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Discussion Starter · #1 ·
Inherited a number of loco's from my late uncle. Having trouble getting them to run correctly, in particular two USA Train SD40-2's. The one I am working on now had bad shoes and idler shafts. All were replaced, old grease cleaned, and re-assembled.

Smoke and sound work correctly. All pickups, wheel and shoes, have good power. Engine (on test rollers and upside down in repair cradle) runs fine in reverse with a total draw of about 3.5 amps @ 19 volts. When I try to run forward there are two issues: 1.) Sound comes on, but the drive wheels still run in reverse. 2.) Amperage draw quickly climbs past 10 amps and test track safety fuse blows.

Using my Kadee brass wheel brush I have individually tested the six pickup points - wheels and shoes- independently and the results are the same.

My other issue is trying to remove the rear half of the cab. Took out every screw I could find, still felt like the cab was glued to the frame.

Any help would be greatly appreciated.
 

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Super Modulator
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3.5 amps unload is WAY too much current, you have something wrong. Disconnect the motor blocks and remove them from the loco. Jumper the 2 outer pins (that jumpers motor to track)... test them individually that way.

Look carefully under the motor blocks, often hidden screws.

look here: several pictures where you can see all the screw holes (picture with shell off) (sometimes assembled while paint not cured, will feel like glue)


Greg
 

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Discussion Starter · #3 ·
Inherited a number of loco's from my late uncle. Having trouble getting them to run correctly, in particular two USA Train SD40-2's. The one I am working on now had bad shoes and idler shafts. All were replaced, old grease cleaned, and re-assembled.

Smoke and sound work correctly. All pickups, wheel and shoes, have good power. Engine (on test rollers and upside down in repair cradle) runs fine in reverse with a total draw of about 3.5 amps @ 19 volts. When I try to run forward there are two issues: 1.) Sound comes on, but the drive wheels still run in reverse. 2.) Amperage draw quickly climbs past 10 amps and test track safety fuse blows.

Using my Kadee brass wheel brush I have individually tested the six pickup points - wheels and shoes- independently and the results are the same.

My other issue is trying to remove the rear half of the cab. Took out every screw I could find, still felt like the cab was glued to the frame.

Any help would be greatly appreciated.
 

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Discussion Starter · #4 ·
Greg, thanks for the reply. Rechecked, my bad typing..... 2.035 amps in reverse & in forward builds to10 amps in about 8 second (not a short but a steady climb).

Finally found all the hidden screws and removed the shell. It's always interesting what some folks will do under the hood. It appears my uncle was experimenting with two different Digital control setups. There were two SD40-2's in the boxes my aunt sent. One is definitely setup with a GWire by NCE. I got the second Loco to run with that system - bell horn- and drive, but it runs very slow.

This Loco seemed to run on analog (my layout is 100% analog) so I was getting it ready for sale when I noticed 2 wheel sets were not turning. Replaced all six intermediate gear sets, greased, replaced shoes and put on the test stand.

Under the hood I now see boards and wiring have been modified and added. In uncle's box-o-stuff there were both NCE Gwire and an Aristocraft AR5473 Digital Systems.

Since SD40-2 that is tied to the NCE system did not even have the rails yet installed. I have no way of knowing if my uncle was changing over and had not yet put it in service. He had an extensive garden railway, but due to illness he quit the hobby about 6 years ago.

Might think about packaging the NCE Gwire, (2) USA SD40-2's, & Aristocraft System and just Ebay'ing them all.
 

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Super Modulator
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OK, lots of stuff here...

Now that you have it open, easy to isolate the motor blocks and test individually. Get them disconnected from the other electronics.

On the motor blocks, if the intermediate gears were worn, you need to check for the dreaded split axle problem:

Interesting mix of the Gwire and the Aristo system.

Let us know how you go, the Gwire should have separate receivers, and is not compatible with the Aristo, so maybe a picture would be needed if you need help.

Greg
 

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Discussion Starter · #6 ·
OK, lots of stuff here...

Now that you have it open, easy to isolate the motor blocks and test individually. Get them disconnected from the other electronics.

On the motor blocks, if the intermediate gears were worn, you need to check for the dreaded split axle problem:

Interesting mix of the Gwire and the Aristo system.

Let us know how you go, the Gwire should have separate receivers, and is not compatible with the Aristo, so maybe a picture would be needed if you need help.

Greg
I have looked around for a wiring schematic for the SD40 and have come up empty. Does one exist? It would help trying to get this thing back to stock.
 

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Discussion Starter · #7 ·
Greg,

I have looked around for a wiring schematic for the SD40 and have come up empty. Does one exist? It would help trying to get this thing back to stock.

Please excuse my posting ignorance, this is my first forum. Thanks for all your help. I will do more testing tomorrow night.

mike
 

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Super Modulator
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You are doing just fine!

There are not a lot of wiring diagrams for the USAT locos.

If it has the stock boards, it's not too hard to figure out, but some pix will help.

The trucks plug into the main board. There is a separate board to regulate the power for the smoke units. Usually a 3 pin plug on the main board powers headlights and cab lights.

