decoder question

[dave9999]

I have LL proto-2000 FA1 and FB1 with decoders installed. Both have digitrax decoders.
My problem is that they now run at different speeds. Also one will try to start before the other!
I have loaded identical speed tables and even tried ajusting start,mid,and max voltage.
I can get them close but not to the point where they run the same.They ran perfectly in
sync under dc power. Also I reset both decoders and tried again. Same result.
The A unit has a DH163 decoder and the B unit has a DH123,so both have the same
current rating which I believe to be 1.5 amps. Any ideas?

[cacole]

If I understand Digitrax' decoder numbering scheme correctly, the only difference in these two decoders is the number of functions they support (6 vs. 2), so they should run the locomotives at the same speed if you have the start voltage and speed tables the same. Check to make sure you don't have one set for 14 speed step and the other for 28/128 speed step -- this will cause them to run at different speeds. If that doesn't help, use their built-in speed tables instead of loading your own. A last resort guess is that you might have a wire from one decoder rubbing against a flywheel or drive shaft and causing it to run slow. Re-check all of the wires and tape them away from the drive train if necessary. By the way, Digitrax' decoder numbering scheme is as follows: D for Digital; H for HO scale; 1 is the motor current rating in Amps; the fourth digit is the number of functions supported; and the fifth digit is the Digitrax series number. In your case, both are Series 3 decoders (the most recent release).

[dave9999]

I have already tried loading the built-in speed table , same result. No wires are making any contact
with the fly wheel or driveshaft. This may sound crazy ,but is it possible to wire both locos to the
same decoder by way of dcc plugs.Is there enough power to run both locos? Will I do damage to
locos or decoder? Just an idea. I was thinking of adding a soundtraxx decoder. But I need to get this bug work out first. Thanks, Dave

[Anonymous]

First of all the decoders.

The DH163 is not the same as the DH123. The 163 has a feature called scaleable speed stabilization which tries to keep the loco at a constant speed as it goes up and down grades. This feature is controlled in CV's 55, 56 and 57. I have both 163's and 123's and do not MU with these different decoders. Confusing - I MU 123's together and MU 163's together -- I do not MU a 163 with a 123.

In theory you should be able to power both locos from a single decoder as long as you don't exceed the 1.5 amp decoder limit. Remember the stall voltage on a loco can be significantly higher than the normal running voltage. Although your P2K locos combined run well under the 1.5 amp limit, I'm not sure they wouldn't exceed the stall voltage.

I believe stall voltage is measured when a running locomotive is made to stall --- holding it down with your hand will do it. When Model Railroader publishes product reviews, they list the stall voltage. You may find what your looking for in an old review.

[Anonymous]

I installed an MRC AD370 sound decoder in a Proto 2000 FEC E6 diesel. My club uses a Digitrax system, but we couldn't program the decoder to take the Loco's cab number, 1003. When acquired as N0. 03 (factory default), the loco ran and the Sound worked, but bell and light worked only occasionally after much fiddling with buttons on the radio control handheld.

Next, we tried to set up the decoder on a member's NCE system. Initially, the decoder failed to accept the engine number (1003), but then it "took" on the second try. However, the loco would not run at all!

Two other club members are having similar programming problems with MRC decoders. We would all appreciate having definitive answers as to what's wrong.

H. Bell, Tampa Bay MMR Club

[ndbprr]

I've also read that when one unit has lights and the other does not it can affect the speeds.

[cacole]

I'm not familiar with the newer MRC sound decoder, but their early decoders would not accept address numbers above 15, because that was the highest address the MRC DCC system could use. If you have the decoder's documentation, read through it to see if it will accept 4-digit addressing; if not, then you have to keep the locomotive's address at 99 or lower. I tried to program an MRC decoder with an Easy DCC system to a locomotive's address of 449, and even though the programming track reported back that the address had been accepted, it hadn't and the decoder was still on address 3. After several tries, I realized that I was dealing with a 2-digit address decoder and had to use only the last two digits of the locomotive number, 49. The first batch of MRC decoders I bought when they first came out had a failure rate of 3 out of 4.