A quick synopsis for those who have not seen this on other threads.
CB&Q Mikado arrives after months of waiting. Fails out of the box due to a short that occurs when the draw bar is between the locomotive and tender. I call BLI who have me ship it back for inspection.
2 Weeks later and I get my CB&Q box back but with a working undecorated unit. I’m not happy and call BLI. No problem, they will send me a replacement Q model, but they are out and I have to wait until the next production run. I can use the undec in the mean time.
Just last month the Q unit is shipped and BLI arrange for the undec to be collected at their cost by UPS.
Q unit arrives and fails for the same short at the draw bar. I call BLI and they suggest that is is probably a simple short from the underside of the sound board onto the back of the speaker. It isn’t. The short persisted even with the sound system and decoder removed from the tender. A quick probe with my trusty track integrity beeper reveals that the tender chassis is connected to rail A and the locomotive chassis is connected to rail B. A recipe for disaster. I then noticed that the trucks are connected to the pick up terminals inside the tender and that they are supposed to be isolated from the tender chassis by a small plastic filler piece. The rail A truck screw was over tightened and touching metal. A quick adjustment and the short is gone. It is very easy to see how a short could occur over time at this location. In my view a bit of a design error. Anyway, BLI have been nothing but responsive to trying to solve the problem. They were quite willing to ship another unit, but in consultation with the tech support person I decide to try and figure out the problem myself.