No Smoke problem

[Slawman]

I have for some time had no working smoke generator in my DEV Spreewald. Many years ago, something went wrong and the generator overheated (melted a bit of the stack) and stopped working. I recall this failure coincided roughly with my installation of an LGB 55021 decoder.

I have run some diagnostics and seem to have found a (the?) problem. The smoke output terminals are outputting 13 vdc rather than 5 vdc. Before I proceed with a workaround I thought I would put it to the forum in case there is some easy fix here that I am missing?

Here's a few pics in case that helps:

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View media item 3209

 

[Neil Robinson]

My understanding is the default value for the decoder F1 pin is full track voltage. The LGB circuit board should reduce this to around 5V for the smoke unit.
To me this suggests that the loco (as opposed to the decoder) board has a problem or that there is an error in the smoke unit connections.
Try resetting CV 49 to 5 then connect a good 5V smoke unit directly to the decoder using the F1 pin and the V+ pin next to it on its left when viewed with the motor and track wires at the bottom. I suggest a good unit as, and I'm guessing, the decoder terminals may need a load to get a sensible reading.

 

[PhilP]

Wot Neil say's..
That is a very early board in the loco.. Later ones had regulation for lights and smoke, so you did not need to change the divider CV for the F1 output. - You may find you need to up CV 49 to '6' to get a decent amount of smoke.
Don't overly fill the smoke unit.

 

[Slawman]

Thank you Neil, CV 49 is currently set to 32 to accommodate the decoder interface which I am using. I agree that this appears to be a problem with the LGB electronics. All other functions work fine ie. the 5v output to all lights. I will give your suggestion a try, I would rather use the decoder output (bypass the LGB electrics altogether) if that is an option..

I am also considering using the 14v feed and dropping it to 5v using a converter, this seems to work fine on the bench.

 

[Slawman]

Wot Neil say's..
That is a very early board in the loco.. Later ones had regulation for lights and smoke, so you did not need to change the divider CV for the F1 output. - You may find you need to up CV 49 to '6' to get a decent amount of smoke.
Don't overly fill the smoke unit.

Thank you Phil, I was writing my post when your comment came in. I am unclear on exactly what CV 49 does in reality and will play around today with that as you guys suggest. I was thinking it simply disabled the decoder direct voltage output from the pins if you were running lights etc. through ye olde LGB electrics?

 

[PhilP]

CV 49 is the 'voltage divider' value for the 'F1' decoder output..
Value can be from '0' to '32' - 32 being 'full track voltage', so each increment of the CV value will give you 1/32 of track voltage.

So for a nominal track-voltage of 24V each increment will be 24 / 32 = 0.75V

So, if CV 49 = 5, then the output would be 5 x 0.75 = 3.75V (a little low).
If CV 49 = 6, then the output would be 4.5V.

If your system gives a lower track-voltage, then you would need a higher value for CV 49 to get closer to 5 Volts.

 

[Neil Robinson]

I am unclear on exactly what CV 49 does in reality and will play around today with that as you guys suggest.

Take a look at Page 31 of this document, hopefully it's the appropriate document for your decoder. N.B. CV 49 has different functions and values for different decoders.

https://www.champex-linden.de/lgb_p...BBF200AAA0FEE85256BDB0057F3E1/$FILE/55021.pdf

 

[Slawman]

Results: The resetting of CV49 did not have any impact on the issue however I have made some further observations.

Activation of F1 will trigger the regulated voltage to the pins, it is when F1 is off that the output switches to 14v. ie F1 on 6v, F1 off, 14v.

The mechanical switch in the loco cab has no impact. Is the Switch dead?