Light Function Assignment in Zimo MX634D Decoder

[RFS]

Just acquired a DJ Models class 71 and I have a problem getting the lighting to work, in particular the head-codes.  I'm starting a new topic for this because it's specifically decoder-related rather than an issue with the class 71 model.

 

I first tried a Lenz Silver 21-pin decoder but the performance was not good - minimum speed about 4-5 mph and top speed only 55 mph. However all the lights function correctly -

 

F0 - front and rear markers

F1 - cab lights front

F2 - cab lights rear

F5 - head-codes 

 

The head-codes are on function output 3 which the Lenz decoder maps to F5.

 

Instead of the Lenz I've used a Zimo MX634D 21-pin decoder.  Performance is excellent so I'm happy to run with that.  

 

However, although F0-F2 work the lights as per the Lenz I cannot get the head-codes to work. Function 3 appears to be mapped to F3 but they don't come on. I suspect it's a mapping issue but I can't see what.

 

Any Zimo specialists out there who can advise?

 

[Suzie]

Off the top of my head it looks like the headcode lights might be connected to the SUSI outputs so you might need to disable the SUSI bus on the decoder to get them to work as function outputs 7 and 8 (F5 and F6). Set CV124=128 should be the quick and dirty way to get these outputs working - but if you have modified CV124 just add 128 to the current value.

[RFS]

Off the top of my head it looks like the headcode lights might be connected to the SUSI outputs so you might need to disable the SUSI bus on the decoder to get them to work as function outputs 7 and 8 (F5 and F6). Set CV124=128 should be the quick and dirty way to get these outputs working - but if you have modified CV124 just add 128 to the current value.

 

Thanks for your help but I'm afraid it made no difference.  I've tried toggling the function output assignments using CVs 33-46 but to no avail.  The MX634D is defined as having FO3 and FO4 as normal function outputs, whereas the MX634C has them as logic outputs.  You can switch between the two by setting CV8=4 to ensure it's in MX634D-mode, but that doesn't change anything either.

 

The fact that the Lenz works with FO3 assigned to F5 implies the loco is wired correctly. 

 

Meanwhile I've sent an email to Zimo to see if they can advise. 

Edited May 18, 2017 by RFS

[Suzie]

If you do a factory reset and set CV124=128 you should be able to operate all the ten function outputs on a Zimo with F0-F8 with the default mapping (MTC-21 versions like the MX634 only have eight functions connected so two of them won't do anything).

 

Puzzling why it is not working. Does the loco have something clever that requires more than one function active (F0 for example)? Are the headcodes directional?

 

Zimo does allow you to map other function outputs to be directional too, but that is not the default behaviour.

[RFS]

Still no joy I'm afraid so I'll wait and see what Zimo respond with. 

[RFS]

Just to update on this.  The DJ Models Class 71 is configured such that it expects the AUX3 function on the decoder to be a logic output.  The Lenz AUX3 is indeed a logic output and it works fine.

 

The MX634D, however, has all 6 of its outputs as normal function outputs which is why it doesn't work as is.  However a feature of this decoder is that you can switch its AUX3 and AUX4 outputs to logic (ie turning it into an MX634C) by issuing a CV8=3 change. Despite fully resetting the decoder, and then issuing CV8=3, the lights still do not work.

 

I have been communicating with Zimo and they don't know why this is not working.  I have 3 MX634Ds and I tried all of them with the same result.

 

I can only assume the logic output is behaving differently and is not compatible with the DJ Class 71. 

 

So my 2-EPB will keep its MX634D and I'll run the DL 71 from the Lenz  Silver decoder for now. 

[Suzie]

I would measure the voltage on the function output to see what is there while it is operated in the 2EPB with reference to the blue wire. You should see a difference between logic mode and full power mode.