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pauliebanger

Dapol Class 122. DCC sound decoder issue.

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Hi Everyone,

 

I've had a problem with a Dapol Class 122 model and wonder if anyone else has experienced something similar.

 

The model requires a 5 or more function 21MTC decoder. I fitted a ZIMO MX644C (MTC compliant) but the interior lights are permanently illuminated.

 

I fitted a Loksound 21 MTC with the same result.

 

I tried a TCS non-sound 21 pin decoder and this operated the interior (coach) lights as described in the instructions.

 

(AUX 3 operates the coach lighting and is a Logic Level output on MTC compliant decoders).

 

Has anyone fitted a sound decoder to one of these models and been able to switch the coach lights off using the decoder, not the physical switch on the model?

 

Kind regards,

 

Paul

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Ah !  The wonderful MTC-21 pin standard,  so popular that there are two different versions of the standard kicking around the industry !!

 

In one version (used by European decoder makers) the higher Aux functions are logic-level. 

In the other version they are full-voltage.  

So, a decoder built to supply the logic-level can't work the full-voltage, or visa-versa.  

 

I've tripped over it with US outline locos, their lights work fine with US (eg. TCS) decoders, but don't work when European (eg. ESU/Zimo) sound decoders are fitted.

 

Your description implies that Dapol may have adopted the version which uses full power for higher Aux functions, not the logic level version.  

Only fix would be additional components/rewiring of the Aux circuits in the model, or, if there is space, inserting a MTC21-to-MTC21 board between decoder and loco socket, with that board containing the transistor switches to step up the logic outputs to full voltage - this would be the easiest to remove subsquently if there is space to fit it.

 

 

- Nigel

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Ah !  The wonderful MTC-21 pin standard,  so popular that there are two different versions of the standard kicking around the industry !!

 

In one version (used by European decoder makers) the higher Aux functions are logic-level. 

In the other version they are full-voltage.  

So, a decoder built to supply the logic-level can't work the full-voltage, or visa-versa.  

 

I've tripped over it with US outline locos, their lights work fine with US (eg. TCS) decoders, but don't work when European (eg. ESU/Zimo) sound decoders are fitted.

 

Your description implies that Dapol may have adopted the version which uses full power for higher Aux functions, not the logic level version.  

Only fix would be additional components/rewiring of the Aux circuits in the model, or, if there is space, inserting a MTC21-to-MTC21 board between decoder and loco socket, with that board containing the transistor switches to step up the logic outputs to full voltage - this would be the easiest to remove subsquently if there is space to fit it.

 

 

- Nigel

 

Nigel,

 

If only the complication was that simple!

 

I have highlighted the mismatched standards applied to '21MTC' decoders in the recent past (Dapol 0 gaugeClass 08) so I do understand the point you are making. But this issue has another layer.

 

The lights are permanently illuminated with either an MX644D (which has open collector on Aux 3 and 4) or MX644C which has Logic Level on Aux 3 and 4. The ESU Loksound 21 pin decoder also has Logic level on Aux 3 and 4.

 

Dapol's instruction sheet says it requires logic level on Aux 3 for the coach lighting to be controllable, and shows provision for 'always on' lighting for decoders with open collector FOs instead (but with reduced brightness).

 

However, recent TCS 21 pin non-sound decoders have Logic Level output on Aux 3 and 4 and the brand new one I used is certainly capable of switching the coach lights on or off.

 

I tested the decoders on my MXTAP decoder tester which allows switching between test state 'Open Collector' and 'Logic Level' so I can confirm the status of Aux 3 and 4 to be as I describe above.

 

To sum up.

 

TCS with Logic Level switches coach lights on/off correctly.

ZIMO MX644D with Open Collector does not switch coach lights on/off, but this is to be expected, according to Dapol instructions.

ESU Loksound with Logic Level does not switch coach lights on/off correctly.

ZIMO MX644C with Logic Level does not switch coach lights on/off correctly.

 

The mystery is why does the non-sound decoder with Logic Level operate the coach lights as expected, but the sound decoders with Logic Level outputs will not?

 

The only clue I have is that the (Logic Level) output current appears slightly higher than that from either of the sound decoders, judging from the comparitive brightness of the LEDs on my MXTAP test board.

 

No wonder the smart money is moving to PluX22.

 

Kind regards,

 

Paul

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With the DJM class 71, there is a similar problem with the headcode lights, dealt with in more detail on the relevant thread. However, I found that the ESU LokSound could work the headcodes, but I had to alter the function allocation to get it to use aux 3 (the headcodes), using JMRI Decoder Pro to make the task easier. 

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Until I got my Dapol 122 I didn't even know there were compliant and non-compliant 21 pin decoders! I am glad I don't have to sort out a sound version. It took me a while to realise with the decoder that I used that f5 turned on the coach lighting.

