Hi all, I have been using the forums as a great resource for some time, but this is my first post. I'm looking for suggestions on a good solution to an annoying problem -- the lights on my uncoupler masts do not light up.

Here's the situation:

- Light bulbs all work well in tests.
- I have 3 light masts and 6 C-track uncouplers, and it's the same behavior with all of them.

- I'm controlling the uncouplers digitally with a CS2 and a k-74 decoder.
- I know the k-74 is a rare, really old model, and maybe the source of the problem is simply the k74 is not the right tool for the job -- I sort of accidentally bought it on ebay thinking that I was bidding on a newer model decoder.
- However, it seems to be working ok. I was able to program the k74 to a new address and it seems to be receiving commands just fine in DCC mode.
- The uncouplers function, i.e., they go up/down when I activate them digitally, although very briefly--just a quick up/down.
- 99% of the time, the lights on the masts do not come on. Occasionally, I will see a very short flash, but this is quite rare.

Is it possible that the pulse the decoder sends to the uncoupler may be so short that the light bulbs do not have time to light up to a perceptible level? If so, is there any way to change this in my CS2 or decoder settings? I did try to bump up the switch activation time in the CS2, e.g., 1000ms, 2000ms, 5000ms... However, this doesn't give the results I was expecting. Instead of the uncoupler staying the the 'up' state longer, it goes up/down at 0ms, up/down at 500ms, up/down at 1000ms, etc.. I have never tried the uncouplers with a m83 or k83, so I'm not sure... is this the expected behavior when increasing the switching time?

Any suggestions for a fix / cheap workaround or... just get a different decoder? Thanks,
Dan

Hi Dan
A warm welcome to this great forum of Märklin friends
Here are a few possibilities:
- the K84 (6084) is a bistable relay output and is not recommended for use with a uncoupler (you may forget it on). With it you need to provide an external power source to energize theuncoupler.
- the K83 (6083) is a transistor-controlled set of outputs As long as you push the button on your CSx (CS1, CS2, CS3 and keyboard/6021) the solenoid remains activated (and so the light should be). Drawback: if the K83 "misses" the switch-off order from the CS or CU, then the solenoid burns and in return, its burns the output transitor in the M83.
- the M83 (60832) is the up-to-date module to drive the uncouplers. The standard duration is 200 mS so the light will not be seen. It can be programmed for longer activations but past 1.5 seconds, the M83 switches to burts of activation (sound like a submachine gun).

So which is which in your case, I am not sure
Cheers
Jean

Hi Eino

No, on the contrary, these old decoders are especially werll suited for uncouplers and for marklin 7051 cranes
cheers
jean