norman Posted November 16, 2016 Share Posted November 16, 2016 The bottom view of the MX644D shown in the Zimo User Manual looks a little different to the one I have just bought. Please see file attached. Are these the correct pads for attaching a capacitor? Zimo MX644D Bottom View.PDF Link to post Share on other sites More sharing options...
Suzie Posted November 16, 2016 Share Posted November 16, 2016 Hi Norman Looking at page 9 of the manual:- http://www.zimo.at/web2010/documents/MX-KleineDecoder_E.pdf ... suggests that the capacitor should be connected to the loco board. Only solder to the decoder as a last resort. Link to post Share on other sites More sharing options...
norman Posted November 16, 2016 Author Share Posted November 16, 2016 Hi Norman Looking at page 9 of the manual:- http://www.zimo.at/web2010/documents/MX-KleineDecoder_E.pdf ... suggests that the capacitor should be connected to the loco board. Only solder to the decoder as a last resort. Hi Suzie On page 9 it says "if not mounted on loco board and connected via plug" and there are two solder pads provided. As far as I can see there are no connections for a capacitor on the loco board (Dapol 08) so that's not possible. Also, the capacitor for the 644 is shown as being connected via the solder pads Norman Link to post Share on other sites More sharing options...
Suzie Posted November 16, 2016 Share Posted November 16, 2016 Hi Suzie On page 9 it says "if not mounted on loco board and connected via plug" and there are two solder pads provided. As far as I can see there are no connections for a capacitor on the loco board (Dapol 08) so that's not possible. Also, the capacitor for the 644 is shown as being connected via the solder pads Norman Hi Norman The decoder offers both methods, but if there is no facility on the loco PCB you have no choice but to solder it to the decoder. The whole idea of the decoder sockets with lots of pins (MTC-21 or PluX) is that you don't have to solder anything at all to the decoder - all the connections should be to the PCB in the loco! I suspect the pads are only there as an artifact in case they decided to make a MX644, MX644L or MX644R version. It is a strange omission by Dapol to not have a stay alive facility on the PCB when their factory fit decoder is a Zimo that will have the facility for stay alive. Link to post Share on other sites More sharing options...
pauliebanger Posted November 17, 2016 Share Posted November 17, 2016 Norman, Yes, these are the correct pads and you have identified the correct polarity. Some issues arising. 1 ) Do not solder the 'legs' of any capacitor directly to the pads. The stiffish metal can put too much mechanical stress on the pads and lift them off the decoder. Pre-tin the pads and connect the cap(s) with wires. Remember to insulate any bare metal. 2 ) The MX644D has a cap charging circuit but does not regulate the voltage supplied to the cap. Ensure that the voltage rating of the caps you use comfortably exceed the highest voltage you are likely to have on your tracks Kind regards, Paul Link to post Share on other sites More sharing options...
pauliebanger Posted November 17, 2016 Share Posted November 17, 2016 Hi Norman The decoder offers both methods, but if there is no facility on the loco PCB you have no choice but to solder it to the decoder. The whole idea of the decoder sockets with lots of pins (MTC-21 or PluX) is that you don't have to solder anything at all to the decoder - all the connections should be to the PCB in the loco! I suspect the pads are only there as an artifact in case they decided to make a MX644, MX644L or MX644R version. It is a strange omission by Dapol to not have a stay alive facility on the PCB when their factory fit decoder is a Zimo that will have the facility for stay alive. Suzie, I entirely agree with what you say except for your comment on the 'missing' Stay Alive connections. In my experience, far from being usual that manufacturers provide accessible connections on the loco PCBs unless the model as sold requires, it the usual practice is to ignore any connections above the minimum required to operate the model and any fitted lights. Speaker connections are the possible exception to this general rule. Things are improving, and lobbying helps to keep up the pressure on manufacturers. I know of only two manufacturers who have a policy of providing accessible connections for ALL pin positions on their loco PCBs, Suttons Locomotive Workshop and the Little Loco Company. The fact that these manufacturers have been far sighted enough to eschew the 'obsolete since 2009' 21 pin MTC connection in favour of PluX connections also demontrates their desire to make all the decoder's features readily and easilly available to anyone. This has been largely acedemic to most users, since if the loco and lights work according to spec, these 'shortcomings' are never manifest. Only those reqiring acees to power addition features would normally be aware. The irony is that a loco PCB with all 21 pins having a trace and an accessible solder pad/connector provided is virtually no more expensive to produce than one which has nothing more than the basics on board. It just needs the modeller's needs to be taken into account at the design stage. Lets hope others follow suit. (And I am very hopeful that at least one of or major manufacturers is taking note of this). Kind regards Paul Link to post Share on other sites More sharing options...
