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| | |-+  "0" isn't zero - and now twice more
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Author Topic: "0" isn't zero - and now twice more  (Read 3942 times)
on30gn15


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« on: August 23, 2009, 09:24:49 PM »

Got the Durango & Silverton passenger set the other day and have discovered that when the power controller is set to "0" there's still enough current flowing that the loco will move after being nudged in same direction controller is set for.

Since it won't move when nudged opposite the way controller is set for, it has to be because some amount of current is still flowing.

Looks like leaving is set with controller in "0" would be a good way to send just enough current to overheat the motor and burn it out.

Okay, just dug out the box of light parts and a Miniatronics 1.5v  30ma 1.2mm dia, red bulb will come on when leads touched to rails with controller in 0

This one you definitely want to unplug when it is sitting still.

later,
Forrest Scott Wood
« Last Edit: August 26, 2009, 04:42:42 PM by on30gn15 » Logged

When all esle fials, go run trains
Screw the Rivets, I'm building for Atmosphere!
later, Forrest
Joe Satnik


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« Reply #1 on: August 25, 2009, 12:04:49 AM »

Dear Forrest,

The design of the 44213 power pack

http://www.bachmanntrains.com/home-usa/products.php?act=viewProd&productId=1301

swaps the 2 output leads when the reverse switch is moved, so you should have the same value voltage in both directions.  My guess is that your motor/gear train is stickier in one direction than the other.

Your power pack should go to zero volts. <--ERROR ! See Below

If your unit is under warranty, take it back to your place of purchase or return it to Bachmann for repair or replacement. 

If it is not under warranty, I have a schematic and understand what's going on inside it, and am willing to help.   

I have fixed one by replacing a bad internal component.

Keep us informed. 

Sincerely,

Joe Satnik 

Edit:  Added red error notice

« Last Edit: September 02, 2009, 09:00:54 AM by Joe Satnik » Logged

If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
on30gn15


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« Reply #2 on: August 25, 2009, 12:30:45 AM »

Hey Joe;

Yes, the power pack needs attention.
I'm not much experienced with electronics to find out what's causing this.

Locomotive is probably fine, got same behavior with a super-sensitive HO loco jumpered to G track with controller at 0.
And with the G scale V&T 4-6-0.

Just enough current leaking through to all ow motors to turn over with encouragement.

I've been meaning to get an ammeter and a volt meter for, oh, two decades.
Logged

When all esle fials, go run trains
Screw the Rivets, I'm building for Atmosphere!
later, Forrest
Joe Satnik


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« Reply #3 on: August 25, 2009, 11:39:00 AM »

Well, Forrest,

Meters would help externally, but you would need electronics training to go inside and fix it.

joebarb "at" wwt "dot" net

if you want to discuss off-board.   

Let us know how the warranty turns out. 

Don't let anyone throw it in the trash, though.  I'll pay the postage to have it thrown in my trash....

Sincerely,

Joe Satnik

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If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
on30gn15


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« Reply #4 on: August 26, 2009, 04:46:44 PM »

This is becoming a trend - Glenbrook Valley Summit Pass set and Pennsylvania RR Pennsylvanian set ordered a few weeks ago with that settlement money came today and . . .

With both their power controllers a Miniatronics 1.5v  30ma 1.2mm dia, red bulb will come on when leads touched to rails with controller hard against 0

"Curiouser and curiouser said Alice."
Or, is it 'Annie'?
« Last Edit: August 26, 2009, 07:39:41 PM by on30gn15 » Logged

When all esle fials, go run trains
Screw the Rivets, I'm building for Atmosphere!
later, Forrest
Dave

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« Reply #5 on: August 26, 2009, 05:30:51 PM »

It could be a Pulse unit rather than a Linear.
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renniks


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« Reply #6 on: August 26, 2009, 07:05:55 PM »

Sounds like a wrong component--either a Potentiometer with no dead(disconnect)position or Pots that are incorrectly assembled. Given the apparent lack of quality control in other cases (HO and On30 Shay and Climax gears)it could be either.

Eric UK
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Joe Satnik


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« Reply #7 on: September 02, 2009, 08:58:20 AM »

Dear Forrest,

My apologies to you and the others. 

I made a mistake in assuming the power pack went to zero volts. 

Theoretically the MC34063AP1 "DC to DC Converter Control Circuits" IC chip (the heart of the power pack) can only go to down to 1.25 Volts output.

Vout = 1.25Volts *(1 + R2/R1)  where R2 ranges from 0 to 10K Ohms (Speed control knob or potentiometer) and R1 can be either 770 ohms or if jumpered, 720 ohms. 

This jumper adjusts the upper possible voltage out of the power pack.  I assume this is to make up for sloppy tolerances in the pot and resistors.

The rest of the design limits the current to about 1.0 amp, so cheating on the upper voltage may not help too much.  (Wouldn't stop me from jumpering it if it was out of warranty....)

We could add a diode in series with the output (past the voltage sense point for feedback) to reduce the output by 0.7 volts or so.  This limits the upper voltage, too, so a bit less power out of the pack....

There may be a more elegant fix, but I'm pressed for time right now.

Hope this helps.

Sincerely,

Joe Satnik
 
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If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
Joe Satnik


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« Reply #8 on: September 02, 2009, 10:55:11 AM »

Dear All,

A zero cost solution:

Put the direction switch in the middle. 

There has to be a small "break before make" travel point in the direction switch slide, where the track is disconnected. 

Voila --- zero volts, zero amps to the track.   

I know, kinda cheesy, but in a cheap sort of way.

Down side: no adjustment between zero and 1.25 Volts. 

Hope this helps. 

Sincerely,

Joe Satnik
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If your loco is too heavy to lift, you'd better be able to ride in, on or behind it.
on30gn15


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« Reply #9 on: September 02, 2009, 01:33:25 PM »

My apologies to you and the others. 
I don't think you need to  Grin

It is very good to know that I wasn't delusional - well, at least about that.

Question - dug out both my 26 year old MRC power packs, a Tech II Locomotion 1500 and a Control Master II.
Neither mentions G on the box after all, but do say can run up to 3 HO locos.

On back both say, above 3 terminals, variable DC, fixed 16V AC, fixed 12VDC
"OUTPUT - 20VDC, 17VAC, 22VDC TOTAL - 12VA"

That work for these sets?

Oh, and that famous little red bulb, it doesn't even come on till throttle hits almost 20% throw in its arc.
Logged

When all esle fials, go run trains
Screw the Rivets, I'm building for Atmosphere!
later, Forrest
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