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Jerry-

You wrote:
As you can see, your former advice of "I doubt you will find a cheap decoder that will accomplish your goal of running older 4135s type sound units satisfactorily in analog and digital modes" turned out to be incorrect (thanks to the Mr. Koopmann's circuit) as I have now been successful in finding exactly what I had been looking for (a $15 decoder that works with my 4135S LGB Sound Systems) PLUS I have been successful in doing it within my stated goals of "frugality and no desire for technical reading."



My advice was incorrect? You should know me better than to think I would provide you with incorrect advice. :D" border=0> Since all decoders have PWM motor outputs, none of them can satisfactorily power an older LGB analog sound unit. In order for a voltage-synchronized sound unit to work with a PWM supply signal, you need to add a filter.

Considering the design constraints communicated in your initial request, recommending you construct a filter circuit seemed to be out of the question. If I remember correctly, you originally wanted a single decoder to power the 4135S and an LGB Forney. You wanted the decoder to plug into the Forney’s DCC Interface and you did not want to modify/change any LGB electronics. The decoder had be 100% LGB compatible, including compatibility with older MTS serial devices, and it had to be programmable via LGB equipment. You also wanted the loco speed and sound unit chuff speed to be synchronized in both analog and digital modes. The solution had to be cheap and could not involve technical reading.

Needless to say, you have relaxed some of the constraints outlined in your original request. Judging from your posts on the various fora, you have performed quite a bit of technical reading â€" reading LGB Telegrams back through 1996, Digitrax decoder manuals, Sierra-Soundtraxx technical bulletins, etc. You have also polled the members of these same fora.

My original advice was quite accurate:
http://groups.yahoo.com/group/LGBFamily/message/4325

Since you did the research, performed the testing, and decided which compromises were acceptable, you have successfully engineered a solution to fit your design requirements.

Best regards,
Bob
 

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Posted By bobgrosh on 07/18/2008 12:07 AM
Jim...
I am a little surprised that the DH123D decoder works in an LGB rail truck. It can not handle the smaller motor in the LGB field railway locos, but then that smaller 5 pole motor does have a higher stall current than the regular 7 pole LGB motors. I've never tried using the HO decoders with the single motor regular LGB locos, even though the 1.5 amp decoders should be enough. Have you ever pulled any cars with that truck? ...Or stalled it?
If it works in the truck, I bet it would work in a LGB trolley.




Bob, I haven't tried pulling cars with the truck, but I have pushed several cars with it with no problem. Jim
 

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...You conveniently try to suggest that you know everything about what I have been trying to do even though you have never once asked me what I want to do and you conveniently fail to mention that I have never once asked you for any help whatsoever. I have not ever asked you for your opinion on anything and I have never asked you for your recommendation on anything. The only thing I have ever asked from you has been for you to go away and to leave me and my posts alone. ...


Let me take this opportunity to remind all forum participants that this is an open forum. By posting a question on MLS, you are implicitly asking any and all forum members for their personal insights and opinions. What you do with those opinions is entirely up to you. If you don't like the advice (or advisor), simply ignore it and move on.

Gentlemen, move on.

Later,

K
 

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Jerry,

(1) Where do you get all those cheap analog sound cards?
(2) How much do they cost you?
(3) Are they still available?
(4) What will you do when you run out of them. (Or do you have a gross of them tucked in the attic?)
(5) Do you have one or two you'd like to sell?
 

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Discussion Starter #26
Hi Bob,

There is one right now on eBay:
http://cgi.ebay.com/LGB-4135S-STEAM...hash=item230271898677&_trksid=p3286.m14.l1318

These LGB sound cars have been a secret of mine that I have avoided mentioning before (to avoid competition).

I used to pay up to $100 for the cars and I had a friend who bought all the cars for $50 each after I took the sound unit and speaker out. This was on the European 4135s/41352 (steam) and 4235s/42352 (diesel) cars.

Now I usually only bid up to $75 and sell the cars to a different friend for $25 each.
Either way my net cost has been $50 per sound unit.

For awhile TrainWorld had been selling them on closeout and I bought a quantity from them (again with a net cost of $50 per sound unit).

The American 4267s/42672 (diesel) and 4367s/43672 (steam) sound cars are a lot harder to find and I kept the American cars but removed the sound units from them.

The sound cars have been long discontinued but they continue to pop up regularly on eBay.
The earliest cars had no volume control (there is a LGB Telegram that shows how to add a volume control switch). Later cars had a volume control.

