[Accrs-ho] FW: Weird Model RR Problems

[ACCRS HO Scale]

The e-mail below is from Gary Schrader who lives in San Jose and is a name in the local “O” scale circles.  

 

From: gs-sj1944 at comcast.net [mailto:gs-sj1944 at comcast.net] 
Sent: Sunday, June 18, 2017 12:18 PM
To: gs-sj1944 at comcast.net
Subject: Weird Model RR Problems

 

All,

 

I've had several weird problems crop up recently relative to model railroading. Some of you might encounter some of these issues on down the road, so I'm passing them along for your info.

 

Those attending my layout tour on Saturday of O Scale West saw the first problem. While running trains, I suddenly was unable to stop most of the engines from whistling. Only the one I was trying to control had the problem, but every time I changed engines, the new one had the problem. I had never run into this before and assumed I had an overall system problem. A couple of days later I diagnosed the problem. It was no big issue with my NCE radio controlled system at all. It was just the specific ProCAB controller I was using. There was no problem when I changed controllers. Turns out that the batteries had gotten really low on the controller I was using at the time. Putting in new batteries cured the problem. I have run down the batteries in controllers many times without that happening. Usually, you start having problems getting commands sent. This was a newer controller I had not used much, so it was probably the first time I had run down its batteries. So here's the first tip:

 

If you suddenly cannot stop your engine from whistling when using an NCE ProCAB controller. Check for low batteries.

 

The second problem arose when a gentleman in Seattle could not get his new Key SP AC-12 to run. The lights and sounds all worked as advertised, but the motors would not run. Naturally, I assumed a broken motor lead during shipping and we discussed sending it back for repair. Fortunately, before he shipped it back, he talked to a friend of his. Turns out this friend had run into the exact same problem on other DCC engines in the past. There is some kind of incompatibility between NCE programming and the EasyDCC system. All the ACs were programmed on an NCE PowerCAB, and he was using EasyDCC. Reprogramming on the EasyDCC system cured the issue just fine. Thank goodness his friend knew about this issue, as I would have been totally lost when the engine came back and worked just fine on my NCE system (as it had before shipping). So here's the second tip:

 

If the sound and lighting work just fine on a DCC model, but the motors won't run on your EasyDCC system, try reprogramming the decoder(s) CVs on your EasyDCC system.

 

Finally, the third problem involves shorting on a high current capacity DCC system. My NCE system is capable of 10A, so you can almost weld with it. Twice now, once a few years ago and again last night, I have had insulators on wheels actually break down into low resistance shorts. The first time it happened was on a NWSL 36" steel wheelset on a passenger car equipped with lighting. The insulator on the axle literally melted and the wiring in the car burned up as it tried to handle over 8A. The car was not even running at the time. In the second case, I was running a light engine when it suddenly when solidly short. Of course I assumed a blown decoder, but diagnosis showed it to be one of the tender trucks. At that point I thought a brake shoe or something had come into contact with a wheel. Failing to find any such thing, I disassembled the truck and discovered one wheelset was dead short. The outside edge of the insulator was carbonized and conductive. In other words, the insulator had essentially burned to conductive carbon on the outside face. Cutting off the outside face of the insulator and back filling with epoxy fixed the short.

 

I think what is happening in these insulator breakdown cases is unique to DCC. It is well known that high frequency AC can break down weak insulators and cause a short. DCC is actually AC and my be able to do the same thing. It is rare, so it would not have been obvious when DCC first came out, or when testing DCC. Insulators with slight flaws can obviously allow a faint leakage current across themselves on AC and so also on DCC. With high current systems, this leakage could get worse and worse as more current is carried across the flaw until finally a catastrophic failure occurs. It is so rare that I see no reason to panic even though I have experienced it twice. Just be aware that it can happen and add it to your troubleshooting list when a short occurs suddenly on a previously good running engine or car.

 

Gary

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