Tsunami decoder fails with motor wired - Athearn F7

Model Railroader Electronics and DCC
1

What I have tried -

  • Pulled motor and it runs fine on bench with DC supply.

  • Installed Tsunami decoder into engine without motor installed and it programs fine on the track.

  • Wired in motor but insolated motor outside the engine. Now I cannot program or talk to the decoder.

I might have expected this if the motor was fully installed due to some kind of short however with the motor outside the engine and fully electrically isolated, I don’t know what is causing the problem.

Any thoughts?

2

This one has me puzzled. Normally, a decoder can’t be programmed if the motor is not wired in correctly. That’s one reason we always put an engine on the programming track first. Programming uses very little power so it won’t burn out an improperly wired decoder.

How old is this engine? Very old Athearns drew a lot of current, too much for many modern decoders.

What DCC system are you using?

3

How much current does the motor draw, especially with shaft held stopped?

Tsunami are rated at one amp including current for lights.

Rich

4

Sorry about the delayed response, I have been working on a lot of models and 3 GP35s I bought this past month. Sidenote the GP35 is missing a number board, but due to me buying outside of MTH, there’s no warranty. Is there any place that sells number boards?

I forgot to mention last time that I have 2 F7’s, both with the same sound decoder. The 1st one works fine and they both worked well on DC when I tested them initially (before the switch to DCC). The 2nd one as I previously noted is the one that is causing me issues. I ran into someone at a model train store who thought it could be a bad motor, but considering it ran fine on DC, I don’t know what it could be. Tomorrow I’ll try some of the things you 2 suggested and get back to you, much faster this time. I use NCE PowerCab for DCC, and I think I’ll try resetting the decoder without the motor attached, and hopefully things work.

5

Test the motor current on DC, particularly if you grab the shaft and stall it. Also measure the resistence across each segment of the commutator, there could be one winding shorted or partially shorted which will show up as a much lower resistance than the other segments.

As for programming with no motoor - some sound decoders don;t use the motor to generate the ack pulse load, and even if it does - this is just the ack pulse. You can still blind program, as you would with a system that doesn’t have readback. Without the motor connected, you would not be able to read back, even if your system can, if the decoder uses the motor for the ack pulses.

–Randy

6

Other than what has been suggested, cannot comment right now.

I use the Tsunami decoders and Power Cab.

I have used the resistor trick for a Tsunami Micro in a dual decoder set up.

Using a Tsunami as a sound-only decoder

Many folks decide to use these fine sound decoders for their sound generating capabilities and, perhaps, lighting effects. Here are some suggestions:

  • Motor - If you put a 100 ohm 1/2 watt resistor between the gray and orange motor wires or contacts, you can then get acknowledgments back when you program.
  • If you set the Tsunami for Speed Table operation with the USER SPEED TABLE selected and set all speed steps to zero, then you won’t be using your DCC power to heat up the resistor when you are running! To do this, read CV 29 and add 16 to that value and write the result back into CV 29. Then set CV25 = 16 and set all the CVs from CV 68 through CV 94 to zero.

Rich

7

Is this a Genesis or non-Genesis Athearn F7?

Tom

8

What equipment are you using to program it? NCE, Digitrax? Which model command set? Do you have a programming booster?