Bear in mind that these are chuff only analog sound units and they may not meet everyone's expectations but I am quite happy with them for many applications.

I should also mention that there is a slight difference in the width of older and newer cards and this can make the difference in (for instance) fitting or not fitting in the tender of a LGB Forney.

Also worth mentioning is that there is not any sort of chuff frequency adjustment so if one wants to try to match the chuff rate to a particular locomotive it is not possible. I have played a little bit with resistors with minor successes but I do not have enough experience to make any sort of observation or recommendation. I also have noticed a bit of chuff rate variance between different (same model) sound cars and the label on the LGB sound car box does not always accurately indicate which model sound unit is actually in the car (naturally diesels will always have diesel sound units and steam units will always have steam sounds). A 41352 marked box may have a 4135-35-1 or a 4367-35-1 card in the car. A REAL 41352 marked sound card will be "decoder ready" to accept a LGB 55020 or 55021 decoder IF you want to put a $100 decoder onto a $50 sound card (here I would probably side with my critics and buy a $150 sound decoder instead).

I have never sold any LGB sound units but I do happen to have just purchased some SoundTraxx Sierra sound units from Ohio Valley (on closeout of course) so I will be replacing the 4235s cards I have in four USA NW-2's and in a USA GP-9 with the Sierra sound systems. They are diesel sound units and I would consider selling a few of them for $50 including the speakers if you are interested.

As for what I will do if I run out of them, I doubt that will ever happen because they seem to keep showing up on eBay and I expect more will continue to show up as some people convert to MTS/DCC and want a digital sound system as well. Normally I try to always have one more steam and one more diesel unit than I actually need.

Good luck,

Jerry

Posted By bobgrosh on 07/22/2008 5:34 PM
Jerry,
(1) Where do you get all those cheap analog sound cards?
(2) How much do they cost you?
(3) Are they still available?
(4) What will you do when you run out of them. (Or do you have a gross of them tucked in the attic?)
(5) Do you have one or two you'd like to sell?
 

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The 150 ohm resistor is most likely to limit the inrush current of turning the sound decoder on and off via the rt input.

The bipolar cap and the resistor simulate the motor load to the decoder. Don't use a lower wattage!

Regards, Greg
 

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Jerry, you used "it" in an ambiguous manner, so I do not know if you are referencing the 150 ohm resistor, or the 220 ohm 1 watt.

The simple answer is no, it's not a good idea.

Also, when connecting the 9 volt battery, the 150 ohm resistor is not used, referring to your diagrams.

So, maybe I'm misunderstanding.... use 9v battery between SW & RT (by the way, the polarity is not marked, a concern), no 150 ohm resistor... ok...

Leave the relay and switch to speaker out .... definitely ok...

220 ohm resistor and nonpo cap, needed... although you could make a nonpo cap out of 2 polarized caps, but they would be pretty big, and you need different values, contact me if you cannot find the right cap.

Regards, Greg
 

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Discussion Starter #34
A few people have asked how I manage to power my layouts with both analog track power and alternatively with MTS. It was very easy to do.

Bear in mind that I don't do anything with MTS/DCC other than to control the decoders in the locos or sound units.

Perhaps these images will help:











The LGB Jumbo gives me 10 amps to the mainline under analog track power and under MTS the mainline gets 5 amps from the LGB Central Station III.

The Inner Loop gets 6 amps with analog track power from the LGB 51070 or 5 amps under MTS from the LGB 55090 Power Extender.

Jerry
 

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Jerry-

Nice installation pictures.

I have a few questions:

1. Did you happen to measure the DCC current draw of the sound unit (at full volume) now that the decoder/filter is installed? It would be interesting to see how this value compares to the current draw of the unmodified analog sound unit (at full volume). Since the resistors are heating, either the unit now pulls more current or the maximum volume is slightly reduced. Or maybe neither!

2. Does the chuff rate change when the volume is adjusted on a DCC layout? (Set the decoder to a given speed step, say speed step 8. Adjust the volume potentiometer. Does the chuff rate remain constant? Or does the chuff rate slow down as the volume increases.)

Thanks!

Best regards,
Bob
 

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Jerry-


1. I never did make or buy one of the suggested circuits to measure DCC voltage or amps so I have no idea what the DCC voltage or amps are.



You don't need anything special to measure the current draw.

You can place an ammeter in line with the AC feed to the MTS central station. Simply measure the difference in current draw bettwen the modified (decoder/filter installed) and unmodified (no decoder/filter) units.

Best regards,
Bob
 
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