Tony

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The mystery is why does the non-sound decoder with Logic Level operate the coach lights as expected, but the sound decoders with Logic Level outputs will not?

 

The only clue I have is that the (Logic Level) output current appears slightly higher than that from either of the sound decoders, judging from the comparitive brightness of the LEDs on my MXTAP test board.

 

 

 

Paul,

the report you give is pointing to a voltage issue, perhaps Dapol have two LEDs in series or LED plus rectifying diodes for analogue, and thus needs slightly more volts to light.  That could be tested with a variable voltage power supply, a current limiting resistor, and a few test probes.  (or a digital voltmeter on the outputs of each decoder on your test board would show the actual voltages in question).    If it is a rectifying diode for analogue, then modifications to the Dapol may be not too drastic, provided the owner doesn't go back to analogue.

 

- Nigel

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Paul,

the report you give is pointing to a voltage issue, perhaps Dapol have two LEDs in series or LED plus rectifying diodes for analogue, and thus needs slightly more volts to light.  That could be tested with a variable voltage power supply, a current limiting resistor, and a few test probes.  (or a digital voltmeter on the outputs of each decoder on your test board would show the actual voltages in question).    If it is a rectifying diode for analogue, then modifications to the Dapol may be not too drastic, provided the owner doesn't go back to analogue.

 

- Nigel

 

Nigel,

 

I suspect you are right, which is why I mentioned the differing brightness.

 

If this had been my own model I would have investigated further.

 

Unfortunately, I may never know as the owner has now decided to return it to his retailer.

 

As well as this one, I had an email from someone else last week with similar Class 122 problems. These two could easily be exceptional cases so I wondered if anyone else had experienced the same problems or indeed had successfully fitted a sound decoder.

 

With the DJM class 71, there is a similar problem with the headcode lights, dealt with in more detail on the relevant thread. However, I found that the ESU LokSound could work the headcodes, but I had to alter the function allocation to get it to use aux 3 (the headcodes), using JMRI Decoder Pro to make the task easier. 

 

Hi Jeff,

 

Thanks for your response. I assigned Aux 3 to a spare F key on the ESU with my Lokprogrammer and confirmed with my test board that it was operational before fitting the decoder to the model.

 

There does not appear to be any faults with any of the decoders I tried.(Actually, I used several different ESU decoders and all gave the same results).

 

It seems that the circuit on the PCB was expecting higher output on Aux 3 than either sound decoders were providing. 

 

 

Kind regards,

 

Paul

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Ive fitted mine with a Loksound 4 select with class 101 sound.

 

Ive had to use the switch inside to disable the interior cabin lights as F3 did nothing apart from sound the horn.

Directional and destination box lights work as expected on F0

Cab lights i cant seem to get working as the F Numbers mentioned on the paperwork operate different sound functions

 

EDIT : Cab lights work on F13 and F14. I'll pop the body off when I get chance to see if one of the upper F numbers control the cabin lights

Edited by meatloaf

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Not sound - just lights

I've tried a Gaugemaster Omni 21/8 pin decoder (using 21 pin of course) All I get is f2 which will switch a cab light on for 10 or 15 seconds before turning them off - speed of train stays constant - it is a 1.8A decoder.

 

I removed the original switch panel; or should I have that AND a decoder. I had assumed that the original switch panel was the equivalent of the 8pin dummy for dc. Am I right?

 

I am trying to find a compatible decoder with lights but my supplier doesn't have one!

 

I thought the full DCC version with sound used a Loksound decoder??

Regards

 

Basil

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Not sound - just lights

I've tried a Gaugemaster Omni 21/8 pin decoder (using 21 pin of course) All I get is f2 which will switch a cab light on for 10 or 15 seconds before turning them off - speed of train stays constant - it is a 1.8A decoder.

 

I removed the original switch panel; or should I have that AND a decoder. I had assumed that the original switch panel was the equivalent of the 8pin dummy for dc. Am I right?

 

I am trying to find a compatible decoder with lights but my supplier doesn't have one!

 

I thought the full DCC version with sound used a Loksound decoder??

Regards

 

Basil

 

Basil,

 

TCS have a compliant 21MTC non-sound decoder. I got everything working correctly with one of these but he wanted a ZIMO sound decoder with my authentic Class 122 sound project loaded.

 

Dapol may have had an ESU project created; I didn't realise that there was a factory fitted sound option. However, that's not particularly important as in theory, any 21MTC compliant decoder should operate all the lighting correctly.

 

The fact that is does with some decoders but not others (including ESU Loksound) points to a design or production problem if this is widespread.

 

 

 

I can't answer your specific questions regarding the switches as I no longer have acces the model, but my understanding was that mechanical switches were only required for analogue users.

