Using LGB sound board from Uintah/Sumpter loco together with DCC decoder for DCC or DC ??

[beavercreek]

I have embarked on some alterations to my Annie fleet.
At the moment I have done five upgrades on the sound in Bachmann Annies by utilising the cheaply sourced sound boards out of LGB UIntah/Sumpter mallets. These boards' chuff are triggered by hall sensors that I have installed on a tender axle together with magnets placed on a tender wheel.
The power for the board comes from the loco via the socket and lead that would normally power the tender rear light.
Each LGB soundboard has a 'built-in' set of buffer super-capacitors to give standing sounds etc. (for DC operation)
I may also add tender pickup axles to help with any pickup probs for the sound board/loco .

My question is.....
I am thinking of using a DCC decoder in each loco. Something like Massoth XL or an ESU Lokpilot XL etc (both 3 amp)

How will this affect the soundboard? It obviously works on both polarities for DC but not sure how it would fair on DCC:

Will it operate fine from the DCC track power (it obviously works fine from the DC track power)

Would it be best to have the board powered from the decoder or leave it as a separate entity (unless it will not work with DCC straight fro the track).

Will the sound board's 'built-in' caps be okay with DCC (power from decoder or from track). Will they work to overcome any pick-up issue with the sound. They will obviously not be useful for their 'standing sound' operation with DCC but I want to be sure that they will not be damaged by the DCC. They are important when on DC.

Hope someone can give me some guidelines on this.

 

[Railway42]

The best answer is they may be DCC ready but to make sure send the sound board No to Massoth. on a loco like Stains sound board which is not DCC ready the trick is to connect the sound board to the motor. But send an Email to Massoth.

Railway42

 

[Cliff George]

I don't know Mike, I could probably figure it out if I saw the LGB sound board. A board designed without DCC in mind is is unlikly to work on straight DCC. It probably would work from the motor output of a decoder.

I once had an LGB analogue mogul with sound, the only way I found I could keep the sound when converting to DCC was to connect the sound board to the motor output of the decoder. However I soon converted the sound to something more compatible with DCC. Why not just get a sound decoder?

As Railway42 said ask Massoth. Does the board have any sort of serial number?

 

[Tim Brien]

I do not believe that the sound board will run on DCC power input. I would use a DC power output on your decoder (such as smoke function, assuming you are leaving the board at full power output and not decreaswing for 5 volt lighting).

Because you have a Hall sensor then chuff synching will not be an issue as the board will behave the same under control of the decoder DC output using the power cable already in use from the loco to tender. The decoder effectively isolates the sound board from DCC power as you are using a DC output from it.

Edit: you may lose the directional number of toots of the whistle as the polarity will not change with directional change.

 

[beavercreek]

I was thinking of hooking up the board to the motor output from the board but wanted to be sure that the sound board would not operate properly with 'straight DCC' .
Would it not still be directional with this setup (toots different for forward/reverse) as the motor will be sent forward DC voltage from the decoder and reverse DC from the decoder. Would this not be the same as ordinary DC from the track...I may be missing something here though (quite possibly )

The LGB soundboard obviously has a rectifier bridge on board so it is happy with any polarity voltage from the track.

Why not just get a sound decoder?

Well Cliff, I had managed to get these boards for an average of £30 each and their sound is very good (digital sound of Sumpter/Uintah mallet but they are analogue boards). At the time I was updating the Bachmann Annies with these boards I had no intention of DCC-ing them.
But now I have reconsidered and can get some 3 amp DCC decoders cheaply so it would be a waste to rip out the LGB soundboards (with the modifications already done to the tenders etc) and spend another £150 or more on sound decoders to put back in.

 

[Tim Brien]

The thing is that you want to isolate the sound board from the decoder DCC outputs. The cases mentioned as regards analogue sound most likely did not have the Hall effect device to synch the chuff/speed. By using the DC output from the decoder you are simply mimicking DC track power pickup so the board should behave normally as the Hall sensor will control chuff synch.

The decoder motor inputs are NOT pure DC power and as far as I am aware are not polarised DC so cannot see how directional tooting would work. Also, you would be feeding DCC into the sound board. The sound board simply needs a source of constant DC power to operate given that it uses this power through the Hall sensor to clock the chuff.

By using the DCC as an input, the sound board capacitors may cause a problem for the decoder.

 

[beavercreek]

Tim and Simon, many thanks for your input.
So I can get it clear in my little mind..
1) The motor outputs from the decoder power the motor and also give it the polarity to go forward or reverse BUT the DC motor output from a decoder is not really 'pure' DC . It is a form of PWM and that is also what and Aristocraft powersupply can deliver with analogue DC. My Aristo PWM has not problem with the soundboard so hopefully the decoder motor output PWM should be fine as well

2) The sound board will work off the motor outputs from the decoder

3) The sound board capacitors may behave differently than if they were having track 'pure' DC fed to them

4) The sound board capacitors may degrade with the 'non' pure DC given out by the decoder.

5) The capacitors will not 'feed back' any voltage to the decoder as the soundboard circuitry ensures voltage from the capacitors only feeds the sound board amplifier in case of break of power supply to the sound board. BUT the caps are utilised only for standing sounds and breaks in supply so they should act the same if the motor outputs from the decoder has a break due to eg bad track contact or the loco is at rest.

