I installed a DH123AT decoder some time ago in an Athearn AC4400. It didn't have the DCC plug so this kit came with a replacement board. I installed it with no problem and it worked well at the time.
Some months ago I was doing some speed matching (or trying to LOL) and played around with some CV's. Then I got sidetracked for a few weeks. I have just recently come back to this loco and it runs but I can't get it to a reasonable top speed. It just crawls in forward and reverse. I have tried resetting CV8 back to factory setting 08 and still the same problem. The lights work fine. I then tested it on DC and it ran fine and it did get to top speed, so the loco motor seems to be OK.
I have a Zephyr. All my other DCC equipped locos seem to work fine. Is there a particular CV , or CV's I should change? If I recall I did change some of the CV's like 03, 05, 06 but that didn't seem to change anything, so I reset to factory.
I'm wondering if the decoder is defective. How can I confirm this?
Any help would be appreciated.
Tom
Possibly the decoder didn't reset. But if you're looking for something to try:
CV3 is the acceleration rate adjustment. If you set this value too high, the engine will get to full speed, but it might take awhile to get there. If I understand the Digitrax decoder manual this CV has a range of 0 to 31. So you can reset this CV to 0 and see what happens.
CV 5 sets the maximum voltage going to the motor and has a range of 0 to 255. A value of 255 gets you 100% of the voltage at top speed. So you'd want to set this CV to 255.
Concerning CV 6, this is the mid-voltage adjustment. According to the Digitrax manual there is an interaction between this CV and CV 2, which is the starting voltage. So that I don't confuse anything, he is what the manual says:
6.7 V-mid: CV06
Setting CV06, V-mid or mid point voltage specifies an exact voltage that is
applied to the motor at speed step 15 ( or speed step 7 in a 14 step system). The
range of available V-mid CV values is from 000/x00 to 255/xFF. A value of
128 applies 50% of the total voltage to the motor at step 15 (28 speed system).
A value of 255 applies 100% voltage at the middle speed step.
If V-start (CV02) is accidentally programmed to a CV value greater than that
programmed for V-mid (CV06), the decoder will force the output voltage for
all steps below the V-mid value to be fixed at the V-mid value. This is done to
prevent undesirable operational effects.
37
If a value of 00 or 01 is programmed into CV06 (V-mid), the decoder assumes
a "straight-line" throttle response curve is desired. In this case, the decoder will
run as though V-mid were set at a value of 50% of total motor voltage.
Note: Some Digitrax decoders are not able to set V-mid in 128 speed step
mode. If you encounter this problem, status edit the decoder to run in 28 speed
step mode and you will be able to set up v-mid.
V-mid is not available when loadable speed tables are in use.
Good luck (no, I'm saying that, not the manual)
Thanks. I did read the manual and tried just about everything. Still no change. Let me experiment a bit more.
Ballantrae Road I'm wondering if the decoder is defective. How can I confirm this?
The only way to know for sure is to replace it with another decoder, or remove it and use a decoder tester if you have one.
You can also try setting CV's 55, 56, and 57 to zero.