2018_03_25 A change is like a holiday?

2018_03_25  I'm just kidding I think....

Something different to break up the monotony (of rewiring)


 First of all, a Locomotive that was working on DCC well for a year or two, suddenly starting playing up. I opened it up and found these two devices used as suppressors under Aus law, were still connected. One had burns on it. I snipped them out and replaced the connections with plain wire (ends of resistors)  Problem resolved and engine performs well, probably better than it ever has. Moral of story? cut off these two suppressors and the capacity that sits between them when converting to DCC. The capacitor is removed and not bridged with plain wire.

Strange shorts  STILL!!

I was working on the layout and shunted a train away from where I was working. After the job was complete, I turned on the power and of course, I had another short, shutting down this whole area.
I immediately checked all my recent work, testing as I went. I removed all the plug in droppers but short persisted. I went inside and watched some TV. Several days later, I went back to problem solving. I noticed a new SDS guards van was blinking red lights, so I picked it up to look at it, and the short disappeared. It seems the van was sitting on a diamond crossing. Further when I sat the wagon on the main line it worked perfectly. But if I sat it on the diamond, it shorted out the command station once more. I spent an hour or two testing the circuits on the diamond, which were all good. 8 insulated rail joiners one rail each side to red and Black Bus! and two frogs connected to juicer which was showing appropriate lights. However they failed to change colour when an engine drove through.

Houston we got a problem! Anyway I decided to walk away for a while and look at the guards van. But then I noticed it was sitting on the Wodonga Coal siding SG  track not the crossover. So I placed it on the BG track and the short did not come back. Furthermore the diamond was connected to the SG bus, which should have been ok. I will connect it to the main through bus, and see if short goes away.

The SDS van now does not light up, so I decided to take a break and open it up, and see if I could get it working once again.... pictures?  I remembered to take some :)

CLICK PICS to enlarge

This is the SDS van. Its a beaut piece of work and I liked it enough to buy 4 of them.

Line door up with step to refit body

See two small square lugs? They have to be released to remove body.

On this photo almost to verandah see square attaching point on frame? This sits over lugs inside body!

I used 4 bread tabs to release lugs.

So here is the floor. I found two small screws that release weights sitting on top of circuit board.

The weights sit over the capacitor. The two small black cylinders (One under my thumb) have red LED's sitting inside and need to sit under light tubes for lights on body.

Great design. The steps are soft plastic that push aside without breaking.

However the body plastic is rigid, which means the end up rights are brittle. They have to sit outside the iron work and slot into holes in deck. Be gentle when putting it all back together.

Oh? near forgot the brass tabs fit on top of the bogie screws which are passed through the wheel pickups. The power then routes through the circuit board
 The right hand brass tab fell off, so a coincidence rather than a cause of the short. No sign of heat.




But I still am no closer to finding out why the guards van operates everywhere else, but causes a short circuit in the SG  parts of the Coal Siding :(
Cheers
Rod