Troller dual power pack

[sd75i]

   I bought a troller dual power pack that doesn't work.  Has anybody fixed one of these and what was problem?  Thanks

[wm3798]

Probably not worth it.  The "Pulse Power" these were advertised with 30+years ago actually cause problems with N scale motors, or at least that's what I've been told.  Throw it back to the seller, then get a new MRC if you're doing DC.  They aren't that expensive.

Lee

[Carolina Northern]

These are actually excellent packs. Mine's been going strong since the late 70's and has never damaged a motor, which can't be said about the pulse in 70's style MRC packs. I ran mine until I went DCC this year. It's still on the workbench for pre-chipping work. The only thing I never liked was the terminal lugs. Replaced it with a more conventional terminal a long time ago.

The Kato pack that you hear so much about is a virtual copy.

The dual packs are actually two separate  packs internally - the only thing common is the power cord. This is where to start if both sides are out.

To do work inside, you'll have to drill the rivets. I'd suspect the cord or the circuit breaker first.

PM me any other symptoms and I'll try to help you. 

Don

[peteski]

Interesting views from 2 extremes.

I never owned a Kato power pack but I read that it is a pure DC pack with not pulses. Is that how the Troller works too?

[Carolina Northern]

Pete,

I always heard it was a "Pure DC" pack, too. The waveform on the scope is anything but. It looks like it has a half wave riding on the DC level that shrinks into the DC level the voltage rises - exactly like the Troller ( and later Hogger) packs.

Attached is the schematic I got off the Sumuda Crossing site. I believe he still has waveforms from multiple packs on there. Interesting read.

Don

[peteski]

The schematic doesn't lie.  It is a very simple and totally unfiltered transistor-based throttle.

So, the output is 120 Hz (fully rectified) ripple which is always present (from 0-100% throttle setting).  Interesting. It is just like the old school throttles but instead of rheostat it uses a transistor.

If the Troller is just like that, then I don't see how it could be damaging to a DC motor.

[Carolina Northern]

Pete,

The Troller is the same, but with older components. I don't recall the transistor at the moment, but remember thinking it was an oddball back in the old days.

I remember replacing a blown one with a TIP 21 (or was it a TIP22?) when I was doing repairs for a hobby shop (long gone), owned by a friend.

A 1000uf cap will filter it nicely, but then you have the resulting voltage rise.

Don

[peteski]

Pete,

The Troller is the same, but with older components. I don't recall the transistor at the moment, but remember thinking it was an oddball back in the old days.

I remember replacing a blown one with a TIP 21 (or was it a TIP22?) when I was doing repairs for a hobby shop (long gone), owned by a friend.

A 1000uf cap will filter it nicely, but then you have the resulting voltage rise.

Don

Yes, a cap would raise the voltage to probably around 18V DC.  I suppose one could add some resistors in the transistor's bias side to limit the output voltage.  But to me the 120 Hz ripple seems very beneficial. It acts like gentle pulse power to get the motor's armature running smoothly at any speed..

[mmagliaro]

I don't see any reason to put a filter cap on it anyway.  I haven't seen a motor yet, expensive coreless included, that doesn't run just a little bit better, and creep an engine just a little bit slower, with some half-wave ripple in the DC.
And that sine wave ripple isn't hurting the motors, so why not just leave it.

As for why the OP's doesn't work, yep, I'll throw in with drilling out the rivets, opening it up, and then check for broken wires, fuse, or breaker.  You can use a voltmeter to just trace along the path from the output of the main transformer all the way to the output terminals.  If you don't see any broken wires, try testing across the fuse or breaker with an ohmmeter to make sure it's not open.   Then turn it on, up to half throttle, set the meter on AC Volts with a range up to 20 or so, and see if you have voltage coming OUT of the main transformer.  NOT THE SIDE WITH THE POWER CORD HOOKED TO IT!  The OTHER side, where the low voltage comes out.

If that works, switch to DC Volts and check after the rectifier, and so on.  If the circuit is that simple, it won't be hard to fix.

If you open it up, and you are stuck, take some photos of the insides, good and close, and I bet we can help you get to the bottom of the problem.  We can circle things on the photo and show you where to test.

Or should I say, "I" would do that for you.  I don't want to speak for anyone else.

[peteski]

I
If you open it up, and you are stuck, take some photos of the insides, good and close, and I bet we can help you get to the bottom of the problem.  We can circle things on the photo and show you where to test.

Or should I say, "I" would do that for you.  I don't want to speak for anyone else.

There are several members here familiar with electronic circuits and willing to help (speaking for myself). 

As long as the questions are posted in the appropriate section of the forum. 

[Rich_S]

The schematic doesn't lie.  It is a very simple and totally unfiltered transistor-based throttle.

So, the output is 120 Hz (fully rectified) ripple which is always present (from 0-100% throttle setting).  Interesting. It is just like the old school throttles but instead of rheostat it uses a transistor.

If the Troller is just like that, then I don't see how it could be damaging to a DC motor.

My question, why are they using the POT to control the transistor, what advantage does this have over simply controlling the current and voltage with the potentiometer? Is the transistor being used as a filter? 

[Carolina Northern]

Had to jump off last night.

Without a complete electronics lesson, older packs (like the famous MRC trottlepacks that we all used in the sixties) used a rheostat that dropped the voltage with a wire winding, dissipating any unwanted voltage as heat. These had to be taper wound to give smoother control and matched to the motor they were controlling. This is why there were different models for different scales - the size and current draw of the motors.

The transistor in simplest terms, acts as a switch with the pot controlling how much on or off the transistor is (again - simple description). This isolates the voltage from the load giving the same control, no matter what type or number of motors) being controlled. One of the things I did in the late seventies and early eighties was to rebuild MRC 501's by removing the rheostat and adding components to make it a transistor throttle for local modellers.

The bad rep that pulse had came from the method used in the early packs to perform this. This consisted of cutting off one half of the bridge, forcing a 60 Hz (remember when cycles per second became hertz? I was already working electronics at the time. It was hard to adjust  - still slip some times - tried to type cps just now.) half wave AC output with symmetrical off time. This shook the motors.  MRC championed this idea and it worked well with the old open frame (mostly Pittman and copies) motors. When newer, lower current motors started to appear, the 60 Hz half wave output destroyed these - thus the bad rep.

The website I referred to has pictures of waveforms and some of the insides. The interior view of the 501 shows the rheostat in the upper left. The website is not easy to find things on, so here's a link to the page

http://www.sumidacrossing.org/PhotoAlbums/ElectricalSystemsPhotos/DCTestingPhotos/

Don

[sd75i]

Here is unit

[Carolina Northern]

OK, that makes things a bit clearer.

That is the full deluxe pack with all the bells and whistles.

The momentum circuits will make it harder to troubleshot. I have not personally ever been inside one with momentum.

From the picture, you have the momentum turned on for both sections.

Before you do anything, turn it off and try the throttle again. You can use your meter on DC volts the 20 volt range should work for this. With the Harbor Freight meter, the knob should vary the output from zero to 12 volts on a functioning on of these. If this doesn't work, drill the rivets and post a picture of what you have inside. I'd expect a small circuit board attached to the terminals and a second board with the momentum circuits on it.

We'll see if we can't get it working without the momentum and go from there.

Don

[Carolina Northern]

Well, my memory is failing. I found my old notes from when I worked on these. The original transistor is a BDX53B. Seems to be a lot more common now.

My notes say I used a TIP31, not a TIP21.

My notes show the circuit to be almost identical to the Kato, but the values of the pot and resister are different. The pot is a 1K linear and the bias is 220.

Don