Author Topic: Walthers F7 (Factory DC) LM-2S Install and Question  (Read 2982 times)

melarson

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Walthers F7 (Factory DC) LM-2S Install and Question
« on: November 09, 2016, 01:39:52 PM »
Having received an ABBA set of Walthers Great Northern F7s for Christmas last year (my wife always knows what to get me  ;)), earlier this year I set about installing LM-2S modules in them.  Initially I thought all was good as they seemed to run well.  But quickly I discovered that as they ran, they kind of sputtered.  They would occasionally, randomly, stall briefly for a fraction of a second.  They would stop motion and the sound would cut out, then quickly recover motion and eventually reset the sound.  I thought at first that it might be a problem with the pickup system (though they have 8-wheel pickup) which didn't please me, but recalled that per Walthers recommendation I ran them each for an hour to break them in, on DC and prior to the LM installation, and they ran perfectly.

I made sure both the wheels and track were clean and yet they still sputter.  Not all at once mind you, but individually, at different times and places.  There was a time when I thought it might be related to unpowered frogs (at our club layout) but the sputtering was so random and inconsistant I had to rule that out as well.

So, last weekend I took them to my DCC installer guy (whom I go to for difficult installs like brass steamers) and we investigated pretty much everything we could think of.  He went through one of the B units from top to bottom, cleaning, adjusting, aligning, you name it.  Still it sputtered.  Finally, and based on my responding to his question that they ran perfectly on DC, he removed the LM-2S and plugged in a Digitrax DH-123.  The engine ran perfectly with no sputtering.

So now we're curious.  The only theory we can come up with is that perhaps, for some reason, the LM-2S doesn't get along well plugged into the factory board (where the 9-pin connector originates from).  He's thinking perhaps there is some sort of weird feedback situation going on that affects the LM but not the DH decoder.

So my question to you all is, has anyone here experienced this in any of your installs where you plugged an LM into a factory board?

In the mean time, of course, I am having him remove the factory board and hard-wiring a 9-pin in the test B unit.  I expect to hear from him soon on the success or failure of that solution and will report back when I do.

Here are some pictures of how I installed the LM originally so you can get an idea of what all is in this thing.  The pics are of the lead A unit but all the units are essentially the same (save for the lack of lights in the Bs).

The unit fresh out of the box with the shell removed:
(the factory board in question is the one in the middle, mounted above the motor.  The board at the rear of the unit is just the 9-pin version of the jumper connector that allows DC operation)
 [ You are not allowed to view attachments ]

With the speaker enclosure removed and the components gathered:
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Feeding the speaker wires through the enclosure access and soldered to the speaker:
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Speaker enclosure reassembled:
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Enclosure reattached to chassis, 9-pin connector rerouted, and LM plugged in and secured:
 [ You are not allowed to view attachments ]

--Michael
« Last Edit: November 09, 2016, 01:47:14 PM by Michael Larson »

Alan

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #1 on: November 09, 2016, 01:57:53 PM »
There appears to be a choke (coil) in series with the motor. Why? What does it do? Seems to me a series inductor might play havoc with RP PWM.
Alan

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When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

melarson

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #2 on: November 09, 2016, 03:57:42 PM »
There appears to be a choke (coil) in series with the motor. Why? What does it do? Seems to me a series inductor might play havoc with RP PWM.

Alan,

Interesting observation!  Not sure if it is in series with the motor just from looking at the pic but if it is then yes, why would it be there?  What would be the purpose of filtering out higher frequencies from the motor when, as you say, it's bing controlled by PWM.  A really good reason to dump the board and wire direct. Makes me wonder about why the Digitrax decoder works fine, though.  Does not DCC also use PWM?  Maybe RP uses a higher frequency?  Maybe RP is just less forgiving of such a device?

Anyway, good catch, thanks!

--Michael

Alan

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #3 on: November 09, 2016, 04:23:19 PM »
I think RP uses a higher frequency PWM than DCC. Basis for their claim of 1000 speed steps whereas DCC is 128. Just guessin'.
Alan

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When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #4 on: November 09, 2016, 07:45:25 PM »
The choke (and associated capacitor/s, they'll be there somewhere) are for reducing RF interference to your everyday household electronic devices.

Back in the good old days of open frame and especially pancake ringfield motors you could actually hear the RFI being generated by the motor on close by radios, and TV's would have wonky noise bars. Quite a few countries required some sort of RF filtering on models and it's carried over to this day. Now, this RF filtering can (and does) cause all sorts of problems for decoders. How badly I guess depends on the quality of the decoder, some seem to cope with the RF filtering and some don't. RailPro it seems could be in the doesn't category. I have a Walthers loco so I might chuck a LM-2S into it can see what happens.

