Model Train Forum banner

1 - 20 of 27 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter #1
I have this Atlas S-4 Model #8285 (PENNSYLVANIA Rd #8431) that I have been trying to install a DH126D decoder in... I soldered in a 9-pin plug, as per instructions (isolated motor)/ orange & gray to motor/// black & red to wheel pickups /// blue & white to front light (diode w/resistor).... It ran nice, so I installed my sound decode, two wires, to the wheel pickups, sounded good. Came back the next day "fired-up" the engine, SHORT warning came on. Checked wiring and everything else with ohm meter, no shorts I could find, but now I have no motor functions, light and sound still worked. put decoder in another engine no motor function-KAPUT!! Put in new plug & new decode...KAPUT!! Removed 9-pin plug and sound, then installed a Bachmann 44913 decoder (hard-wired)... Now as soon as I enter decoder address, motor bumps on for a turn, then system goes to SHORT... ANY ONE KNOW WANT IS GOING ON!!!!!!!!!!!
 

·
Registered
Joined
·
690 Posts
HD, could u isolate the motor leads and check it separately? The system is continuously saying SHORT, maybe it's true...possibly something in the brushes or something shorting the wiring when u replace the shell??
It was not DCC ready to start with, correct?
The light board is gone, correct?
 

·
Registered
Joined
·
690 Posts
"Absolutely the first thing you should do is measure the
'stall' current. These old locos pull down a lot. I just
fried a decoder with an old Mehano. Now I measure and I didn't
even get to the 'stall', just running on it's side it was drawing
1.5 to 1.7 amps.
You may need to replace the motor or go to a decoder that
can handle the high amps.
Don "

HD, this was from a 2015 post. If your loco is newer, prolly no issue.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #4
"Absolutely the first thing you should do is measure the
'stall' current. These old locos pull down a lot. I just
fried a decoder with an old Mehano. Now I measure and I didn't
even get to the 'stall', just running on it's side it was drawing
1.5 to 1.7 amps.
You may need to replace the motor or go to a decoder that
can handle the high amps.
Don "

HD, this was from a 2015 post. If your loco is newer, prolly no issue.
How do you check "stall" current?
 

·
Registered
Joined
·
8,518 Posts
You state that replacement decoder responded with the
normal 'motor jerk', then your DCC controller went to SHORT.

Usually, if you get a DCC controller showing 'Short' the
problem is on the track side of the Decoder. A short on
the 'output' (motor-light) side of the decoder would damage the device.
A motor drawing too much current would destroy the
decoder but unlikely to cause a 'short' indication on the
Controller. (but it could depending on what 'burned'
inside the decoder.)

If you isolated the motor from the frame and made
certain no wires from the decoder touch the frame
or each other then it would be my guess that something
is amiss in the red/black wires from the trucks to the
decoder. Did you try disconnecting the sound decoder?

Use your multimeter set to ohms, remove the loco
from the track, touch one probe to the left pickup wheel
and the other probe to the right. Do you still get a
'short' indication?

Another thought...if the Controller 'short' indication goes away when
you remove the loco from the track, do any of your other
DCC locos then operate normally? If not, you may have
a Controller problem or a problem in wiring from Controller
to the track or some stray metal is touching both rails. To
narrow the possibilities, remove one of your other previously
working locos from the track, disconnect the track from
the Controller, touch wires from the decoder to the wheels
of the loco...does it still function normally? If so there is
a problem in track or track wiring...if not there is a problem
with the Controller. Does it have a 'short sensitivity' adjustment?

Don
 

·
Registered
Joined
·
47 Posts
Discussion Starter #8
Checked out the "stall" current... 1.5-amps, a little high for 1-amp decoders. Looks like time to upgrade...
 

·
Registered
Joined
·
47 Posts
Discussion Starter #10
You state that replacement decoder responded with the
normal 'motor jerk', then your DCC controller went to SHORT.

Usually, if you get a DCC controller showing 'Short' the
problem is on the track side of the Decoder. A short on
the 'output' (motor-light) side of the decoder would damage the device.
A motor drawing too much current would destroy the
decoder but unlikely to cause a 'short' indication on the
Controller. (but it could depending on what 'burned'
inside the decoder.)

If you isolated the motor from the frame and made
certain no wires from the decoder touch the frame
or each other then it would be my guess that something
is amiss in the red/black wires from the trucks to the
decoder. Did you try disconnecting the sound decoder?

