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Repairing a Murphy Models B141 circuit board fault

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One of my Murphy Models 141s developed a mysterious fault which I tracked down to a dry joint between the Bachmann Circuit Board and 21 Pin Decoder interface. 

The locos is pretty much a 'shelf queen' in a display case and has seldom run since purchased when the locos were originally released.

The loco failed to respond to the controller in any way shape or form which pretty much isolated the fault to the circuit between the wheel pick ups and relevant pins on the 21 pin plug.

The biggest challenge was finding a reference to the decoder interface that provided a clear illustration of the pin out layout 21 & 22 in the case of track power.

1874997551_NMRA21MTCPinout.JPG.80bd4a0461241fcaac77ec0f73e65c56.JPG

It was a simple exercise with a continuity tester to detect the fault which turned out to be a dry soldered joint between the board and in this case pin 22

 

1661246489_MM141circuitboard.jpg.6188b95f3f38e6feb4cc1b63a87b1d2a.jpg

On inspection it looked like the solder had not penetrated fully around Pins 21 & 22 during the surface mounting process.

I re-soldered Pin 22 with a fine tipped soldering iron and a dot of multi-core solder

2033811065_MMcircuitboard2.jpg.a4478bd7a962539d793fa29b7ea5b027.jpg

The repair seems to have done the job, it will be interesting to see if a similar problem develops with pin 21.

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Very informative, thanks for sharing.

I bought a 141 from Ebay a few years back. I got it really cheap as it was sold as a non-runner. 

Turns out it had a similar-but-different issue with the PCB, the track feeds at one end of the board had failed. I had to rewire to the opposite end of the board and all was fine after that. 

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On 26/12/2020 at 11:31 PM, Mayner said:

One of my Murphy Models 141s developed a mysterious fault which I tracked down to a dry joint between the Bachmann Circuit Board and 21 Pin Decoder interface. 

The locos is pretty much a 'shelf queen' in a display case and has seldom run since purchased when the locos were originally released.

The loco failed to respond to the controller in any way shape or form which pretty much isolated the fault to the circuit between the wheel pick ups and relevant pins on the 21 pin plug.

The biggest challenge was finding a reference to the decoder interface that provided a clear illustration of the pin out layout 21 & 22 in the case of track power.

1874997551_NMRA21MTCPinout.JPG.80bd4a0461241fcaac77ec0f73e65c56.JPG

It was a simple exercise with a continuity tester to detect the fault which turned out to be a dry soldered joint between the board and in this case pin 22

 

1661246489_MM141circuitboard.jpg.6188b95f3f38e6feb4cc1b63a87b1d2a.jpg

On inspection it looked like the solder had not penetrated fully around Pins 21 & 22 during the surface mounting process.

I re-soldered Pin 22 with a fine tipped soldering iron and a dot of multi-core solder

2033811065_MMcircuitboard2.jpg.a4478bd7a962539d793fa29b7ea5b027.jpg

The repair seems to have done the job, it will be interesting to see if a similar problem develops with pin 21.

That looks like the baby GM is sitting on scale 21mm gauge track. Any other photos of the model on 5'3" scale track?

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