MFX / DCC Help - LGB 20752

wandgrudd

Registered
24 Oct 2009
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51
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Having a bit of trouble with an LGB mfx loco the LGB 20752.

I had it happily running on address 3 out the box back in January on a test track but have come to use it now and it started acting up I put it on the track and it went shooting of on its own without being selected on the controller (Full Massoth setup) and then came to a stop.

It now refuse to respond to any commands and wont allow any CVs to be altered, I can read the CV’s fine but they aren’t what I was expecting ie, CV1 says 7 when it should be 3 (but doesn’t respond to 3 or 7), CV29 = 39 should be 6 etc…

I understand the need to do proper CV programming with MFX locos rather than the quick change address method but I haven’t even been able to get to alter anything yet with this loco, everything else on the track including one other MFX loco continued to work fine for the rest of the day as they had been the hours beforehand.

Any pointers before I give PandS a ring?
 

idlemarvel

Neither idle nor a marvel
13 Jul 2015
2,597
724
Ascot
Can you read CV 50? That tells you protocol the decoder will process (mfx, Motorola, DCC, analog). I assume you don't have an mfx capable controller so you probably want DCC only or DCC / analog.
 

wandgrudd

Registered
24 Oct 2009
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wandgrudd

Registered
24 Oct 2009
402
51
....
Can you read CV 50? That tells you protocol the decoder will process (mfx, Motorola, DCC, analog). I assume you don't have an mfx capable controller so you probably want DCC only or DCC / analog.
No havent got an MFX controller, i will have to have a check of CV50 and report back.
 

wandgrudd

Registered
24 Oct 2009
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phils2um

Phil S
11 Sep 2015
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Ann Arbor, Michigan
Good luck getting it sorted! Hopefully you wont be doing to much of this -:banghead::banghead::banghead:
 

wandgrudd

Registered
24 Oct 2009
402
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Good luck getting it sorted! Hopefully you wont be doing to much of this -:banghead::banghead::banghead:
Does seem to be a unique little loco mfx wise, haven’t had any issues with any of the other new mfx locos as long as your carful with how you alter address etc. will have to do some experimenting and report back.
 

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
28,106
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Tamworth, Staffs.
If CV29 is set to greater than 32, then it is looking for a long address...

You can change CV1 to anything you want, but the loco will not respond to it.

PhilP
 

wandgrudd

Registered
24 Oct 2009
402
51
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If CV29 is set to greater than 32, then it is looking for a long address...

You can change CV1 to anything you want, but the loco will not respond to it.

PhilP
Right so if that’s the case, CV29 read out as 39 yesterday (despite me not altering it) I should then be able to read CV17 and CV18 and back calculate the address its looking for ?
 

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
28,106
2,895
Tamworth, Staffs.
Right so if that’s the case, CV29 read out as 39 yesterday (despite me not altering it) I should then be able to read CV17 and CV18 and back calculate the address its looking for ?
Yes... Though a Google should find you a calculator, that will make it easier for you..

As you have said, change individual CV 's, rather than use (say) the address change option on a Massoth system.

PhilP
 

KentKeith

Registered
24 Oct 2009
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1,616
SouthEast Kent
The procedure that I always use for setting-up new LGB mfx locos on my Massoth is to set up the following CVs, in this case for my new toy (DFB 704) with the address 704:

CV50 = 2

CV29 =38

CV17 =194

CV18 =192

Being lazy I use my (indoors) Roco Z21 to calculate the values of CV17 and CV18.

In addition I normally lower CV63 to around 200 as I find the factory setting to be somewhat on the noisy side.
 
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Dan

Registered
28 Jan 2010
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36
Eastern MA
What I see missing in the instructions above is checking for the Massoth system to be set to the correct speed step. If speed steps of command station and decoder do not match, then all bets are off for other issues.
 

wandgrudd

Registered
24 Oct 2009
402
51
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Just to update this, I didn’t write anything down, but CV 50 comes back with some random number (19 I think), the long address comes back to something like 1930 but still refuses to run on that number, nothing happens under analog power, it’s strange as its been proven that this particular chip doesn’t allow certain CV settings to be altered but appears somehow to have altered them (going by the instruction booklet and other members results) thus I assume the chip has gotten corrupted somewhere down the line, going to have one more go at reading the CV so can send of an email to Paul @ P&S otherwise its going back for LGB to look at it.
 

wandgrudd

Registered
24 Oct 2009
402
51
....
You need to solve your service mode programming problem first.

Can you reliably read and write another decoder on the same programming track.

Greg
Yes and Yes, generally do all my programming on a section of track at the side of the central station but also have accesses to the pc module, so will give that a go at the weekend as I haven’t tried it with this yet, at least with that I should be able to get a full read out of all cv setting rather than one by one. It has to be something unique to this loco as I have been playing with some of CV settings on another MFX decoder fitted to the lgb 20120 and I can do everything I would normally be able to do fine with that, I would have expected this to be of similar chip type as its another of the LGB cut prices offerings.

1619592339482.png
 

phils2um

Phil S
11 Sep 2015
882
361
Ann Arbor, Michigan
Do you know someone or dealer with a Märklin CS3 that could take a look for you? Remember we have found that Märklin's mfx decoders must be last run on a DCC system in order to not get garbage when reading (and writing?) CVs using a DCC system. A decoder reset on a Märklin Central Station, followed by operation by the CS3 with mfx disabled using the default DCC address 3 should get it back in a state where you can deal with it using your Massoth PC module. I don't know if mfx can be disabled on a CS2 which would allow this to be done with a CS2 also.