Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Hi all, probably a basic question, but will a digital loco also run on M track with an analogue transformer? Thanks for info on this. I'm returning to Marklin after decades of absence. |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Yes. Make sure to use a modern transformer 6647, 6647x, 6646 with modern digital locos. Don't use Märklin transformers with a metal case.
And welcome to the forum. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: H0  Yes. Make sure to use a modern transformer 6647, 6647x, 6646 with modern digital locos. Don't use Märklin transformers with a metal case.
And welcome to the forum. Very kind, thank you for helpful info and for the welcome - the digital aspects of Marklin are completely new to me. Regards, Chris K |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
 1 user liked this useful post by ChrisKenna
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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In my experience, modern digital locos outperform pure analogue locos. However, a digital controller is required to change settings of a digital loco for analogue operation. Analogue operation is normally enabled ex works, but it is possible to tweak the settings.
You can set the starting voltage of a loco to e.g. 6 V. Then at 5 V, you will see the lights and maybe even hear the engine sound, but loco will start moving at 6 V. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 04/02/2021(UTC) Posts: 480 Location: USA
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Reversing of digital locs with older (blue) marklin transformers may damage the decoder because that voltage pulse may be 24V or more. So, only use white marklin transformer, like 6646. |
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Joined: 28/07/2004(UTC) Posts: 9 Location: Westfield, MA
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so can a 6627 be used for digital locos or is that also one that can fry the electronics? |
Peter |
 2 users liked this useful post by Peter S
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Joined: 04/02/2021(UTC) Posts: 480 Location: USA
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Originally Posted by: Peter S  so can a 6627 be used for digital locos or is that also one that can fry the electronics? Best to use a voltmeter on red+brown to test reverse voltage. Ben |
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 3 users liked this useful post by BenP
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: H0  In my experience, modern digital locos outperform pure analogue locos. However, a digital controller is required to change settings of a digital loco for analogue operation. Analogue operation is normally enabled ex works, but it is possible to tweak the settings.
You can set the starting voltage of a loco to e.g. 6 V. Then at 5 V, you will see the lights and maybe even hear the engine sound, but loco will start moving at 6 V. Reply from Chris: many thanks for this very helpful advice |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: BenP  Originally Posted by: Peter S  so can a 6627 be used for digital locos or is that also one that can fry the electronics? Best to use a voltmeter on red+brown to test reverse voltage. Ben Very helpful advice, thank you |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: BenP  Originally Posted by: Peter S  so can a 6627 be used for digital locos or is that also one that can fry the electronics? Best to use a voltmeter on red+brown to test reverse voltage. Ben Very helpful advice, thank you |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 28/07/2004(UTC) Posts: 9 Location: Westfield, MA
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Originally Posted by: BenP  Originally Posted by: Peter S  so can a 6627 be used for digital locos or is that also one that can fry the electronics? Best to use a voltmeter on red+brown to test reverse voltage. Ben Okay. What is the max voltage before it becomes a problem? |
Peter |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Originally Posted by: Peter S  Okay. What is the max voltage before it becomes a problem? The nominal reversing voltage of a 6647 is 24 V. I measure 25 or 26 V on mine. The specification of many decoders only allows 28 V. One of my blue transformers has 31 V reversing voltage - while a nominal reversing voltage of only 23 V is given. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 04/02/2021(UTC) Posts: 480 Location: USA
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Originally Posted by: Peter S  Originally Posted by: BenP  Originally Posted by: Peter S  so can a 6627 be used for digital locos or is that also one that can fry the electronics? Best to use a voltmeter on red+brown to test reverse voltage. Ben Okay. What is the max voltage before it becomes a problem? Frankly. I have not tested what is too much that damages decoders, but 24-26V reversing pulse worked fine. Some old blues I used to have (all discarded) give over 30V, but never used for operation of decoders (for obvious reason). Ben Edited by user 08 November 2024 23:59:48(UTC)
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: BenP  Reversing of digital locs with older (blue) marklin transformers may damage the decoder because that voltage pulse may be 24V or more. So, only use white marklin transformer, like 6646. Hi, thanks for helpful info. Is a blue plastic Trafo 37540 (included in a starter set) seen as an older transformer, so not recommended for digital locos? - is the max voltage for reverse the issue? With thanks, Chris |