 

DCC is brilliant for this sort of remote individual switching when it is executed properly in the model. As I made clear, I found these issues with only the one model I have yet handled so it may be a one-off.

 

Kind regards,

 

Paul

Edited by pauliebanger

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Not sound - just lights

I've tried a Gaugemaster Omni 21/8 pin decoder (using 21 pin of course) All I get is f2 which will switch a cab light on for 10 or 15 seconds before turning them off - speed of train stays constant - it is a 1.8A decoder.

 

I removed the original switch panel; or should I have that AND a decoder. I had assumed that the original switch panel was the equivalent of the 8pin dummy for dc. Am I right?

 

I am trying to find a compatible decoder with lights but my supplier doesn't have one!

 

I thought the full DCC version with sound used a Loksound decoder??

Regards

 

Basil

I don't have a sound decoder. I just wanted to control the light functions. The instructions state for this you need a 5 function MTC compliant decoder.

I used a Lenz Silver 21+. This is a 5 function decoder (not 4 as some retailers state). All the lighting functions work. The only departure from the Dapol instruction sheet is that the passenger lighting is f5 not f3. F3 AND f4 with the Lenz are used for shunting and other motor control so f5 is the next available function for the interior lights.

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Here's how I tackled the lighting issues with the Dapol 122, using a Zimo MX644D... essentially:

- standard MX644D

- bridge wire from a 'spare' output direct to the interior light switch

- ensure the interior light switch is in the OFF position

- map a function key to control that output on the decoder

 

I've also avoided using the 20mm round speaker enclosure, as I wasn't at all convinced about its' effectiveness, so have gone with the Zimo small Dumbo LS26X20X08-1W.

 

Full install guide here: http://youchoos.co.uk/Index-Resource.php?L1=Guides&Item=OO-Dapol122

 

Some of the key photos here:

DapolOO122-I.jpg

DapolOO122-N.jpg

DapolOO122-M.jpg

DapolOO122-O.jpg

DapolOO122-U.jpg

 

Enjoy!

John

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What Dapol have done with the circuit board is to by-pass the circuitry handling the logic level output, and ran a parallel feed to pin 17, by cutting the feed from pin 17 (which on some is Aux 5 and can double up for the SUSI). The internal lighting can then be switched via Aux 3 on an MTC decoder.  At a guess TCS doesn't have the SUSI connection and therefore this problem doesn't show up.  The reasoning for putting this by-pass in is to allow the internal lighting to be powered on a DC layout and hence needed that circuit bypassed.

 

Nb. Pin 17 when including the index as pin 11, or the 16th physical pin.

 

Regrads
Kevin

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Not a lighting or sound issue but maybe related to this logic level/ full voltage thing of which I admit to being confused.

 

I had a query about an ECoS 50200 with ECoS detection system, which will detect and display the loco adress from ESU and Lenz decoders straight out of the box, but although it will detect a Hornby sapphire NMRA compliant decoder it will not display its address on screen. Railcom enabled for this scenario.

 

I should add the model in use is a Bachmann 101 DMU.

 

Could someone in the know please explain what this logic level vs full voltage thing is all about and why the 21-pin MTC standard seems to have two levels.

Thanks Rob

Edited by RAFHAAA96

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"Could someone in the know please explain what this logic level vs full voltage thing is all about and why the 21-pin MTC standard seems to have two levels.
Thanks Rob"

 

It's all a very messy story:

 

When Marklin and ESU first teamed up and proposed the 21-pin MTC interface, it was designed to support a number of Marklin specific things, like three motor outputs and 3 motor sensing inputs to support brushless motors, which Marklin was promoting a the time as "Sinus"

 

The initial specification had Auxiliary outputs 3 and 4 at normal amplified levels able to drive lights etc directly, and this information was used in defining the NMRA version of the specification. The NMRA also re-purposed the third motor output and one of the motor inputs as additional functions.

 

When Marklin/ESU released their first loco with 21MTC, they deviated from their own spec and had outputs 3 & 4 as "Logic level", i.e very low current that required external amplification on the loco motherboard to make them drive real loads. The argument for this that I heard was that they could not fit the additional output transistors on the decoder at the time. For a while Marklin followed this practice, even after they broke up with ESU.

 

The ESU interpretation became the basis of the NEM specification, i.e. ONLY forward & reverse lights, and the first two functions can be directly used to drive outputs. The NMRA originally had all the outputs amplified. It is useful to note that the latest NMRA spec, shown as draft on the NMRA website, now conforms to the NEM definition of outputs.

 

As far as I can determine the following is true for outputs 3 and higher:

       ESU is Logic level only per NEM spec

       Zimo has decoder versions that do both logic level or amplified outputs
       Soundtraxx seems to be only amplified
       Digitrax appears to allow logic level or amplified to be configured in CVs
       TCS appears to be logic level per spec in the EU621X, and select-able level in their EU821 decoders. I'm not sure about their sound decoders.
 
