Digitrax DZ125IN 651 NEM 6PIN DECODER

[traction]

Why do these things happen the day before an exhibition?!!!

 

I have a new Dapol Class 153 fitted with a Digitrax DZ125IN 6pin plug in decoder, version 51. It runs perfect using the Bachmann EZ-Command and the PowerCab.

 

I also have a new Graham Farish Class 108 three car DMU and the new Deltic DP1 from the train set, these are also fitted with the Digitrax 6 pin chip, both run perfect with the PowerCab, but no control using the EZ-command.

I can get them to move but that is it, once running the only way to stop is pulling the power from the EZ-Command, also no light functions working.

I have taken a Bachmann 6pin chip and put this into the Deltic and Class 108 and I have full control again.

 

The Digitrax decoder in the Class 153 was bought a while ago, the two others were bought recently.

I have also taken the Digitrax decoder out of the perfectly running Class 153 and tried this in the new Deltic and Class 108 again no control.

 

So a working decoder in the class 153 will not work in the Deltic or the Class 108???

 

It looks like there is something strange going on with the compatibility between these decoders and the EZ-Command, I just can't understand why the working one won't work when put into the Deltic or Class 108

 

If I select the Deltic or Class 108 and they are stopped I can turn the lighting functions on/off no problem, once the locos actually start to move functions can't be changed nor can the direction. Turn the speed to zero, loco keeps running until I stop it and slightly lift it off the track, not enough to drop out the power though! it will then stop and function control will then be ok as will direction control.

 

Any ideas or suggestions, carried out decoder resets on both the problematic decoders still nothing,

 

Cheers

 

Ian

[Edwin_m]

The only thing I can think of is the capacitors/inductors on the Farish PCB. This might explain why the decoders don't work in these models but I'm not sure it would explain working on one command station and not another.

[Nigelcliffe]

Variables other than the loco innards:

 

Track voltage is very different - around 13v from the PowerCab, around 20v for the E-Z (the Digitrax decoder spec says 20v max). Quality of DCC signal from command station. Quality of electrical connection to command station (and if poor quality, causing interference)....

 

I'd draw two lessons, cheap chips and cheap command stations give problems.

[traction]

Sorry Nigel, but the really cheap Bachmann plug in decoder works faultlessly.

 

The two new Digitrax decoders are completely useless.

It's very odd as the other locos with Digitrax Chips work fine with both the EZ-command and PowerCab.

 

Hey ho will try and get hold of a Bachmann decoder at the exhibition.

 

Cheers

 

Ian

[AndrewC]

This may sound a bit obscure but are you plugging into an existing circuit board in the loco? If so grab a meter and check the resistance between the lighting common + (blue wire on the decoder) and each of the pickups. I've had the exact behaviour with some recent Athearn locos and NCE decoders. They ran fine with an el-crappo decoder but went into never never land with the NCE. Once I ripped out the circuit board and hard wired everything the decoders responded properly. As Nigel hinted it may be partly due to a less than perfect DCC signal from the EZ coupled with that signal & voltage being introduced to the function common of the decoder.

[Etched Pixels]

Sorry Nigel, but the really cheap Bachmann plug in decoder works faultlessly.

 

The two new Digitrax decoders are completely useless.

It's very odd as the other locos with Digitrax Chips work fine with both the EZ-command and PowerCab.

 

Hey ho will try and get hold of a Bachmann decoder at the exhibition.

 

Cheers

 

Ian

 

Are you sure the decoders are not simply faulty ? Do they work with a proper (ie certified) DCC control system on another layout or is that something you've not got access to easily to check. If they don't then I'd suspect you've simply got a pair of duff decoders, perhaps with marginal or incorrect components fitted.

 

The other thing I would try before giving up in despair is turning the back emf off on the Digitrax and seeing if that helps. I don't think that is going to be the problem but I've had trouble with Digitrax back-emf doing utterly insane things with the recent sound chips, which seem to be a close relative. On those you get weirdness like speed changing according to what sound is playing and the like.

 

In truth I'm not entirely surprised. Non NMRA certified controllers have a nasty habit of only working truely reliably with the relevant manufacturers decoders.

 

Alan

[traction]

Thanks for the suggestions everybody.

 

I thought the EZ-command was to NMRA standard.

 

Anyway, bought a Bachmann decoder plugged that in and still it was a nightmare.

 

I have used a different AC power supply, still 1amp but I can select voltages of 12, 13.5, 16 and 18v AC.

 

I had it set to 12v which is actually giving out 13.5.