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 1 user liked this useful post by ChrisKenna
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Joined: 15/12/2005(UTC) Posts: 3,590 Location: Spain
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Originally Posted by: ChrisKenna  Hi, thanks for helpful info. Is a blue plastic Trafo 37540 (included in a starter set) seen as an older transformer, so not recommended for digital locos? - is the max voltage for reverse the issue? With thanks, Chris
As already mentioned by other people, 28Vac is the max if you want to be sure not to damage the electronics. Any blue trafo could be dangerous for the decoders. But there is a work-around; If you can meassure the AC voltage of the reverse-pulse, and then drop it with pairs of anti-parallel diodes. Each pair will drop the voltage by about 0,7V. As these diodes costs only a few cents, -and are obtainable anywhere- you have an easy and cheap way to get up and running, even with older blue trafos. |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: hxmiesa  Originally Posted by: ChrisKenna  Hi, thanks for helpful info. Is a blue plastic Trafo 37540 (included in a starter set) seen as an older transformer, so not recommended for digital locos? - is the max voltage for reverse the issue? With thanks, Chris
As already mentioned by other people, 28Vac is the max if you want to be sure not to damage the electronics. Any blue trafo could be dangerous for the decoders. But there is a work-around; If you can meassure the AC voltage of the reverse-pulse, and then drop it with pairs of anti-parallel diodes. Each pair will drop the voltage by about 0,7V. As these diodes costs only a few cents, -and are obtainable anywhere- you have an easy and cheap way to get up and running, even with older blue trafos. Hi Henrik Many thanks for kindly sharing this info - your electronics know-how is much appreciated. I'm waiting for a newer white trafo also, but in the meantime thought I would ask about the current blue 37540 to be on the safe side. Thanks again, Chris |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 25/08/2012(UTC) Posts: 251 Location: South East
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Chris - I run analogue but I still have a dozen or so digital locos of various decoder types from a previous digital layout. I used the method mentioned by Henrik above and used three pairs of anti parallel diodes in the output from a plastic blue transformer. It reduced the voltage by about two volts. The digital locos survived ok and it had the added benefit of making the control knob position match those on my white controllers for a given speed. I have since gone to all white controllers but it did work ok at the time.
Obviously there are no guarantees so you have to accept the risk. Since you're getting a white transformer it may be worth waiting but the workaround does work. Just be sure to measure the output voltage after the diodes with a meter to be sure it doesn't exceed the 28v maximum.
Cheers, Paul |
Marklin HO using M track. Now reverted to analogue as I find it has more character and is more fun...... and I understand it! |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: Paul59  Chris - I run analogue but I still have a dozen or so digital locos of various decoder types from a previous digital layout. I used the method mentioned by Henrik above and used three pairs of anti parallel diodes in the output from a plastic blue transformer. It reduced the voltage by about two volts. The digital locos survived ok and it had the added benefit of making the control knob position match those on my white controllers for a given speed. I have since gone to all white controllers but it did work ok at the time.
Obviously there are no guarantees so you have to accept the risk. Since you're getting a white transformer it may be worth waiting but the workaround does work. Just be sure to measure the output voltage after the diodes with a meter to be sure it doesn't exceed the 28v maximum.
Cheers, Paul Great, Paul, many thanks for sharing your experience and knowledge, very helpful. Interesting to see from your post that you're committed to analogue - so far, I've not caught up with digital Marklin, since not progressing from the 1960-70s. Let's hear it still for LPs too.... Regards, Chris |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 25/08/2012(UTC) Posts: 251 Location: South East
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Hi Chris, I did succumb to the dark side and went all digital about ten years ago. I bought some digital locos and converted the analogue ones that I had. It was great for a month or so then I found that I was losing interest. The whole hobby had become sort of 'sterile'. I found I was starting to take things seriously and running the layout like a model railway. After another month or so I packed it all away. Last year I dug it out again and converted the locos back to analogue except for the ones that were originally digital. I put together a small layout incorporating some basic switching and automation (very basic) and run it like a train set - which is what it is. It's now fun again. I have a laugh and the interest is back where it should be - and I once again understand what every bit does and how it works. Obviously each to their own but personally I prefer the analogue operation. I suspect I'm in the minority but there you go... It also gives me an excuse to hunt for and resurrect some of the classic 'old clunkers'.
