I bought an Southern Pacific AC12 cab forward off Ebay and it was delivered on 1/25.
The engine when at idle on the track has a constant sound coming from the speaker. This sound is rather loud and annoying. This sound never changes tone, pitch or volume and does not sound distorted. When the engine is running the chuff, bell, horn, etc. all sound fine, but the above sound is still present even when the engine is running down the track. I sent Intermountain and email and have not heard from them.
To anyone who has one of these, is this sound normal for one of these Intermountain engines? If this were a diesel engine I would think that it is the sound of the diesel engine at idle on a siding, but since the sound never changes it does not sound to me like any kind of engine at idle.
A description of the sound would be helpfull, meanwhile I offer this possibility, later classes of cab forwards vented their air compressor exhaust directly into the atmosphere producing a distinctive weezing sound unique to no other steam engine, although the exhaust note should change in pitch and volume, could this be what your’e hearing?
Below is the same answer I gave you in the Yahoo SoundTraxx forum.
Sounds like the air compressor pump. With my Tsunami decoders, the pump
action dows slow down if the loco is sitting still for a short while. Try
adjusting the CV for the air pump level. I have done that with the Tsunami
decoders. Go through the list of CV’s for all the possible sounds and play with them.
Are you aware of all the sounds this loco could have?
I have one of the new AC12’s and the sound is a normal Tsunami steam sound. It does have the air pump sound that is for the AC12 only. If you have some other sound and it cannot be reset, it should be sent back for replacement. Function 4 has a steam release sound. Have you tried to use the CV 8 set to 8 and reset the sound unit??? Does it run OK?? That can be a problem with the AC12, even the new ones.
The prototype AC 6,7,8,10,11 and 12 Cab-forwards had what is referred to as ‘talking pumps’ that released their air directly into the atmosphere. The pitch was fairly constant, and a kind of ‘signature’ for these locomotives. Occasionally they’d get out of synch and ‘answer’ each other.
This could be the background noise you’re referring to. If so, it’s part of the sound.
You’ve probably never heard a real AC12 or any of the other Cab Forward locomotives. The air pumps had a very distinctive wheezing sound. The pumps exhausted their steam upwards right behind the smoke stack and it was a very loud sound.
If you leave the model on the track long enough, the sound should slow in tempo and eventually stop. Download the decoder technical reference manual from SoundTraxx and there should be a CV that can be adjusted to quieten and or stop the sound if you find it too annoying.
Hi Rod. I have been working on one also. Right out of the box, no changes to any programing, the sound is like a sharp gun shot. At idle it repeats about once a second or so. I think i will try the factory reset and see if that helps. If you find the cure please pass it on. Kind of a let down for a $500 loco. Mike
What you’re describing is definitely the sound of the air pumps. There’s nothing wrong with your model. The real Cab Forward made that sound. The only thing you might be able to do is turn the volume down on that particular sound if you don’t like it.
I agree. I routinely adjust individual volumes with a new decoder, or one on which I have had to perform a factory default restoration, but that means getting into the manual and learning which CV’s control which effects.
I have learned a few years ago to never believe DCC will work correctly out of the box, especially sound. The sound decoder people are technicians, engineers, will probably no idea about proper sound levels for different scale locomotives.
Unfortunately I have now found out that the Intermountain cab forward has serious problems with the motor and drive train. Mine will not go over 30smph and I am sending it back for a refund.
To bad, I have wanted one of these Intermountain first released them two or three years ago, how ever long it has been, but I am not going to replace the motor and spend 8+ hours fixing Intermountain’s manufacturing and design problems.