Greg
 

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Discussion Starter · #9 ·
Made some progress. With Loco on test stand, during testing the sound comes on and the speed increases like momentum is programmed into the Loco:

1.) Unplugged the REAR trucks. Ran in REVERSE (wheels turned CW), 19.4 volts & 1.01 amps. Switched polarity to run Forward (wheels still turned CW), wheels started to turn and the amperage was quickly building, shut it down at 10 amps. Sound was on.

Next, unplugged the FRONT trucks. Ran in REVERSE (wheels turned CW), 19.3 volts & 1.07 amps. Switched polarity to run Forward (wheels still turned CW), Ran fine. 19.2 volts & 1.09 amps.

I did check all the diodes on the board for shorts / open. They were not tested out of circuit, but got reasonable readings forward and back - .564 / 1.40.


No reversing puzzles me unless it has to do with the DCC that was installed. I have included pictures.

Mike
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Super Modulator
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You have a standard QSI Revolution decoder and the optional AirWire/Gwire receiver.

The decoder will take commands only from the GWire throttle as long as the flex cable is plugged in.

Unplugging it will allow standard track power DCC. As it sits, looks like set up for track power.

It will run from anything on the track, DC or DCC as power.

I know a fair deal about this stuff. I use a lot of QSI decoders.


Greg
 

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Discussion Starter · #11 ·
You have a standard QSI Revolution decoder and the optional AirWire/Gwire receiver.

The decoder will take commands only from the GWire throttle as long as the flex cable is plugged in.

Unplugging it will allow standard track power DCC. As it sits, looks like set up for track power.

It will run from anything on the track, DC or DCC as power.

I know a fair deal about this stuff. I use a lot of QSI decoders.


Greg
Thank you for the help.

My G Scale layout - 28 x 30 mostly LGB is indoors and all Analog, never had the need to dabble in digital control.

Any thoughts why I have only reverse and no forward? Switching the power polarity makes no difference.
 

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Super Modulator
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1.) Unplugged the REAR trucks. Ran in REVERSE (wheels turned CW), 19.4 volts & 1.01 amps. Switched polarity to run Forward (wheels still turned CW), wheels started to turn and the amperage was quickly building, shut it down at 10 amps. Sound was on.

so the rear trucks are unplugged and you are trying to use the electronics to run the front truck?
still a bit confused, lets start here with how were you powering the truck, I want you to disconnect a truck and run it directly from DC power.


Next, unplugged the FRONT trucks. Ran in REVERSE (wheels turned CW), 19.3 volts & 1.07 amps. Switched polarity to run Forward (wheels still turned CW), Ran fine. 19.2 volts & 1.09 amps.
 

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Discussion Starter · #13 ·
1.) Unplugged the REAR trucks. Ran in REVERSE (wheels turned CW), 19.4 volts & 1.01 amps. Switched polarity to run Forward (wheels still turned CW), wheels started to turn and the amperage was quickly building, shut it down at 10 amps. Sound was on.

so the rear trucks are unplugged and you are trying to use the electronics to run the front truck?
still a bit confused, lets start here with how were you powering the truck, I want you to disconnect a truck and run it directly from DC power.


Next, unplugged the FRONT trucks. Ran in REVERSE (wheels turned CW), 19.3 volts & 1.07 amps. Switched polarity to run Forward (wheels still turned CW), Ran fine. 19.2 volts & 1.09 amps.
I unplugged both the front and rear trucks. Put power to one set at a time via pin patch cables (picture attached). 19.4 volts about 1.0 amps. Trucks run in forward and reverse correctly, both front and rear. The issue appears to be in the add-on electronics. I wish I had at least a picture of what the stock setup looked like. I would be happy just to get it back to an analog, correctly working loco.
 

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So probably either miswiring or blown output transistor on the qsi.

If it was me, I would bypass the QSI decoder and wire the motors and the track pickups back to the original board.

(you can have a blown output transistor in the decoder that only affects one direction)

The main board has markings for motor and track, might be able to help if you get a picture of that board from above with the wires pulled to the side...

Greg
 

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Discussion Starter · #16 ·
Attached is a clear view of the circuit board. It looks straight forward, I can see the following connections:

MOTOR 1
MOTOR 2
PICK 1

I can't read the circuit board with the boogered up soldered wires. PICK 2 as a guess?

The sound plug gets moved from the decoder to the upper right corner connector? The pin description on the board is covered by the male socket, all I can see is "s_____1", and I can see a sound 2 that was never soldered.
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Mike,

If you are just interested in restoring your SD40-2 loco to its original factory wired connections, I had occasion to do this with a used loco I had purchased. (A few posts back Greg E. had provided a link to my "vignette" (article) that includes doing just that.)

Illustrated below is how I had received my Union Pacific SD40-2



Note that the "PICK2" color code wires on the switch board (shown above) were reversed on my SD40-2 like they are in your picture!

Within the "vignette", take a look at section concerning the switch board as this may be of help. (I corrected the PICK2 wires and also had to make new cables with appropriate connectors because they had been cut off and missing from the switch board.)
Click on "USA Trains SD40-2 Experiences - Switch Board and Cables"
(You will, also, see how the trucks are wired.)

I did make one difference with respect to the factory truck wiring connections to improve serviceability - shown and described below.



-Ted
 
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