idlemarvel Posted August 31, 2014 Share Posted August 31, 2014 I have 3 x R8247 which I use with eLink and Railmaster. They have all worked fine until recently. Now one of them has a problem with port 2, in that the + lead is permanently on, whatever signal is sent to that port. The other ports work fine. I have reset the decoder (setting CV8 to 8) and reprogrammed it but still the same. I guess it is a hardware problem, maybe an internal short? The device is well out of any warranty so I might have a go at looking inside. Before I do has anyone else got any advice or experience to offer? Thanks. Link to comment Share on other sites More sharing options...
cliveg Posted August 31, 2014 Share Posted August 31, 2014 Just checking the obvious, what does Railmaster show in the Accessory Decoder setup for the Always on (lights) setting for this particular port on the "faulty" decoder? Link to comment Share on other sites More sharing options...
gilbo2 Posted August 31, 2014 Share Posted August 31, 2014 Not looking good, I've not had this one. I would just check that CV3 to CV6 are all at 1, but setting Cv8 to 8 should have done that, worth checking though. Otherwise it sounds like a replacements needed as I would be surprised if there is anything serviceable on the inside but you live and learn. Link to comment Share on other sites More sharing options...
idlemarvel Posted August 31, 2014 Author Share Posted August 31, 2014 Thanks Clive but all ports are programmed to 100ms burst Link to comment Share on other sites More sharing options...
idlemarvel Posted August 31, 2014 Author Share Posted August 31, 2014 I will check cv3-6 but as you say resetting and reprogramming should have done that. I'll take a look inside and report back. Link to comment Share on other sites More sharing options...
Graskie Posted August 31, 2014 Share Posted August 31, 2014 Just a thought, probably not at all helpful, but have you tried disconnecting the offending wire from the decoder and then reconnectiong it? I don't really know how the connections work, not having used an auxilliary decoder yet, but I have had experience of other items such point lever switches not operating properly because of a wire inserted just a bit too far. Link to comment Share on other sites More sharing options...
idlemarvel Posted August 31, 2014 Author Share Posted August 31, 2014 Thanks Graskie, but I have tried it with no wires in, just measuring with a voltmeter, so I don't think that's the issue. Link to comment Share on other sites More sharing options...
St1ngr4y Posted August 31, 2014 Share Posted August 31, 2014 I think some sort of internal short is more likely. Could it be that a thin strand of wire has broken away from the incoming lead inside the screw connector and caused a short? Maybe disconnect all wires, open all screwconnectors then gently tap the decoder to see if any loose thread of wire drops out.Ray Link to comment Share on other sites More sharing options...
gilbo2 Posted August 31, 2014 Share Posted August 31, 2014 Managed to find a couple of R8217 PCB photos, might be repairable if you have got some good desoldering equipment?; (Dont know how different the R8247 board is though)...http://tinyurl.com/nke9z3jhttp://tinyurl.com/olep7tz Link to comment Share on other sites More sharing options...
idlemarvel Posted August 31, 2014 Author Share Posted August 31, 2014 Thanks all for the suggestions, they will help a lot. Link to comment Share on other sites More sharing options...
Fishmanoz Posted August 31, 2014 Share Posted August 31, 2014 Might be worth asking HCC if these are generally repairable, noting that it was a high level of faults in these that preceded them going off the market more than 12 months ago. I'm going to have to face this myself sometime soon, my layout development plans have been on hold and I have a number of 8247s I bought some time ago and yet to find out if they work. Link to comment Share on other sites More sharing options...