My advice, and you'll find this repeated everywhere on the net is on any model that you can see RF filtering (choke/s inline with the motor and capacitor/s across the motor) get rid the RF filtering. Modern quality decoders should do any RF filtering needed. RP should do this filtering as well.

- Tim

Alan

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #5 on: November 09, 2016, 07:54:10 PM »
And now we have the answer! Makes perfect sense. Thanks Tim.
Alan

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #6 on: November 10, 2016, 01:38:02 AM »
And now we have the answer! Makes perfect sense. Thanks Tim.

Your welcome  ;D I guess you don't see this onboard RFI suppression much in US models.

I did try an LM-2S in the Walthers loco I have (with RFI suppression fitted). Yep, the LM-2S hated it, awful buzzing from the motor and it wouldn't move until the throttle was at about 60%. To be semi complete I then put in a TCS decoder I still have lying around to see what would happen. More buzzing but it moved at a much lower throttle setting so even TCS didn't like the RFI suppression. I might try bypassing the board and see how it performs but I'm in no hurry to do that.

- Tim

melarson

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #7 on: November 14, 2016, 05:25:34 PM »
Update.

Heard from my installer regarding pulling the factory circuit board and wiring the LM directly.  He said the unit now runs very well with no sputtering.  He is going to do the other B unit and then we will take them to the club layout and run them for a couple of hours and see how they do.  Having passed that test, he will then do the A units (more time consuming because of all the lights, hence the reason to test the B units first).

Next time I will know better and dump the factory board right away.  Live and learn!

Thanks to all who took part in this discussion.

Michael

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #8 on: January 28, 2017, 11:21:20 PM »
I chunked all the factory P2K and BLI boards that were in my locos so I can't comment on before and after. Glad to hear it all worked out Mike!

Jacob
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melarson

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #9 on: January 30, 2017, 03:22:58 PM »
Well, about that.

Turns out that even removing the boards didn't help.  With the LM-2S connected directly to the motor the engine still exhibited this erratic stalling behavior.  It's somewhat baffling, because now it appears that it has to be either the module or the motor.

I talked to Tim about it at length a couple of weeks ago.  He gave me some other things to try, chief among them is trying an LM-3S.  I'm now waiting on the results of that test.  Sheesh, I'm starting to think I may need to replace the (brand new, factory) motors if this latest test fails.

Will keep you posted.

Alan

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #10 on: January 30, 2017, 03:41:54 PM »
Connect an LED (with series resistor) in parallel with the motor. Connect another LED/resistor combo in parallel with the truck feed wires. You now have a essentially a test light on both sides of the module. By watching how the LEDs react when the loco stutters you can determine where the problem lay.
Alan

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When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

melarson

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #11 on: January 30, 2017, 04:19:09 PM »
Interesting idea, I will pass that along to my installer, and I'll post the results.  Thanks Alan!

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #12 on: February 03, 2018, 04:30:37 PM »
Has anyone heard back from the author of this thread as to whether (and how) his installation problem was solved?  I realize this is an old topic, but I found the discussion very interesting.  Unfortunately the author, melarson, does not appear to be on the rpug member list, so I'm not clear how to ask him/her directly.

JimW

Michael Larson

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #13 on: August 11, 2018, 01:04:49 AM »
Has anyone heard back from the author of this thread as to whether (and how) his installation problem was solved?  Unfortunately the author, melarson, does not appear to be on the rpug member list, so I'm not clear how to ask him/her directly.

JimW,

My apologies for the very late response.  I had in fact removed myself from the list for a while as I needed a vacation from trains, controls, discussions and such.  I am thankful to Bill for letting me re-join.

That said, here is the status of these units: they've been safely packed in their original boxes and have not seen the light of day since February 2017.  Reason is, I just got tired of fighting them.  In all likelyhood (and at the risk of being kicked of this forum for heresy :) ) I will eventually put Soundtraxx decoders in them and move on.  Since they work flawlessly with a DCC decoder, it is the easiest "solution."

With the amount of engines I have, I reconciled a long time ago that I will forever have a mix of systems.  I am hopeful the scale will tip in RP's favor, but time will tell.

Michael
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jimw

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Re: Walthers F7 (Factory DC) LM-2S Install and Question
« Reply #14 on: August 12, 2018, 06:08:15 PM »
Michael:

Thanks for your kind reply.  I too am in slow-mode, since I have to build the train room before I can build the layout.  My simple 5 ft. test track on a shelf just isn't very interesting (sigh).  I too have faced difficulty with installation, but that is due to my inexperience and to the very tight space inside a P2K SD9 shell.  After finally getting it all back together, it ran intermittently, so I had to re-solder several wire splices: success!

I am also waiting for better steam sound files before cutting out the factory electronics from my fleet of boiling-water locomotive models.  Maybe, like you, I'll settle for a mix of Railpro  and DCC.  Fortunately, I'm in no rush.  Nonetheless, I look forward to reading more of your progress.

JimW