Hi all,
I just recently purchased an HO Sound Value USRA 4-6-2. I read the thread at https://www.bachmanntrains.com/home-usa/board/index.php/topic,35808.0.html and I saw no mention of the Chuff exhaust rate. I was wondering if anyone else had this engine and had changed and fine tuned the Chuff Rate.
Thanks
See https://soundtraxx.com/content/Bachmann/SoundValue/HOScaleSteam/bachmann_ho_462_sv.pdf
The default value of cv 131 is 75. Steam engines had 4 chuffs per driver revolution. The sound Value decoder will never be chuff-count perfect at all speeds so what you are looking for is to be minimally off that number at the most number of speeds below 4 or 5 steps on a 28-step system or 10 or so out of 128 steps on other systems like NCE such as I have. Above these speeds the engine is going too fast to count the chuffs anyway.
Put your engine on the track and run at either 4 or 10 steps depending on your system. If the chuff count is less than 4 at the cv default value of 75, most likely, adjust upward in increments of 10 until near 4 per turn, then fine tune. Historically over time, tuning cv's on over 50 engines, I've found that a cv 131 value around 150 often works, though I've had some as low as 125 and others sometimes around 175. Try this process and these numbers and report back.
its been a while since i did mine, but as i recall it was roughly 85 to match closely at "road speed". its a tad fast at crawl but really close at speed.
FWIW, I try to match the 4 chuffs per revolution at fairly low speeds. Once you get up to "road speed" you can't really see whether the rate is exactly 4 per rev, whereas at low speeds you can see if the chuffs and revs are in sync.
Quote from: ebtnut on October 17, 2019, 11:44:10 AM
FWIW, I try to match the 4 chuffs per revolution at fairly low speeds. Once you get up to "road speed" you can't really see whether the rate is exactly 4 per rev, whereas at low speeds you can see if the chuffs and revs are in sync.
I think it depends on how you run it. i very rarely have the pacific crawling, it spends 90% of its runtime at speed step 50/128, stock motor CVs, so thats where i matched it, and i can definitely tell that its in sync. for a switcher, if i HAD any with sound, i'd match lower.