Cheers Paul
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Marklin HO using M track. Now reverted to analogue as I find it has more character and is more fun...... and I understand it! |
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Joined: 15/11/2023(UTC) Posts: 56 Location: Alberta, Calgary
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Originally Posted by: Paul59  Obviously each to their own but personally I prefer the analogue operation. I suspect I'm in the minority but there you go...
Cheers Paul
Hi Paul, As one of the members of the minority, I can only confirm. I have only 10 locs, but all good old style analog ones, and all on M-rails! I just enjoy riding them using classic old blue transformers, and some classic automatics with relays... Minority or not, I enjoy the playing... Kind regards, Herman
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Joined: 25/08/2012(UTC) Posts: 251 Location: South East
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No arguments from me Herman, I'm with you all the way. Enjoy the playing - having fun is what it's all about. Take care Paul |
Marklin HO using M track. Now reverted to analogue as I find it has more character and is more fun...... and I understand it! |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: Paul59  Hi Chris, I did succumb to the dark side and went all digital about ten years ago. I bought some digital locos and converted the analogue ones that I had. It was great for a month or so then I found that I was losing interest. The whole hobby had become sort of 'sterile'. I found I was starting to take things seriously and running the layout like a model railway. After another month or so I packed it all away. Last year I dug it out again and converted the locos back to analogue except for the ones that were originally digital. I put together a small layout incorporating some basic switching and automation (very basic) and run it like a train set - which is what it is. It's now fun again. I have a laugh and the interest is back where it should be - and I once again understand what every bit does and how it works. Obviously each to their own but personally I prefer the analogue operation. I suspect I'm in the minority but there you go... It also gives me an excuse to hunt for and resurrect some of the classic 'old clunkers'.
Cheers Paul
Hi Paul, thanks so much for sharing your experience, and great to hear your Marklin trainset is fun again. Very heartening that you're able to run your trains with so much enjoyment. Regards, Chris |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: hermanvk  Originally Posted by: Paul59  Obviously each to their own but personally I prefer the analogue operation. I suspect I'm in the minority but there you go...
Cheers Paul
Hi Paul, As one of the members of the minority, I can only confirm. I have only 10 locs, but all good old style analog ones, and all on M-rails! I just enjoy riding them using classic old blue transformers, and some classic automatics with relays... Minority or not, I enjoy the playing... Kind regards, Herman Hi Herman, many thanks also for sharing your enthusiasm for analogue - and I'll admit that some of the appeal in returning to Marklin after decades is nostalgia for the enjoyment of those completely analogue trains and m-rails. I am now tentatively about to experience digital too. Regards, Chris PS LPs from yesteryear are great too |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
 1 user liked this useful post by ChrisKenna
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Joined: 04/02/2021(UTC) Posts: 480 Location: USA
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Originally Posted by: hermanvk  Originally Posted by: Paul59  Obviously each to their own but personally I prefer the analogue operation. I suspect I'm in the minority but there you go...
