A friend just dropped off a Bachman C27 loco that he got second hand. I checked it over and it has a digitrax motor decoder and a soundtrack HO sound decoder. This guy is running MTS so track voltage will be around 22-24 volts. Will a HO decoder handle that? The original owner must have been running something at a lower voltage.
I guess we could lower the voltage to the MTS control box if necessary.
David
There are HO decoders that meet/exceed the G scale specs.
The Zimo MX640 and MX621 are a good example as some have a 35 volt spec with a 50 volt overshoot spec.
I use these in the gustav handcar and rail trucks where the current will always be low.
I will have to check to see what the limits are for this soundtracxx decoder.
No markings on the decoder. I read out cv 8 and got 141 which is throttle-up soundtraxx.
It works ok but I have my power supply set at 13 volts.
Do you intend to just replace the sound decoder?
If you do, remember some sound decoders need to “see” the motor in order to make the sounds follow the speed/load.
As Dan says, low current operation allows “HO” decoders to be used in “G” scale equipment, but I don’t believe that the C27 will work in the situation Dan describes, driving the motor.
I do believe that the Zimo will “throttle” up with no motor load connected.
I’ve use the various Zimo MX64x units with success on very low current G scale locos too, like the Accucraft Casey Junior, MTH speeder, Berlyn Casey Jones, etc.
Greg
There is a digitrax decoder controlling the motor and loco lights.
The soundtraxx decoder is only for sound and tender light.
It is set for same address as the digitrax decoder.
Sound functions, chuffs work fine up to 18volts.
The mts system is 22 volts and overloads the decoder.
Unless the guy wants to change his power supply for the mts he
will need to change out the sound.
David
if loco speed is adequate, try a bidirectional “voltage dropper” made of diodes to drop that track voltage down… all you need to do is cut one track pickup lead and insert the “dropper”…
Greg
Greg,
The motor decoder is fine. I would only need to drop the voltage for the
HO sound decoder in the tender. Not sure what a voltage dropper is.
Will the dcc signal travel through it to trigger the functions?
David
Yes, will travel just fine:
(right hand circuit)
(http://elmassian.com/images/stories/electronics/misc/dropper.jpg)
Thanks Greg, I will try it.
Will 1N4004 diode work?
David
I’d use a schottky, since you want to preserve the integrity of the signal…
Look for one of an appropriate amperage.
I have seen the 1n400x series work, but I’d try for the Schottky first.
Greg
I used the 1N4004 and the voltage dropped from 22v to 19.3v.
Decoder and functions work ok.
Can I get a little lower?
Another diode or different diodes?
David
You can add as many diodes in the “center string” as you want.
That’s the beauty of the design, when you have to drop a lot of voltage, it’s fewer diodes… the “bridge” around them allows the single string to drop voltage in “both directions”.
Greg