idlemarvel Posted September 1, 2014 Author Share Posted September 1, 2014 So I took my R8247 apart. The rubber feet cover the 4 screw holes, they use triangular screw heads but a suitable size flathead screwdriver can undo them. Inside it is just one PCB with 4 x large 4700 microFarad capacitors (individual CDUs) and 2 large resistors, and on the other side an array of transistors, pretty much as in the pictures posted earlier. For completeness, the PCB has printed AccessoryDecoder V3.2 on one side and a white stuck on label with SDK4810 on the other. The box cover has 49/10 embossed on the base.I could not see anything wrong visually, no loose connections, no stray wires, so it must be a blown circuit, either the swtiching transistor or the IC that controls that port. The code on the IC is ZXMN3A06D (made by Zetec). To double check I reset the decoder again and read back the CVs 3-6 (all set to 1), but port 2 is still giving constant (7v) on the negative side (I incorrectly said the + side in my first post). The + side of port 2 works properly, and ports 1, 3 and 4 work properly as well. I think I will have to live with it.Fishy, I did contact HCC who said I could send it in and they would take a look at it, but I'm not convinced they would start trying to fix a PCB, for the sake of the cost of a new board it wouldn't be worth it. Hey ho. Link to comment Share on other sites More sharing options...
idlemarvel Posted September 1, 2014 Author Share Posted September 1, 2014 Nearly but not quite the same, magfan. For example mine has 2 large resistors on the back instead of just one. Reverse side has similar looking IC components but laid out and labelled differently. Those pictures are of an R8216 (not 8217) which did not have programmable pulse times or the option for continuous output, which I guess called for some redesign. Link to comment Share on other sites More sharing options...
Fishmanoz Posted September 1, 2014 Share Posted September 1, 2014 Just a reminder here that these items were clearly quite fault-prone, so failure rate was high, even in correct operation. Whether it was due to design, manufacture or faulty components we have no idea. However, as I'm sure many must have come back under warranty, being more insistent with HCC to tell you if there were any common faults to look for may be useful. If it's the control IC, you probably have little hope of fixing it. If it's an output transistor or a diode as magfan suggests above, repair is a real possibility. In fact, testing a diode is just a matter of seeing if it shows high resistance on your multimeter with leads one way around and low resistance with them the other. Link to comment Share on other sites More sharing options...
idlemarvel Posted September 2, 2014 Author Share Posted September 2, 2014 Thanks for all the input. On the warranty question I have had many years of productive use of this device, the fact that one half of one port has now stopped working is something I'm prepared to accept as normal wear and tear. I am one of those railway modellers who is forever rebuilding their layout, including rewiring, so it's not as though these devices have been installed once and left to run . I probably have the electrical competence to test and install a new diode, if that is what the problem is, but the chance of buggering up the rest of it exists which given there is still no supply of new R8247s is not something I want to risk. Thanks again everyone but I'm not going to take any more action (unless another port goes!) :-) Link to comment Share on other sites More sharing options...
gilbo2 Posted September 2, 2014 Share Posted September 2, 2014 It will be interesting to see if the new R8247's change in any way. Time will tell..... Link to comment Share on other sites More sharing options...
idlemarvel Posted September 2, 2014 Author Share Posted September 2, 2014 So, as a final chapter on this, I have got the faulty port to operate a colour signal by setting the port to constant output instead of pulsed and using the working half of the port to trigger a relay (SPDT non-latching) to switch the signal. I used the non-working half of the port as a useful 9v DC output to power the LEDs in the signal. So it now operates through RM as if nothing had happened! I'll put the (simple) circuit diagram on dropbox later with a link in this thread in case anyone else has this or a similar problem. Cheers Dave Link to comment Share on other sites More sharing options...
gilbo2 Posted September 2, 2014 Share Posted September 2, 2014 Clever idea, be interested in our link when ready. Link to comment Share on other sites More sharing options...
idlemarvel Posted September 2, 2014 Author Share Posted September 2, 2014 Circuit diagram https://www.dropbox.com/s/lutjftrrxawg99q/relay.pdf?dl=0 Link to comment Share on other sites More sharing options...
gilbo2 Posted September 2, 2014 Share Posted September 2, 2014 Smart diagram and smart little circuit, must keep for reference. Thanks Link to comment Share on other sites More sharing options...