Cheers Paul
Hi Paul, As one of the members of the minority, I can only confirm. I have only 10 locs, but all good old style analog ones, and all on M-rails! I just enjoy riding them using classic old blue transformers, and some classic automatics with relays... Minority or not, I enjoy the playing... Kind regards, Herman I converted to digital as i enjoy the tinkering part of our hobby. The wonderful clicketyclack sound of running M track is fun either way. Ben |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Originally Posted by: hxmiesa  But there is a work-around; If you can meassure the AC voltage of the reverse-pulse, and then drop it with pairs of anti-parallel diodes. Each pair will drop the voltage by about 0,7V. Have you actually tried this or is this just an idea? The voltage drop in a diode depends on the type of diode and the current. When reversing with just a decoder connected to the transformer, the current will be low and the voltage drop in the diodes may be far lower than 0.7 V. Connecting a lamp or another consumer of electric current to the transformer can ensure that the voltage is actually reduced. The diode trick works well to make locos slower, but the motor of the loco leads to a substantial current. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
 1 user liked this useful post by H0
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Joined: 14/02/2024(UTC) Posts: 59 Location: Grand-Est, Alsace
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Originally Posted by: ChrisKenna  Originally Posted by: BenP  Reversing of digital locs with older (blue) marklin transformers may damage the decoder because that voltage pulse may be 24V or more. So, only use white marklin transformer, like 6646. Hi, thanks for helpful info. Is a blue plastic Trafo 37540 (included in a starter set) seen as an older transformer, so not recommended for digital locos? - is the max voltage for reverse the issue? With thanks, Chris Hi Chris, Transformers with little power (as your 10VA transformer) often give higher tensions at low charge than do the big 30VA models. So, there is a higher risk with small transformers than with big ones. There is, also, a risk that gets higher and higher the longer you hold the inversion impulsion - good old analogicalists tend to do it longer since some relay inversers needed more time to invert correctly... On the other side, it's nonsense to pretend that white transformers are "no risk". They function on the same principe as the older models, a weak character makes that on normal charge (30VA for a 6647 or other white models) the inversion tension is 24V and the max normal tension about 16V. With low charges, the tension is higher, and there is no limitation included! So I did kill a decoder with a 6647 transformer ! Test your transformer, and do the test several times at different hours in the day, since the tension furnished by your furnisher depends on the charge, too. Some systems have lower tension on high charge, some raise the tension when charge is high, so as in winter when many people heat the house by electric radiators, or at some time on the day when many machines work in the fabrics. You have to test your secondary tension (0-B when giving inversion courant) at several times a day and on the week-end. If you are sure the tension is never above 24V, no problem. Otherwise... you better look for other solutions. Exception: old decoders with micro-switch programmation are safe to all transformers. So, I separate analogical system from all digital locos except the ones with micro-switch programmation. Digital locos on digital command, analogical locos on analogical command. That's the safest way.
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 2 users liked this useful post by Wolfram_Stn
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Joined: 23/07/2014(UTC) Posts: 8,470 Location: ENGLAND, Didcot
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Originally Posted by: Wolfram_Stn  Exception: old decoders with micro-switch programmation are safe to all transformers.
Wrong, see my post over here in answer to your incorrect statement.
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Joined: 15/11/2023(UTC) Posts: 56 Location: Alberta, Calgary
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 Originally Posted by: ChrisKenna  Hi all, probably a basic question, but will a digital loco also run on M track with an analogue transformer? Thanks for info on this. I'm returning to Marklin after decades of absence. Hello all, I don't know if this is interesting, but here is my experience - though I run only analog - and apparently those older analog locs can handle high(er) voltages. A while back I started again with these 40+ year old locs and transfos. Everything seems te work fine, the speed, the switching, and then I started measuring the voltage: I registered: Maximum on the red/brown circuit: up to 20V Switching on the red/brown circuit: up to 32.7 !!! Light circuit (yellow/brown): 30.8V So I was concerned, even for my analog locs... (imagine using a digital loc with these voltages) Viewing several optioins, I choose to use a regulator..  This allows me to regulate the voltage to my transfo's... Renewed measurements: 15.9 maximum on red/brown, 16V on the light circuit (yellow/brown), but still between 25.3 and 25.9 switching on red/brown - depending on the transfo. A long story short: measure before going into live setup. Kind Regards, Herman
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Joined: 15/12/2005(UTC) Posts: 3,590 Location: Spain
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Originally Posted by: H0  Have you actually tried this or is this just an idea? The voltage drop in a diode depends on the type of diode and the current. When reversing with just a decoder connected to the transformer, the current will be low and the voltage drop in the diodes may be far lower than 0.7 V. Connecting a lamp or another consumer of electric current to the transformer can ensure that the voltage is actually reduced. The diode trick works well to make locos slower, but the motor of the loco leads to a substantial current.
