Interesting problem DN121.

[Altoona]

Troubleshooting a problem with a DN121. There problem is no response from motor, like its dead
I have check decoder with Loy's Toys decoder tester, all led's respond to to proper function.
I'm able to set engine number and and have it response to new number on tester
I have hook a volt meter to motor leads and getting 13.9 volts output.
I have tried 3 known good motors and still nothing.
I'm using a Digitrax DS51 with a Soundtrax PTB100 booster
 
Does anybody have any suggestion what the problem is and a fix.

Judd Barton
PRRTHS #9210

[peteski]

DN121 (or is it a DZ121?) is really ancient, but it is a (really basic) DCC decoder. There was a known problem with certain run of those, but not what you are experiencing.

Was this decoder previously installed and working in a model locomotive, or you just found is loose and tried to use it?

I'm not  familiar with that decoder tester.  You mention that functions check out ok. Does the tester have a motor which is used for a load during test? Does that motor run?  if not, and the problem is with the motor circuit, then that tester is not very thorough.  You can have decoder where motor circuit is blown, but other functions will still work.

[tehachapifan]

The motor leads from the decoder are putting out that voltage to several known good motors and none of them run? That's a head-scratcher?

Was going to suggest the decoder may be set to a consist address, but I guess that's not it.

[John]

1. I have hook a volt meter to motor leads and getting 13.9 volts output.

Are you getting a constant 13.9 volts even when you turn the trottle down?    Make sure you are measuring between the gray and orange wires

2. I have tried 3 known good motors and still nothing.

Q - Did you try using a 9volt battery across the motor to make sure they run to double check?

Q - Did you install these motors into the locomotive?   If they are in the locomotive, make sure you can apply battery power to the motor to see if they run.

Q - How are you wiring the decoder to the motor?  Soldering?  Does the motor work after you solder to it?

I know these are basic questions -- but trying to rule out some things

[Altoona]

Checked voltage with meter 0.0 to 12.98 to 0.0 volts
Check it again, now have have a dead short.
Check to see if anything was touching, it was clear of anything.
So I believe the decoder is fried but good.
Thanks to all who trier to assist.

Judd Barton
PRRTHS #9210

[peteski]

Checked voltage with meter 0.0 to 12.98 to 0.0 volts
Check it again, now have have a dead short.
Check to see if anything was touching, it was clear of anything.
So I believe the decoder is fried but good.
Thanks to all who trier to assist.

Judd Barton
PRRTHS #9210

You still have not directly answered the questions I and others have asked.
What we tried to do is called analytical troubleshooting, but now that you declared the decoder dead, then it is dead.  No need to provide any additional answers. You might still be able to use it as a function-only decoder (if you even need one).