norman Posted November 17, 2016 Author Share Posted November 17, 2016 Norman, Yes, these are the correct pads and you have identified the correct polarity. Some issues arising. 1 ) Do not solder the 'legs' of any capacitor directly to the pads. The stiffish metal can put too much mechanical stress on the pads and lift them off the decoder. Pre-tin the pads and connect the cap(s) with wires. Remember to insulate any bare metal. 2 ) The MX644D has a cap charging circuit but does not regulate the voltage supplied to the cap. Ensure that the voltage rating of the caps you use comfortably exceed the highest voltage you are likely to have on your tracks Kind regards, Paul Hi Paul Thanks for the answer to my question. I just wonder why the Zimo manual does not show the same view as the decoder I just purchased, in truth it does not even show the solder pad for the cap Neg - you just have to imagine it. Marks out of 10 <5. Further more the Zimo manual says 35 volt for the capacitor but packaged with the decoder wa a "free" 25 volt capacitor. Very stange! I understand your comment about higher than the track voltage. Many thanks Norman Link to post Share on other sites More sharing options...
pauliebanger Posted November 17, 2016 Share Posted November 17, 2016 Nor Hi Paul Thanks for the answer to my question. I just wonder why the Zimo manual does not show the same view as the decoder I just purchased, in truth it does not even show the solder pad for the cap Neg - you just have to imagine it. Marks out of 10 <5. Further more the Zimo manual says 35 volt for the capacitor but packaged with the decoder wa a "free" 25 volt capacitor. Very stange! I understand your comment about higher than the track voltage. Many thanks Norman Norman, On the contrary, the picture in the manual Page 9, and the colour one on the inside of the card insert both clearly show these pads and their polarity. For normal DCC (14 - 16v) a 25v cap gives a reasonable headroom. If your system is properly regulated, 16v caps will be OK. Manufacturers often overstate the requirements to build in a greater safety margin since not all users will be as knowledable. Better safe than sorry. (unfortunately, higher voltage caps are physically larger so finding space may be more difficult in some models). Kind regards, Paul Link to post Share on other sites More sharing options...
norman Posted November 17, 2016 Author Share Posted November 17, 2016 Nor Norman, On the contrary, the picture in the manual Page 9, and the colour one on the inside of the card insert both clearly show these pads and their polarity. For normal DCC (14 - 16v) a 25v cap gives a reasonable headroom. If your system is properly regulated, 16v caps will be OK. Manufacturers often overstate the requirements to build in a greater safety margin since not all users will be as knowledable. Better safe than sorry. (unfortunately, higher voltage caps are physically larger so finding space may be more difficult in some models). Kind regards, Paul Hi Paul I am looking at page 9 as I type - it only shows the solder pad for the CAP pos. The CAP neg wire changes to dotted but does not terminate at a pad and in any case the picture on page 9 is significantly different to the decoder I have - please see the photo on my first posting, hence the original question. However, that said the picture shown inside the card packaging is correct in both orientation of all the components and the 25v.- I just did not know that existed until you pointed it out. Thanks. Yes, I understand about the voltage but it is inconsistent and confusing when the Zimo manual says 35v and a 25v is included with the decoder. Norman Link to post Share on other sites More sharing options...
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