Heljan Class 128 DPU and fitting a Bachmann 36-557 21pin decoder

[Dr.Glum]

I writing this in case someone else does what I've done and ends up thinking they've fried the chip. The story has a happy ending.

"This should be an easy install", thinks I. Is there such a thing? It's my first time with one of these Next21 chips. Just plug the chip in and program it. Ha! First thing to take the smile off my face was the force needed to remove the blanking plate. Then the force needed to get the chip to sit even half way down the pins. "That's enough for tonight, I'll test and program tomorrow."

Tomorrow comes and it doesn't respond on the programming track. I may or may not have set cv1, so onto the layout and - nothing. Doesn't respond to address 3 or my 87. Lights are off. A test loco responds, so its not that. Hey ho, what have I damaged, I'll put the blanking plate back. Then I am worried because it doesn't work like it had on DC previously.

I trawl through RMweb looking for inspiration, learning several useful things along the way, but no joy. I bought this chip in 2016 so it came in a little cardboard box with a folded up leaflet. I now looked at the leaflet and a diagram labelled "Fitting the decoder". All straight forward, but light dawned when I read underneath about sometimes fitting it the other way up. Had I checked last night which way up? I couldn't remember.

When I put it in as per the sketch, far less force was needed, it worked, and was programmable. So I hadn't buggered anything. Lesson learned: take a photo of the inside of the loco before removing the blanking plate, because today I must also have refitted that upside down as well. Doh!Photo shows almost finished installation. Couple of loose bits to stick back on.