Fishmanoz Posted September 2, 2014 Share Posted September 2, 2014 I wonder if Hornby have a heap of "faulty" stock that could be put to this use? Link to comment Share on other sites More sharing options...
Pete172 Posted September 2, 2014 Share Posted September 2, 2014 Hi , I'm slightly concerned with this thread, as I have spent about £170 on R8247 decoders. I am still building my layout so the decoders have only been used for testing purposes, one of these decoders failed a while ago but luck allowed my model shop to replace it (but they have recently closed for business unfortunately).I am worried that some of my other decoders may fail in future, especially if the R8247 has a bad reliability record..Also, my Elite (hardly used) refused to boot up a while ago, this required a return to Hornby, who thankfully got it working again.Between the decoders and Elite alone, I have spent circa £350, so I expect the equipment to be reliable. If another piece of this equipment fails, then I will seriously consider changing my DCC system to another make.N.B. If Hornby know that the R8247 is defective, why don't they offer a replacement for the new model when it is available ? Link to comment Share on other sites More sharing options...
gilbo2 Posted September 3, 2014 Share Posted September 3, 2014 I started off with 7 R8247's and over a period over 12 months, 4 have failed and had to be replaced. However, in my case the failure mode is not as per this thread, i.e. they failed as I could no longer read or change CV values, in other words they were completely dead.Thankfully the Hornby returns process is really good and they just replaced them. The problem is though, last I heard, is they have no more warranty stock for returns either.My other observation with them is that they have a higher tendency than I would like to reset themselves after a short circuit, i.e. CV's resetting to 000. They can be recovered though from this but its a pain having to connect to the programming track each time. HOWEVER, this problem was reduced significantly by good bus design. e.g. I improved my wiring by fitting bus suppressors and putting all the R8247's on their own mini "ring bus".I still have one that is more sensitive than all the others to resetting. Currently I have relocated it to a completely different section of the bus and its been fine for the last 2 months. What's the phrase, walking on egg shells?!To complete my “story” I did replace two R8247's with the Tawcrafts PAD. These have never once “hiccuped” in terms of resets and having a separate 19V DC supply, point operation is really confident and strong. (You can probably guess what I would do if I could go back in time).Finally, whilst I'm waffling, due to the programs I write, I have quite literally switched 1000's of points now. Not once have I benefited from the “double pulse” that Railmaster does when switching points. In fact, after the first pulse, the CDU does not recharge fast enough to operate anything on the second pulse anyway (default points timer though). My suggestion to HRMS would be to have the option to disable double pulses? (If you have 2 points on the same decoder output, Railmaster even sends 3(!) pulses, again the CDU does not recharge fast enough). Now I know I could increase the point timer but my “point” is that the second pulse has never once actually helped me and I'd love to disable it. Writing my own programs does overcome all this though as this will only send a single pulse.So in summary, if you already have them, Hornby do offer good warranty support if needed and with some of the tips above you can get them to work really well.done! Link to comment Share on other sites More sharing options...
gilbo2 Posted September 3, 2014 Share Posted September 3, 2014 My own post got me thinking, what if I reduce the point timer? So I changed it to 0.05 and that's effectively "masked" the double pulse. For me I much prefer this. (This is not recommend though if you allow Railmaster to "set points" at start up.) You have to remember though to allow the CDU to recharge before clicking on another point. My suggestion will not help everyone but allows slicker operation for me, especially with those "other" PAD's ;-) Time to go out................ Link to comment Share on other sites More sharing options...
idlemarvel Posted September 3, 2014 Author Share Posted September 3, 2014 Just to say that I have 3 x R8247 and they have worked fine for the last few years, with the recent exception detailed in this thread. I have not had the need to try others as my various layouts have never needed more than 12 points.@dgilbert2 I agree about the "double pulsing" it is fairly useless unless you set the delay time to 2 or 3 seconds to give the CDU enough time to recharge. Like you I use programs to only fire points once.@HRMSYou should make this double-pulse a set-able option in the ini file in the next release Link to comment Share on other sites More sharing options...
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