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Author Topic: G scale three truck Shay  (Read 1530 times)
The Scotsman

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« on: October 20, 2016, 01:59:49 PM »

I am working on a G scale three truck Shay. I have power from the rails to the small circuit board mounted on the rear of the cab, no voltage to  any of the motors measured at the circuit board. the front light, rear light and the wee firebox light all work. running on straight power no DCC. Does anyone have any ideas or know where I can find an actual schematic not a line drawing of wiring connections ? any help would be greatly appreciated. I don't know if these three motors can run independently or all have to work together for the machine to run.
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Hunt
?
MBB


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« Reply #1 on: October 20, 2016, 02:19:51 PM »

Click Here The PDF contains the only wiring information provided by Bachmann.

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Loco Bill Canelos

Model railroading since 1947


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« Reply #2 on: October 20, 2016, 04:57:58 PM »

Scotsman,

In DC the power pickups on all three trucks go to the main circuit board. When operating properly and when the voltage is increased power goes to all three trucks and they operate together.

The motors definitely do not run independently.

I am sure you have a good power supply, but be sure to apply a fair amount of voltage, as sometimes the motors can be a bit sticky until they finally start.  On one of mine I had to advance the throttle to almost two thirds to get it to move.

Best of luck getting it going.

Loco Bill
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Loco Bill,  Roundhouse Foreman
Colorado & Kansas Railway Missouri Western Railway
Semi Official Historian; Bachmann Large Scale
There are no dumb or stupid questions, just questions!
The Scotsman

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« Reply #3 on: October 20, 2016, 06:16:44 PM »

Thanks to both of you, I do have the PDF but it's no help as to whats happening on the circuit board. The DC power from the track is reaching the board at all three sets of terminals identified for each gearbox, however it's not making it's way from there to the designated terminals to drive the motors. since it's affecting all three motors I'm thinking an open on the board somewhere or a short. I think my next step should be to isolated all three motors and see if the voltage reads differently at the board, and then one at a time throw voltage directly on the wiring leading to the motors and see what happens. I did try ramping up my Bridgewerks controller as you recommended Bill, but it had no affect. Anyway  thank you both for your kind assistance.
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The Scotsman

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« Reply #4 on: October 21, 2016, 11:41:52 AM »

Isolated  all three motors from the circuit board, and one at a time put power directly on the leads leaving the board to the motors, all three motors ran. I'm still thinking something on the circuit board is bad, anyone have any further ideas to isolate the problem?
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Loco Bill Canelos

Model railroading since 1947


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« Reply #5 on: October 21, 2016, 12:45:50 PM »

It would certainly agree the problem is with the main board,  I can't remember for sure but I seem to recall there is one  six prong plug on the main board.  Not sure what it is for and  I am searching in the dark here, but is it possible that the plug connection is loose??  Couldn't hurt to check it.

One possible additional check would be to jump wire the track pickup leads on the main board to the motor leads on the board. This would confirm the board is the problem.  If the motors run then you can be absolutely sure the problem is with that part of the board which passes the voltage to the motor leads.  In a pinch, since the lighting circuits are working, it may be possible to permanently bypass the board motor circuit entirely by using the jumpers.   

Unfortunately I have no other ideas, it is unlikely the 8 prong plug in the tender is the problem as it would affect only that motor and the light in the tender would not work.

Anyone else have some ideas please chime in and give Scotsman some better ideas than mine.
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Loco Bill,  Roundhouse Foreman
Colorado & Kansas Railway Missouri Western Railway
Semi Official Historian; Bachmann Large Scale
There are no dumb or stupid questions, just questions!
The Scotsman

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« Reply #6 on: October 21, 2016, 06:57:15 PM »

Bill, thank you for your help, I found the issue when I lifted the circuit board there was a run (or Lay) whichever you prefer that was burned open, I cut part of it off since it was flopping around and soldered in a jumper straight pin to pin, and it works. Thanks so much for your interest in helping a newbee like myself, it's greatly appreciated. Happy Railroading.   P.S. a wee bit of wire is a whole lot cheaper than a new circuit board.  The Scotsman.
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JerryB

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« Reply #7 on: October 21, 2016, 08:30:47 PM »

Glad you found it!

The technical term for the conductors on a circuit board is "trace." Finding an open like you describe most likely means the board was subjected to a direct short of the motor outputs.

Since it now works, it seems that none of the solid-state components (output transistors) were harmed.
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Sequoia Pacific RR in 1:20 / 70.6mm
Boonville Light & Power Co. in 1:20 / 45mm
Navarro Engineering & Construction Co. in 1:20 / 32mm
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Loco Bill Canelos

Model railroading since 1947


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« Reply #8 on: October 21, 2016, 10:45:44 PM »

That is great news, glad you found the problem.  I have seen this kind of short when one of the trucks derails, but most I have seen were not on the main board but one of the contacts on one of the trucks.  the main board must have had a big jolt!  Any fix that works is a good one!! 

Have fun with it.

Bill
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Loco Bill,  Roundhouse Foreman
Colorado & Kansas Railway Missouri Western Railway
Semi Official Historian; Bachmann Large Scale
There are no dumb or stupid questions, just questions!
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