I checked this and turned it up to the 13.5v setting on the power supply which actually gives out at the connector 16.5v AC ( the original Bachmann 16v AC power supply gives out 16.7v )

 

Ran the loco again and it seemed to run perfect! Left it running for about 15mins in both directions and then started to run it slow and turn the light functions on/off all seemed ok, last couple of mins it lost it a bit but it is very odd.

 

I don't know how much difference there is between measuring the voltage from the white and blue wires from a decoder (will need to check that) but on the SMD82 accessory decoder (which connects to the DCC power bus) there is a DC output connection.

 

With the power supply into the EZ-Command at 16.5v AC I was getting a reading of 17.2v DC out of the SMD82!

 

If this is like a decoder I have read that you need to add 1volt to the DC reading to give the rough track voltage.

 

So 'IF' this is the case, using the normal power supply you are getting 18v on the track.

 

Seems very high for N-gauge motors to me!

 

Thanks for some other info Nigel about using a 10v AC supply to bring the track voltage down, I will give that a try.

 

Cheers

 

Ian

[Etched Pixels]

Is the decoder getting really hot when you run the model ?

[traction]

No none of the decoders get really hot that I've noticed, run these in the loco with body off for testing and they don't appear to be too bad.

 

I just don't get it.

 

I have loads of locos with Digitrax, TCS and Bachmann decoders fitted, one has a CT Elektronic decoder installed.

 

They all work fine with both the NCE Power Cab and the EZ-command.

 

I have even taken some of these working ones out of existing locos and put them in the class 108 and these then start to go silly.

 

When I put these new Digitrax ones in the Class108 and run it with the Powercab all is fine as soon as I try with the EZ-command they start to play up.

 

Makes no sense.

 

Like I say I tried with the Graham Farish Class108, Bachmann decoder and Bachmann EZ-command and that couldn't be controlled initially......but then seemed to work after I switched my power supply back up to give the 16V AC.

 

I will carry out some more tests and see if I can pin it down more.

 

I have double checked and measured the voltages again now though.

 

EZ-Command takes a 16v AC input from it's power supply, actual reading is 16.5v AC.

DC output from SMD82 is 17.3v

 

Powercab takes a 13.5v DC input from power supply actual reading is 13.3v DC

DC output from SMD82 is 11.9v DC

 

The SMD82 manual just states that the DC connection is rectified track voltage

 

I don't know what effect reducing the input voltage to the EZ-command would do to the DCC signals, but it's quite a difference in DC voltage from the SMD82, which I would guess would mean the track voltage would also be quite extreme as well.

 

Don't know if it's worth getting hold of a lower output AC power supply and trying it to see what happens.

 

Cheers

 

Ian

[traction]

Just as an Update and to hopefully say it maybe sorted!

 

I used the the Team Digital accessory decoder's DC output as my reference point

This is the rectified track voltage so thought it would be a good place to start.

 

I connected up the Power Cab and that was giving the 11.92v DC on the SMD82 DC output terminals.

My thought was that the Power Cab runs everything on my layout very well, so I would try and get the voltage to be the same from the EZ-Command.

 

I used my own power supply which is adjustable and turned it to the 12v AC setting, it does give out 13.5v but this is still much lower than the original power supply that come with the EZ-Command.

 

I measured the DC output from the SMD82 terminals and I was getting a reading of just over 16v.

 

I made up two strings of diodes each string had 6 diodes soldered together end to end, all running the same direction.

 

I took one of the strings turned it round and soldered the ends to the first string, this gave two strings joined together at each end one string of diodes running one way, the other string of diodes running the other way.

I connected this to one of the wires which runs from the EZ-Command to the track, the other wire goes straight to the track.

 

I measured the DC output again from the SMD82 and now have a reading of 11.87v, which is almost the same as the reading when the Power Cab is connected.

 

Tested the Class 108 with the Digitrax decoder and it runs perfectly........at the moment, need to get the layout fully assembled and will give it a proper test run later, but I couldn't get this far before lowering the voltage.

I've only tried just very slow speed running and stop starts, functions on/off all seems perfect at the minute.

 

So hopefully that was the problem, could be that the new decoders have slightly tighter tolerances set who knows but I think it's better to run at the lower voltage anyway!

 

I did speak to Bachmann technical services and asked about a lower power supply, he did say that I could do it that way and/or add the string of diodes to drop the voltage which I have read about before.

Still it's got the voltage down and so far looks like it may have solved it.

Thanks for all the replies.

 

Cheers

 

Ian