KW Transformer Question...

You should be seeing 0 volts with the throttle closed. There's got to be a voltage leak some where. It's also possible the throttles are not closing all the way.

Put a little load on it when measuring the voltage. Maybe a couple of light bulbs. That way you can see if it is a real voltage. Or just leakage across something that actually has high resistance. 

Sounds like transformer one, the rollers are still touching the last winding of the coil and not reaching the Bakelite coil housing for off. Shift the coil in the brackets to correct. KW's output is actually 18 volts, and not 20. The second transformer hum is caused by a loose coil in the brackets. Use cardboard shims to tighten coil in the bracket and the hum will be greatly reduced or eliminated. Be sure on this one you don't run into the same problem as with number 1 trans.

I agree that this is a transformer issue, likely with the rollers not completely breaking contact with the coil in the closed position.

Here is the service documentation with exploded diagrams: http://www.olsenstoy.com/searchcd31.htm?itm=657

Thanks Everyone.

I checked and cleaned the Bakelite landing of any carbon dust.

The rollers are well clear of the coil when in the off or 0 position.

I did the lamp test (6 volt lamp) and when attached the phantom voltage drops to zero and there is no current to make

the lamp light or even glow a little, until I ramp up the throttle(s).

I'll keep going over the manual drawings BMoran4 sent and maybe do some

isolation tests at some point.

It is some type of very high resistance path or maybe inductance, or I'd have that

magic smoke / cooking smell by now.

Thanks Again! Dave

What kind of meter are you using to get the voltage reading: analog or digital?

It is a digital. I have another digital I can try, but I need to get a new nine volt battery first.

Thanks Dave

David Johnston posted:

Put a little load on it when measuring the voltage. Maybe a couple of light bulbs. That way you can see if it is a real voltage. Or just leakage across something that actually has high resistance. 

Yes, this is normal. You won't see it when connected to the layout.

There is no repair or adjustment to make. Carry on.

It is a digital. I have another digital I can try, but I need to get a new nine volt battery first.

I asked because sometimes digital meters will show voltage on a transformer where an anlog meter would not. I am not well enough versed in electronics to understand or explain what is going on. But I'd guess there are a number of people participating on this chat board to explain what is happening.

Here is a write up on the Granger's web site that might explain the phenomena. They call it "ghost voltages".
Experts, what say you?

Fluke Multimeter Detects Ghost voltages.

I need to look into getting a DVM with that feature.

But the light bulb test work for now.

I guess that one KW has a couple of parallel wires or whatever that

are causing the ghost voltage while the other KW does not.

Thanks Again For All Your Suggestions.

Dave

I need to look into getting a DVM with that feature.

Just remember I wrote: MIGHT EXPLAIN

I like my old school analog VOM's. I have a large unit on my desk that was designed to be rack mounted. It came out of an old hobby shop. And I use a Simpson 260 when I want something portable.