Well, yes; My whole layout is based on this system. I use the 1N4007 type diodes. (mostly) The advantage of using a diode is that it´s voltage-drop much less dependent of the current flowing, than f.x. a resistance. If you think that the voltage-drop after several pairs of diodes is not enough when sending the reverse-pulse from one of the blue Märklin trafos, then I must have been very lucky, because no deco has fried ...(*)yet! ;-) I would like to test it, though, so give me some time, and I will meassure the voltage while sending a reverse pulse, with just a single digital loco on the track. I mean; Even if the system works well in practice, a meassured voltage would be nice to back it up. (*); Actually; an older AnDi deco did die, in an Electrotren DSB Lista MZ loco that I bought second-hand. But I suspect it wasnt only because of my setup... |
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Joined: 08/11/2005(UTC) Posts: 3,528 Location: Mullerup, 4200 Slagelse
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Originally Posted by: Wolfram_Stn  On the other side, it's nonsense to pretend that white transformers are "no risk". They function on the same principe as the older models
..... So I did kill a decoder with a 6647 transformer ! Not correct, the number of windings on the secondary side are different, fewer windings on the reverse impulse part of the 6647 - but of course, if you try hard enough, even a 6647 can destroy things, however quite unusual to destroy a normal Märklin decoder. Per. |
If you can dream it, you can do it! I, the copyright holder of this work, hereby release it into the public domain. This applies worldwide. In case this is not legally possible: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.  |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Originally Posted by: hermanvk  A long story short: measure before going into live setup. That is good advice. And everybody should bear in mind that nominal voltages were increased from 110 V to 120 V on one side of the Atlantic while they went up from 220 V to 230 V on the other side of the Atlantic. That's +9% vs. +4.5%. For some areas they even went down from 240 V to 230 V. And the mains voltage is usually allowed to vary by +/- 10%. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 25/08/2012(UTC) Posts: 251 Location: South East
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That is a very good point by Tom above. Last night I measured the mains voltage where I live. It was 241 volts. So that is 4.7% higher than the nominal input voltage of my 6647 White transformers. I measured the reversing pulse with a digital locomotive on the track and it was 25.1 volts. So that is 4.5% high which is consistent with the higher input voltage.
So the output does vary slightly depending on the input voltage. It just shows that it pays to be careful even when using the white transformers. Hopefully my 25.1 volts isn't so high as to fry anything.
The mains voltage should nominally be 230 volts +10% or -6% (according to Google) so it can vary by quite a bit - mine falls within this range but it does pay to measure the voltage of the reversing pulse that is actually appearing on your track. I would hope that Märklin would have taken this variation into account when designing their circuits. |
Marklin HO using M track. Now reverted to analogue as I find it has more character and is more fun...... and I understand it! |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Originally Posted by: Paul59  Hopefully my 25.1 volts isn't so high as to fry anything. 28.28 V is the specified maximum voltage for decoders (actually it is 40 V, but 40 V DC translates as 28.28 V AC here). |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 25/08/2012(UTC) Posts: 251 Location: South East
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That's good to know Tom thanks. From what I can remember (school was a long time ago) you multiply the AC voltage by the square root of two to get the peak voltage of the sine wave.
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Marklin HO using M track. Now reverted to analogue as I find it has more character and is more fun...... and I understand it! |
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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Originally Posted by: Paul59  From what I can remember (school was a long time ago) you multiply the AC voltage by the square root of two to get the peak voltage of the sine wave.
