troller autopulse potentiometer

[toptech]

I have had a Troller autopulse twin transpak 5  for 30+ years. The track 1 potentiometer seems to have gone bad. Only has 4-6 DC volts & then jumps to 9-12 DC volts at the plug in track terminals when control knob is turned. Problem is Troller went out of business in the 80's. I'm looking to where I can get a replacement pot. Part # on the pot. is 1377722 . Also has T0107 on it.
 I have found several at an electronics store but do not know what OHM's reading should be at closed throttle to full throttle. This Troller does not have the momentum or braking features. Can not find a cross reference for this part #. Any help would be appreciated.   Bob

[nkalanaga]

Maybe unsolder the wires from the Track 2 pot and measure it?

[peteski]

Maybe unsolder the wires from the Track 2 pot and measure it?

That is a good idea as none of the numbers shown seem to indicate a valid resistance value.

Bob, are you sure the marking is T0107 and not T0102?  I ask because 102 would indicate a 1k ohm pot.

Does the pot have a 1/4" diameter shaft?  If and when you take it out, try too post a photo of it.

[toptech]

 Yes, has T0107 stamped in the metal cover. Plastic shaft is 1/4" with a flat for control knob.

[peteski]

Yes, has T0107 stamped in the metal cover. Plastic shaft is 1/4" with a flat for control knob.

If 107 was a code for resistance that is not realistic  for this circuit (either 100M ohms or 107 ohms which is not a realistic value).  So you still need to unsolder the leads of the working pot and measure its resistance across the outer terminals.

[MK]

It might be possible that it's just a dirty pot.  Do you have any DeoxIt or something similar?  Worth trying a clean before replacing.

[peteski]

It might be possible that it's just a dirty pot.  Do you have any DeoxIt or something similar?  Worth trying a clean before replacing.

That is an excellent suggestion to be tried first. Simpler and quicker than replacing it. 

[toptech]

 Can not be cleaned. The pot has a burnt smell. I took it out today & the shellacked fiber board in it crumbled. Needs replacement. When I posted this originally I was hoping there would be someone who has repaired these that would know what OHM  replacement pot to use. This was easy to get out, lots of room. To unsolder the track 2 pot, to get a reading is almost impossible. Mass of wire harness lies right on top of it. I'm afraid that some wires will get melted. These must have been assembled on a bench & then stuffed into the metal transformer box.  Bob

[peteski]

Assuming that the pot #2 is wired to the circuit board then trace and unsolder the wire at the PC board, not at the pot. You only need to disconnect one of the wires on the outermost terminal.  Then rotate the wiper so it rests at the outer terminal still connected to the circuit. Then measure the resistance between the disconnected terminal and the opposite terminal.

The fact that the pot is burned up doesn't sound good. Unless you know why it happened, there might be a problem elsewhere in the circuit.

[glakedylan]

i have a Troller, not sure of the model, but can take a look tomorrow
if you are interested, glad to send it to you
i have no use for it
would be glad that it is being used


let me know if interested
i am pretty sure i know which box to look in, since our move some months ago


sincerely
Gary

[randgust]

Throttles like this end up regularly on Ebay, too, if you just want to keep an eye out.

I picked up 'spares' for my two anticipating failures that have yet to happen, and paid like $20 apiece.

[glakedylan]

let me know if you want one

[mmagliaro]

I think 1377722 means:

manufacturer code 137 (which is CTS)   
year 1977 (the "77") 
week 22.
So that pot was made in the 22nd week of 1977.

That still doesn't tell us what the resistance value is, but I sent the info to CTS's "technical support" contact.  Maybe
we will get incredibly lucky and they will actually answer me.  That "T0107" number is probably their own code.
EDIT:  It just occurs to me that T0107 is probably a Troller proprietary number (as in "Troller part number 107").
CTS will not likely still have a record of that stamping if they did a custom run for Troller, but we can always hope.

It would also be helpful, I think, if you could post some close-up photos of the case and all the bits and pieces of that dead pot, just in case we see a number somewhere on it that you don't happen to see, or we interpret a number differently.

[toptech]

Here's some pictures. Went to electronics store & they unsoldered POT for track #2 & came up with a reading for a 1K ohm POT.  I have installed a new 1K ohm POT for track #1. Had a 0-15 output volt reading at track terminals when turned on. Put a loco on the track, went 3', new POT smoked when it had a load. Not the loco because it runs perfect on track #2. There has to be another problem. Also terminal with orange wire (pencil pointing to)  has broken off from part that pencil is pointing to. This happened when I unsoldered the second smoked POT.  Looks to be in a heat sink. That part is now bad. I don't know what it is. Track #2 works great, will power 3 KATO F3's fine. AC & DC acc. terminals work fine also.
  The white plastic POT shaft has #145 molded on it. I don't see any other #'s or letters anywhere. There has to be another shorted part somewhere.
  Also I would like to THANK  "glakedylan" for letting me acquire another Troller from him. For some reason this sight will not let me contact him.

[peteski]

Ouch!  Yes, it sure looks like another part is defective causing the pot to smoke.  I suspect the power transistor (the part with the broken lead with the orange wire.

You might want to read through this thread where we troubleshoot another similar throttle. While it won't solve your problem, it will be educational.

The lead that broke off was the center lead (which is a collector of that transistor. It was also electrically connected to the tab which is attached to the metal heat sink.  So if you have a multimeter, we can still test whether the transistor is defective (I expect that it is shorted).

If you google "how to test a transitor" you will find lots of useful hints. Here is one:
https://www.electronics-notes.com/articles/test-methods/meters/multimeter-diode-transistor-test.php

From what we determined in the other thread I pointed you to, it is a NPN transistor.
Here is the pinout (use the heatsink tab as collector).