What is even more frustrating, is that most manufacturers do not EXPLICITLY state on the locomotive packaging or literature which version of the specification they have followed.
 
And the greatest irony of all is that all the current Marklin decoders, (Remember, this is where the mess started) use amplified outputs, so installing a new Marklin decoder in an older Marklin locomotive is gamble.
 
 
Alan
Edited by sparaxis

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Does anyone know if there are there any sound decoders available now that avoid the need to make hard wiring changes? or does the Dapol wiring make that impossible?

Thanks

Chris

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20 minutes ago, Gilbert said:

Does anyone know if there are there any sound decoders available now that avoid the need to make hard wiring changes? or does the Dapol wiring make that impossible?

Thanks

Chris

Hi Chris, in theory the Zimo MX644C (rather than the MX644D) should allow this, as the FA2 and FA3 AUX outputs on this decoder are logic level instead of full power.  We've had a few reports though that the interior lights remain on even with the 'C', so it may be more complex than that, but that's the theory at least.

Cheers, John

 

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The method I used requires no soldering and only requires the use of an oversized drill bit to sever the track to the side of pin 17. 

This track goes through the PCB to the bottom side.  Just position the drill over the hole at the end of the track  and twist the drill bit in the fingers whilst pressing down to remove the copper from around the hole.

The interior lights can then be switched on and off on the assigned function key.  If you need to revert for use with DC then just push a piece of wire through the hole and solder to each side of the PCB. 

 

Works with the Loksound V4

 

 

IMG_0803_L.jpg

 

Quick video of lighting in action.  Apologies done quickly on I-Phone

 

Cab lighting has been linked to F19 and only illuminates in direction of travel.

Interior lighting is on F12 

 

No changes to function map of the Loksound v4.0  sounds by Legomanbiffo

 

Edited by beejack
add video and photo
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On 04/02/2019 at 17:26, beejack said:

The method I used requires no soldering and only requires the use of an oversized drill bit to sever the track to the side of pin 17. 

This track goes through the PCB to the bottom side.  Just position the drill over the hole at the end of the track  and twist the drill bit in the fingers whilst pressing down to remove the copper from around the hole.

The interior lights can then be switched on and off on the assigned function key.  If you need to revert for use with DC then just push a piece of wire through the hole and solder to each side of the PCB. 

 

Works with the Loksound V4

 

 

https://www.rmweb.co.uk/community/uploads/monthly_2019_02/IMG_0803_L.jpg.15a74c3c4207653b3aae38a66f7c6bb3.jpg

 

Quick video of lighting in action.  Apologies done quickly on I-Phone

 

Cab lighting has been linked to F19 and only illuminates in direction of travel.

Interior lighting is on F12 

 

No changes to function map of the Loksound v4.0  sounds by Legomanbiffo

 

 

An interesting solution, thanks for sharing.  Is this the same mod as referred to on the Biffo 121/122 sound decoder details page ?  What  speaker have you used, sounds good ? 

TIA

 

Edited by tractor_37260

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Yes   it is the same mod although they suggest cutting the track rather than the pass through hole.

The speaker is the standard speaker supplied with the decoder, although the housing is a slimline one which has been sealed with black tac.  I believe it was purchased from DC kits a few years ago but never used until recently.

 

The speaker was mounted on top of the decoder cover by cutting a larger recess to fit the housing.

 

IMG_0815.JPG

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Hi all,
Apologies for re-awakening a slightly old thread, but I've been trying to chip my class 122 and having similar, but slightly different issues to those mentioned above.

 

I'm using a Zimo MX638D, (non sound, and the documentation shows Function 3 as a non-logic level), with a Gaugemaster Prodigy Advance2.


However, rather than the interior carriage lighting remaining on constantly (as others have said), it remains off and none of the function keys appear to turn it on.
The interior lighting works fine on DC with the blanking plate inserted, so it's not a problem with the wiring contacts or circuitry itself.

 

Has anyone else used this decoder (or similar) and seen the same issue? If so, did the mod of cutting the track to pin 17 solve it?
I'm a bit loathe to start hacking the circuit board around in case my issue is something different entirely.


Unfortunately I don't have any other 21 pin decoders to try at hte moment.

 

Thanks for any suggestions you can offer.
Regards
Daniel

 

EDIT - Never mind, I found the exact solution to my problem on anothe thread: Turns out I just needed to re-write CV#8=3 to switch the decoder into 'Logic Level' mode and it all works fine. https://www.rmweb.co.uk/community/index.php?/topic/138294-the-curious-case-of-a-zimo-638d-21-pin-mtc-decoder-and-a-Dapol-class-121/

 

Edited by LittleRedTrain
Found solution to issue.

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