Bad Decoder ?

[C_O_Fan]

I have an old Athearn GP-7
and I bought just a simple Digitrax DH 123 AT
decoder thinking I could consist it with one of my GP-9 sound units

This is the type of decoder that comes prewired for Athearn locos
and has no sound
Like this
http://www.digitrax.com/prd_mobdec_dh123at.php

The lights work fine and are bi directional as they should be but the loco won’t run
it just sits there and makes a soft buzzing noise when I turn up the throttle

I unhooked the decoder and tested the motor with a 9 volt battery and it works fine

I checked continuity in between the track and the electrical contacts and everything is fine

I reset the decoder to defaults but the same thing happens

Any thoughts ?

[cmarchan]

Did you remember to isolate the lower motor contact from the frame?

Pardon the next question; did you discard the top power strip? (I’ve seen installs where they did not remove it!)

[C_O_Fan]

Did you remember to isolate the lower motor contact from the frame?

Yes i put down 2 layers of electrical tape

Pardon the next question; did you discard the top power strip? (I’ve seen installs where they did not remove it!)

Discard It ? no i took ot off and put it in my junk box and used the one that came with the decoder

But thanks for asking !

[cmarchan]

If you have a small 12 Volt lamp (50~100ma), you can attach it to the gray and orange wires in lieu of the motor and check it’s brilliance as you increase the throttle; it should vary as the throttle varies.

If that is successful, with a VOM (Volt-Ohm-Meter) you can measure the motor’s stall current. If this is a motor with the older one piece magnet, your motor’s stall may be too high. Set the meter to its highest current setting and place the leads in series with the motor; set the input voltage to 12~14 Volts. Stop the shaft from rotating by hand and note the current draw.

[C_O_Fan]

If you have a small 12 Volt lamp (50~100ma), you can attach it to the gray and orange wires in lieu of the motor and check it’s brilliance as you increase the throttle; it should vary as the throttle varies.

If that is successful, with a VOM (Volt-Ohm-Meter) you can measure the motor’s stall current. If this is a motor with the older one piece magnet, your motor’s stall may be too high. Set the meter to its highest current setting and place the leads in series with the motor; set the input voltage to 12~14 Volts. Stop the shaft from rotating by hand and note the current draw.

I checked the stall current prior to the install and it was just under 0.5 amps

These are Rated at 1,5 to 2.0 amps peak

[cacole]

Here are a couple of other, quite obvious things, to check:

Is the mechanism bound up from removing and replacing the motor? Can you turn the flywheels by hand?

Does the loco run on default address of 3?

If you have tried resetting the decoder address to a four-digit one, try setting CV 29 to a value of 34 as a separate step. You may be trying to run it on the long address, but if you don’t reset CV 29 the decoder still thinks you’re using the default.

[C_O_Fan]

Here are a couple of other, quite obvious things, to check:

Is the mechanism bound up from removing and replacing the motor? Can you turn the flywheels by hand?

Yes it turns freely

Does the loco run on default address of 3?

Don’t know didn’t try it

since I’m using Decoder Pro i can easly reset to default and try it

I used Decoder Pro to set the long address

If you have tried resetting the decoder address to a four-digit one, try setting CV 29 to a value of 34 as a separate step. You may be trying to run it on the long address, but if you don’t reset CV 29 the decoder still thinks you’re using the default.

[cudaken]

Have you try to run it with the shell off? I know that sounds dumb, but I did have a self wired DCC conversion that did not want to run with the shell on due to a platform from the original DC set up was hitting the flywheel. It is a old PK 2000 BL 2.

[C_O_Fan]

Not a bad idea Ken !

But something weird is going on I’ve tried to reset the decoder several times but it’s stuck on the 4 digit address

I’m shipping it back to digitrax

[rrinker]

Not having it wired properly, including having one of those slip-on connectors being loose (the one that connects to the piece of the headlight bracket that is riveted to the frame is a primary culprit, well, actually there it is the rivetn, there’s usualy not great contact between that tab and the frame), will cause it to not run right and also not take programming properly, including a CV8=8 reset.

–Randy

[C_O_Fan]

Not having it wired properly, including having one of those slip-on connectors being loose (the one that connects to the piece of the headlight bracket that is riveted to the frame is a primary culprit, well, actually there it is the rivetn, there’s usualy not great contact between that tab and the frame), will cause it to not run right and also not take programming properly, including a CV8=8 reset.

–Randy

Yeah Randy I know what you mean

I didn’t like the loose fit so I drilled a hole in the frame and tapped it out then filed all the paint off then flattened the clip and drilled a hole in it and used a 2/56 screw to fasten it to the frame for a better contact