Use your multimeter set to ohms, remove the loco
from the track, touch one probe to the left pickup wheel
and the other probe to the right. Do you still get a
'short' indication?

Another thought...if the Controller 'short' indication goes away when
you remove the loco from the track, do any of your other
DCC locos then operate normally? If not, you may have
a Controller problem or a problem in wiring from Controller
to the track or some stray metal is touching both rails. To
narrow the possibilities, remove one of your other previously
working locos from the track, disconnect the track from
the Controller, touch wires from the decoder to the wheels
of the loco...does it still function normally? If so there is
a problem in track or track wiring...if not there is a problem
with the Controller. Does it have a 'short sensitivity' adjustment?

Don
I isolated motor...nothing touching to cause short... sound decoder was removed.., no short red-black or anything else... no short rt. wheel - lf. wheel or to anything else... Omh reading across motor was 12-11.7 Ohms.... with engine on track ,ohm reading was 9.6... Other DCC engine function fine on same track... NEW DEVELOPMENT... WITH "GOOD" ENGINE ON TRACK IN IDLE, SET S-4 ON SAME TRACK AND SHORTED RIGHT AWAY!!??!!
 

·
Registered
Joined
·
8,518 Posts
Since 'good' engine functions correctly, that would seem to
indicate that the DCC controller is not a problem.

Is it possible that you did a 180 on one of the trucks? If red wire is on
'right' rail wheels on front truck, it is also on 'right rail' wheels on rear truck?
Are the two red wires tied together inside at input to decoder? Same with black wires.

Have you tried loco on it's side, probes, connected to track feed, touching left and
right truck wheels? Does it still short the controller?
If so, we're pretty much down to the appearance of a shorted
decoder input. A final test would require you to remove
the decoder from the loco. Probe the input wires with
track voltage. If it still shows short, it has been damaged.
Digitrax and NCE both have excellent warranty
policies...they require you to contact them, describe problem, and
they'll replace your defective decoder even if you personally
damaged it. You will need paid receipt.

Don
 

·
Registered
Joined
·
2,078 Posts
So if you disconnect the decoder, then set the loco on the track does it short? That would at least isolate between plug and loc wiring, or Decoder problems. While you have the decoder unplugged, check the isolation between the chassis and the motor wires, it should be open. Lights should also be isolated from the chassis, especially if the chassis is one side of the rail pickup. I would not do any resistance probing with the decoder in the socket.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #13
Since 'good' engine functions correctly, that would seem to
indicate that the DCC controller is not a problem.

Is it possible that you did a 180 on one of the trucks? If red wire is on
'right' rail wheels on front truck, it is also on 'right rail' wheels on rear truck?
Are the two red wires tied together inside at input to decoder? Same with black wires.

Have you tried loco on it's side, probes, connected to track feed, touching left and
right truck wheels? Does it still short the controller?
If so, we're pretty much down to the appearance of a shorted
decoder input. A final test would require you to remove
the decoder from the loco. Probe the input wires with
track voltage. If it still shows short, it has been damaged.
Digitrax and NCE both have excellent warranty
policies...they require you to contact them, describe problem, and
they'll replace your defective decoder even if you personally
damaged it. You will need paid receipt.

Don
I removed everything... Went back to basic DC, runs great... No crossed wires. (Decoder is hard-wired, when installed, no plug on this one.
 

·
Registered
Joined
·
47 Posts
Discussion Starter #14
Pulled trucks apart, alot of grease/oil... cleaned out excess... all connections good, no shorts in trucks
 

·
Registered
Joined
·
47 Posts
Discussion Starter #15
At this point I can't tell if the decoder is still good, but if I bump the Throttle on, the engine moves about a 1/2 inch before the "short" shuts the system down...
 

·
Registered
Joined
·
690 Posts
I know how frustrating this is, HD... That cradle around the motor, is it metal? It appears inseparable from one side of the motor winding... If so, is it isolated from any part of the frame that could have continuity to the rails? It would behave fine on DC, but not on DCC... Just asking 😊
 

·
Registered
Joined
·
47 Posts
Discussion Starter #18
Its metal, "hot" on the bottom and the red plastic insulates it on the top... I've got black tape under the motor, no contact
 

·
Registered
Joined
·
47 Posts
Discussion Starter #20
Was up till 4am, removed the "board" that I used to solder the motor wires to and put in a DCC ready board from a Bowser AS-16 that I had laying around w/8-pin plug... plugged in a Bachmann decoder and... to be continued...
 
1 - 20 of 27 Posts
Top