That's it. Or the other way around: You have to divide the maximum voltage given in the decoder manual by square root of two to get the maximum your voltmeter should not exceed when testing your transformer. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
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Joined: 10/10/2024(UTC) Posts: 28 Location: NSW Australia
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Originally Posted by: Wolfram_Stn  Originally Posted by: ChrisKenna  Originally Posted by: BenP  Reversing of digital locs with older (blue) marklin transformers may damage the decoder because that voltage pulse may be 24V or more. So, only use white marklin transformer, like 6646. Hi, thanks for helpful info. Is a blue plastic Trafo 37540 (included in a starter set) seen as an older transformer, so not recommended for digital locos? - is the max voltage for reverse the issue? With thanks, Chris Hi Chris, Transformers with little power (as your 10VA transformer) often give higher tensions at low charge than do the big 30VA models. So, there is a higher risk with small transformers than with big ones. There is, also, a risk that gets higher and higher the longer you hold the inversion impulsion - good old analogicalists tend to do it longer since some relay inversers needed more time to invert correctly... On the other side, it's nonsense to pretend that white transformers are "no risk". They function on the same principe as the older models, a weak character makes that on normal charge (30VA for a 6647 or other white models) the inversion tension is 24V and the max normal tension about 16V. With low charges, the tension is higher, and there is no limitation included! So I did kill a decoder with a 6647 transformer ! Test your transformer, and do the test several times at different hours in the day, since the tension furnished by your furnisher depends on the charge, too. Some systems have lower tension on high charge, some raise the tension when charge is high, so as in winter when many people heat the house by electric radiators, or at some time on the day when many machines work in the fabrics. You have to test your secondary tension (0-B when giving inversion courant) at several times a day and on the week-end. If you are sure the tension is never above 24V, no problem. Otherwise... you better look for other solutions. Exception: old decoders with micro-switch programmation are safe to all transformers. So, I separate analogical system from all digital locos except the ones with micro-switch programmation. Digital locos on digital command, analogical locos on analogical command. That's the safest way. Many thanks for these further helpful details. Regards, Chris |
With respect and thanks to Ngannawal, Ngambri and all First Nations people |
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Joined: 15/12/2005(UTC) Posts: 3,590 Location: Spain
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Originally Posted by: hxmiesa  Originally Posted by: H0  Have you actually tried this or is this just an idea? The voltage drop in a diode depends on the type of diode and the current. When reversing with just a decoder connected to the transformer, the current will be low and the voltage drop in the diodes may be far lower than 0.7 V. Connecting a lamp or another consumer of electric current to the transformer can ensure that the voltage is actually reduced. The diode trick works well to make locos slower, but the motor of the loco leads to a substantial current.
Well, yes; My whole layout is based on this system. I use the 1N4007 type diodes. (mostly) The advantage of using a diode is that it´s voltage-drop much less dependent of the current flowing, than f.x. a resistance. If you think that the voltage-drop after several pairs of diodes is not enough when sending the reverse-pulse from one of the blue Märklin trafos, then I must have been very lucky, because no deco has fried ...(*)yet! ;-) I would like to test it, though, so give me some time, and I will meassure the voltage while sending a reverse pulse, with just a single digital loco on the track. I mean; Even if the system works well in practice, a meassured voltage would be nice to back it up. So, I was trying this out, but cant find a way to meassure it well, that would convince everybody here. My multimeter is a relatively cheap version, and it is NOT true RMS. H0 says that with just a decoder, current drop will be low; Well, with just the tester in series, the current is VERY low, and yet the drop is consistent with around 0,6Vac-0,7Vac for each diode inserted inbetween. Can somebody advise on how to test this the correct way? |
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 1 user liked this useful post by hxmiesa
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Joined: 16/02/2004(UTC) Posts: 15,443 Location: DE-NW
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I just checked the datasheet for 1n4001 diodes. The diagram starts at 10 mA and then the voltage drop is already around 0.7 V. So assuming the current drawn by a decoder is around 20 mA, it is probably safe to assume that each diode will "eat" 0.7 V. I was afraid the voltage drop would be much lower with small currents, but that is not the case here. Sorry for the confusion.
I think the "square root of two" applies here, too. I would calculate the number of diodes needed bases on the peak voltage, not the efficient voltage. |
Regards Tom --- "In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS  |
 3 users liked this useful post by H0
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Joined: 15/12/2005(UTC) Posts: 3,590 Location: Spain
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Originally Posted by: H0  I think the "square root of two" applies here, too. I would calculate the number of diodes needed bases on the peak voltage, not the efficient voltage. Maybe not; The white Märklin analogue trafos giving out 24Vac when changing direction, is referring to the effective voltage, AFAIK. Of course you could insert more anti-parallel diode links anyway, in order to get the voltage down, but in my case I am still running with many older analogue locomotives too, and I need them to be able to change direction too! ;-) BTW: The use of 1N4001 diodes; -while they may seem "enough" for our 16-24Vac trains, I have found that the bigger diodes are better, in case of short-circuits (de-railings or other metal-parts dropped on the track) The smaller diodes will die, while the bigger ones live long enough for me to fix the failure in time. Actually; I have had soldered joints break apart BEFORE the diodes died! |
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 2 users liked this useful post by hxmiesa
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