TPC 300 Power Cuts Out When Running #41 Army Switcher

I had a similar issue with my Lionel track cleaning car, it would shutdown the TMCC direct lockon.

I fixed mine by putting 1uf-NP capacitors from the brushes to ground on the motor.  The AC motor brush noise appears to be the issue.

I'm thinking a couple of different thing than Gunrunner. Check to see that the uncoupling plate on the lead trucks are not hanging down and brushing the center rail when crossing a track switch. Also the pick-up arms and rollers are not bouncing up and touching the frame, or bridging the center rail. Does the 41 do OK if you are using a postwar transformer with a standard Lock-on? The Electronic Lock-on have a processor controlled circuit breaker, and shuts off the track power before you even see a spark.

The uncoupling plates and pick-up arms seem to be fine.

I'm not actually using an electronic lock-on ... just a standard lock on with the TPC-300 (and a post-war ZW).  When I run the #41 with just the transformer, or using a Powermaster instead of the TPC-300, no problems.

The TPC has a similar quick acting electronic circuit as the TMCC direct lockon, which is why I brought it up.  Note that all the TMCC equipped locomotives with AC motors have the capacitors I mention, which is another clue to the fact they may be needed.

If I get around to it, I'll connect a TPC-300 to my test track and see what happens with an AC motor that isn't bypassed.

"The TPC has a similar quick acting electronic circuit as the TMCC direct lockon, which is why I brought it up. "

To the best of my knowledge, there is absolutely no current sensing in a TPC, except for the thermal circuit breaker.  If you have information to the contrary, please educate me!

Well Dale, perhaps I sit corrected.   I always thought that the TPC had a power sensing circuit. 

For sure it has electronics that is handling the power, so it could still be sensitive to the noise from the AC motor brushes.  It's easy enough to test my theory, simply shunt the brushes of the #41 with the 1uF NP caps and see.

I didn't say that the TPC wasn't sensitive to voltage transients, just that I think it doesn't have any current sensing.  I have had trouble running some of my PW trains with my TPC with the same symptoms.  I have added internal bypass capacitors as you suggested, and also added TVS devices.  This can also cut down on the amount of pickup roller sparking.

If you look at the voltage transients on an old Pullmore motor, they are frightening!

I realize you didn't say it wasn't reacting to the transients, and I didn't mean to imply you did.

I suspect the caps would go a long way to solving this particular issue.

I looked, and I think you're right, I find no reference to anything about current sensing with the TPC.  IMO, that's pretty short-sighted on Lionel's part, it would be easy to fry the thing with a short.  Clearly, it's mandatory to have some over-current protection downstream from the TPC!

I would also expect some current protection, but I have yet to see a TPC with a blown output Triac!  I remember one Forum member was asking about the identification of the Triac (trade name Alternistor made by Teccor), but I never heard if he bought a replacement and it solved the problem.

I have seen TPCs with blown power supplies, but that is quite another problem.

dwp425  gunrunnerjohn is correct.  One of our members had an old sound car that caused our club's TPC400 to cut out.  He fixed it with a capacitor.  Dale is an expert on TMCC components so listen to him.  I can state that I, and our club layout has no faster acting device to cut power when there is a short then a TPC - that is why only the TPC will shut off when these older cars go across a switch or crossover.

John, I think you have figured out that you cannot "PASTE" pictures here. You UPLOAD them via the "Add Attachment" feature built into the forum software. Your previous post looks like you did it right!

Here's one I did just as you were posting yours.

Click on the picture and it will display full size.

I fixed your post so the diagram shows in the window.

Although it was stated briefly, the capacitors must be Non-polarized. I don't think Radio Shack carries these.

Al

Good point, I should have put that in CAPITAL LETTERS!

Thanks for your help.  I'll give this a try!