 

[Tim Brien]

By using the DCC as an input, the sound board capacitors may cause a problem for the decoder.

No - its the sound board which will have the problem.

Yes, I definately agree. Personally, I would use nothing but pure DC on a LGB sound board. PWM has been known to destroy LGB boards. Using a DCC source to power the board is also suspect. This is why I initially suggested using a DC output on the decoder such as the smoke function to power the sound board.

 

[beavercreek]

Tim and Simon, many thanks for your input.

I did already post this up in number 8 but I really want your wisdom on what I said and it may be lost as you have moved on lads. Hope you do not mind the repost

So I can get it clear in my little mind..
1) The motor outputs from the decoder power the motor and also give it the polarity to go forward or reverse BUT the DC motor output from a decoder is not really 'pure' DC . It is a form of PWM and that is also what and Aristocraft powersupply can deliver with analogue DC. My Aristo PWM has not problem with the soundboard so hopefully the decoder motor output PWM should be fine as well

2) The sound board will work off the motor outputs from the decoder

3) The sound board capacitors may behave differently than if they were having track 'pure' DC fed to them

4) The sound board capacitors may degrade with the 'non' pure DC given out by the decoder.

5) The capacitors will not 'feed back' any voltage to the decoder as the soundboard circuitry ensures voltage from the capacitors only feeds the sound board amplifier in case of break of power supply to the sound board. BUT the caps are utilised only for standing sounds and breaks in supply so they should act the same if the motor outputs from the decoder has a break due to eg bad track contact or the loco is at rest.

 

[Tim Brien]

My apologies as I believed that you had made an opinion that points (1) through to (5) were 'facts' and did not require discussion.

Cliff will be your man as to what constitutes a decoder motor input but it definately is not DC power. As far as I am aware the only DC power on a decoder is the function outputs and this is why I suggested a function output with F1 (smoke) generally having the higher current draw capacity to power your sound board.

 

[Cliff George]

It is true that the motor output of most decoders is not pure DC but a form of PWM where the decoder puts out a series of max amplitude pulses, with variable gaps between ther pulses. It is easier to do in the electronics.

The output on the decoder functions will be the same.

There was one decoder manufacturer that offered a pure DC decoder, I think it might have been Zimo.

I think that just about the best Mike can do is to connect to the motor output of the decoder, direction changing features of the sound board will them work. However it is true that PWM may not do the sound board much good.

Mike you can get an add on SUSI sound board for £50.00, not £150!

 

[beavercreek]

Mike you can get an add on SUSI sound board for £50.00, not £150!

The problem is that to rip out the sound board that I have installed complete with hall sensor etc and then buy a combined sound decoder for £150+ or a separate decoder with a sound decoder for about £100 seems a little excessive if I can get the LGB soundboard to operate with just the expense of the £45 quid decoder.

If the outputs from most decoders is PWM on all outputs then that will be similar to the output from my Aristocraft TE supply. This Aristo PWM supply has worked fine with the LGB soundboards in the Annies since last year when I installed them. So maybe they should be fine ........but of course you never know with electronics...what works in one scenario can be totally different in another.

I will test one loco on DCC to see if the sound board is happy before I commit to DCC the rest.

 

[Cliff George]

That sounds like a good strategy.

 

[Neil Robinson]

Mike, you are probably aware and it may be irrelevant but according to a downloaded copy of the instructions for a 20882 loco switch 1 of the bank of four dip switches on the board I assume you have selects analog mode (ON) or digital mode (OFF). I guess this may switch out the storage capacitors together with any other changes that may be needed.

http://www.champex-linden.de/lgb_pr...63C66E4EE743185256930007176AF/$FILE/20882.pdf < Link To http://www.champex-linden...7176AF/$FILE/20882.pdf
page 9 in particular.
Edit, added link to instructions

 

[beavercreek]

Good man Neil,
I had totally forgotten those little dip switches. I had made sure that switch (1) was on when I installed the boards but since then they had slipped from my mind.
The switch of course may just switch out the track contacts and route the power-in to the plug that would come from a decoder.
I am not sure how the switching off/on of MTS (DCC) with switch (1) will affect the caps (as their one good use during DCC would be to cover any loss in track contact) but it gives another parameter to play about with!

 

[Railway42]

Hi if you want DC to run your sound board use a bridge rectifier ac to the track 470uf 63v capacitor +to+ -to - ,the output will too high so run this through a LM7824 or LM7818 this will give you the 24v or 18v that is good enough to run your sound board. the output con be improved with a .1uf and a 470uf across the output if you want.

Railway42

 

[beavercreek]

Hi if you want DC to run your sound board use a bridge rectifier ac to the track 470uf 63v capacitor +to+ -to - ,the output will too high so run this through a LM7824 or LM7818 this will give you the 24v or 18v that is good enough to run your sound board. the output con be improved with a .1uf and a 470uf across the output if you want.

Railway42

The board has a bridge rectifier on board (sorry about the pun) already. It is working off track voltage of both polarities at present.

I tested one of the Annies with both DC PWC (Aristocraft's version of PWM) and also DCC :
The loco did not really like being on DCC as it has not yet got a decoder and this made the motor 'sing' but the soundboard worked in both directions and the capacitors charged up and supplied the soundboard with power after the DCC power was switched off.

I don't know the long term effects but it seems that the soundboard should behave when the decoder is installed and the soundboard is hooked up to either the motor out pins.