The Randall Museum in San Francisco hosts a large HO-scale model model railroad. Created by the Golden Gate Model Railroad Club starting in 1961, the layout was donated to the Museum in 2015. Since then I have started automatizing trains running on the layout. I am also the model railroad maintainer. This blog describes various updates on the Randall project and I maintain a separate blog for all my electronics not directly related to Randall.
2023-09-09 - UP 8330 is Working Again
Category RandallThe little saga with the new Walthers Mainline SD70ACe continues for UP 8330: The engine had stopped working a few months ago, and it’s now working thanks to the excellent support from Walthers. I really appreciate how they stand behind their product -- seriously.
The issue here seems to be solely with the ESU new “Essential Sound Unit” decoder: all I had to do was provide a picture of the failed decoder, let my support contact identify the issue, and they sent me a replacement decoder. This avoided me having to send the entire engine, although that would have been an option (not everyone is going to be comfortable opening their engine and changing the 21-pin decoder, and that’s fine). Support as I like it: cordial, competent, fast, and flexible. “Walthers A++” seriously on that one.
Here’s a comparison of the decoders:
Left: defective decoder. Right: new decoder. Can you spot the difference?
In that case, there’s a tiny 22 Ω (code 220) surface-mount resistor (just below the “E.S.U.” stencil on the board). In the failed decoder, it is charred and has obviously overheated. It is pristine in the new decoder. I do remember pointing out in my initial issue page that the hood of the engine was hot when the decoder first stopped working. Coincidence? I don’t think so.
In between I had been chatting with another user via YouTube and they had a failure on a similar engine with the same decoder, and the cause was the same. That points to a defect on the decoder board.
I shall also point out that opening the engine to change the decoder is a fairly simple process. I’ve documented the shell removal here: Shell Removal: HO Walthers Mainline SD70ACe
One does need to be careful when removing the decoder from the 21-pin socket. That’s not unique to this decoder, but the same for all 21-pin decoders: one needs to carefully lift it from both front and back sides, using a small plastic tool like pliers for leverage. The problem is that it’s very easy to bend the pins if the decoder is not level when removed.
Same goes for putting back the decoder. One of the pins is purposely missing, which matches a corresponding key slot on the decoder board. This ensures proper orientation of the decoder. It should fit easily without having to force.