I don't know this loco or the sound project. 

I can make some educated suggestions.

The decoder is a ZIMO MX645P16. This is identical to the P22 decoder hardware and software but has reduced access to some function outputs due to the reduced pin count.

One of the loudest sounds on a steam loco is when the safety valves are lifted, so this may be the sound you are hearing.

The random sounds aren't listed in the Roco docs, so you'll need to experiment.

The random sounds can be adjusted with CVs in the range 744 to 767, but this covers 8 possible random generator slots.

Assuming the slots have been filled lowest number first, try these volume CVs in this order - 745, 748, 751, 754, 757, 760, 763 and 766. You may need to cycle power to the model between each attempt before you hear any change, depending on your equipment.

The valid value range for these CVs is 1 to 255, lower value gives lower volume.

Check out the existing values for these CVs and set lower values until you achieve your preferred level.

 

Paul 

 

 

[Tim_CO]

pauliebanger - Thank you for the tips. 

 

I changed each of those CVs to 0 and it's still happening. Any other thoughts?

 

Tim

[pauliebanger]

Try using values within the range I suggested. (1-255).

Value 0 is not a valid sound attenuation value so has the same effect as using 255, max volume.

That is to say, the lowest volume is achieved with value 1 in the volume CVs.

When you have established which CV changes the volume of the sound you wish to change, come back with it and I or someone will be able to tell you how disable this particular sound altogether if that's what you would prefer.

Paul 

Edited December 24, 2023 by pauliebanger

[Tim_CO]

Paul, 

 

It would appear you've resolved my issue. Well done and thank you!

 

I've literally been working on this for days. It would've never occurred to me to set the value to 1 instead of 0.

 

Tim

Edited December 24, 2023 by Tim_CO
Well vs we'll

[Tim_CO]

Should another poor sap run into this same issue in the future, the magic CV is 757. 

[pauliebanger]

Glad you found your solution. I'm a little surprised that it was such a high numbered random generator, but that's decided by whoever created the project.

Whilst that CV can only be guaranteed to be correct for this specific project, the range of CVs to experiment with will remain the same, so anyone with similar problems with random sounds can follow the same procedure to find the relevant volume CV.

 

Paul 

Edited December 26, 2023 by pauliebanger