Decoder Fail

[John]

I've managed to blow up a few decoders over the years, but never like this ..

DN163K0 in a C40-8 .. motor runs great in one direction, nothing in the other.  Voltage 8V in one direction, and 0V across the motor tabs in the other direction..  Factory reset .. same effect ..

[MK]

Sounds like a manufacturing defect of some sort because if you've fried the decoder it should not work in either direction.

[CNR5529]

This same thing happened to a qsi sound decoder in a walthers y3a a little while back. The motor only worked in one direction, while all other functions remained normal. Half of the motor control electronics were found to be fried. See here:

https://www.therailwire.net/forum/index.php?topic=42198.msg530160#msg530160

I believe @peteski is fixing up that loco as we speak.

[jpwisc]

If it is an Atlas unit, it may be that the motor contacts are coming loose as the motor torques. Try soldering the motor tabs to the bottom of the decoder. This fixed the issue on a couple that plagued me the way you are talking about.

[John]

Sounds like a manufacturing defect of some sort because if you've fried the decoder it should not work in either direction.

Yea .. agree .. I guess I'll send it back to DIGI .. funny thing .. all the lights work etc .. it programs fine as well

[John]

If it is an Atlas unit, it may be that the motor contacts are coming loose as the motor torques. Try soldering the motor tabs to the bottom of the decoder. This fixed the issue on a couple that plagued me the way you are talking about.

I measured the voltages .. and get 0V in one direction at the contact pad .. and 8V in the other direction ..

[peteski]

This same thing happened to a qsi sound decoder in a walthers y3a a little while back. The motor only worked in one direction, while all other functions remained normal. Half of the motor control electronics were found to be fried. See here:

https://www.therailwire.net/forum/index.php?topic=42198.msg530160#msg530160

I believe @peteski is fixing up that loco as we speak.

Yes, it is fixed. One of the H-bridge (motor driver) transistor pairs was fried. I replaced it and that fixed the problem.  This sounds like a similar problem.