dBerriff Posted April 28 Share Posted April 28 Roads and Rails, Leeds, has made an interesting posting some 3 days ago on Facebook about (Loksound) decoder failures. The usual reason is inadvertent shorting out of the speaker supply. This blows the amplifier, not surprisingly. The classic example is the customer who joined the speaker wires to the decoder wires and then taped both direct to the metal chassis. Worth a read if you have Facebook account. Link to comment Share on other sites More sharing options...
ColinB Posted April 28 Share Posted April 28 Road and Rails are one of the good ones, another sound supplier I dealt with even when I explained my sound decoder had an issue immediately said that it was my loco that was causing the fault. I have worked in electronics for a number of years and it does go wrong, probably more reliable than many mechanical things but it still fails occasionally. Yes, shorting out any of the speaker wires will kill the decoder as it will on a car radio. Link to comment Share on other sites More sharing options...
dBerriff Posted April 28 Author Share Posted April 28 This post was prompted by some of the reports of multiple HM7000 failures. One message from the Facebook discussion is that if you do not know that you are doing something wrong then how are you going to stop doing it? Many decades ago I taught physics and our youngsters left with some concept of voltage, current and circuits. Is that no longer the case? Sorry if this is in the wrong section - I did consider putting it in General Discussion. Link to comment Share on other sites More sharing options...
SteveM6 Posted April 28 Share Posted April 28 19 minutes ago, dBerriff said: This post was prompted by some of the reports of multiple HM7000 failures. One message from the Facebook discussion is that if you do not know that you are doing something wrong then how are you going to stop doing it? Many decades ago I taught physics and our youngsters left with some concept of voltage, current and circuits. Is that no longer the case? Sorry if this is in the wrong section - I did consider putting it in General Discussion. I'm in agreement with you. I know from feedback from Hornby that the majority of decoder failures they have investigated for failure can be traced back to finger trouble from the user. Not in every case, but definitely in the majority. In my own experience of 30+ HM7K decoders there has only been one failure - it's back at Hornby Towers being investigated and I fully expect to find it was down to me. I just hope they break it to me gently. Link to comment Share on other sites More sharing options...
96RAF Posted April 28 Share Posted April 28 I have had 1 failure and that was running very hot (too hot to touch according to my IR temp gun), but the decoder still worked in a lights added Class 56. I chickened out, declared it U/S and sent it back for investigation. Never did find out if it was dodgy or if it was my loco that caused it. Link to comment Share on other sites More sharing options...
BritInVanCA Posted April 28 Share Posted April 28 (edited) I’ve had one failure. Pre installed HM7000 in a TT120 Night Hawk running on a Hornby Select powered layout. I can’t imagine what I could have done to cause a user error. It ran happily for months and then went hot and caused a short. The loco was fine on DC with a blanking plate. I have no complaints because Hornby just replaced it but they didn’t suggest what the problem might be. I agree that people should read supplied operating instructions but these are intended to be consumer level products. If you’re operating with recommended equipment any failure is the manufacturer’s responsibility Edited April 28 by BritInVanCA Link to comment Share on other sites More sharing options...
dBerriff Posted April 28 Author Share Posted April 28 No one is saying that decoders do not fail. Sometimes components are out of specification, are the wrong end of silicon yields or for whatever reason just stop working. These should be indeed replaced. Link to comment Share on other sites More sharing options...
SteveM6 Posted April 28 Share Posted April 28 Link to comment Share on other sites More sharing options...
BritInVanCA Posted April 29 Share Posted April 29 @dBerriff well actually what I sometimes see here is a tendency to assume user error as a starting point. I understand that the moderators and beta testers see a lot of user issues so it’s easy to jump to conclusions but sometimes the attitude is a little frustrating. Patience is the key for all of us. Link to comment Share on other sites More sharing options...
dBerriff Posted April 29 Author Share Posted April 29 (edited) The Facebook discussion shows that is it not just Hornby decoders that fail. The HM7000 range is probably no better or worse in that respect as the different makers' boards will be using components from the same sources. Assembly will be by robot. The variables are chance and the installation procedures. Another message from the discussion is that buying from a dealer and paying them to do the installation eliminates the element of chance as the install will be tested and medium term failure will be covered by consumer law. Edited April 29 by dBerriff Link to comment Share on other sites More sharing options...
SteveM6 Posted April 29 Share Posted April 29 7 hours ago, BritInVanCA said: @dBerriff well actually what I sometimes see here is a tendency to assume user error as a starting point. I understand that the moderators and beta testers see a lot of user issues so it’s easy to jump to conclusions but sometimes the attitude is a little frustrating. Patience is the key for all of us. It works the other way as well. Plenty of instances where the user's default position is to immediately blame Hornby. "A bad workman etc" Reality is likely somewhere in-between. 1 Link to comment Share on other sites More sharing options...
dBerriff Posted April 29 Author Share Posted April 29 I have been as diplomatic as I know how to be and evidence-based insofar as that is possible. Link to comment Share on other sites More sharing options...
96RAF Posted April 29 Share Posted April 29 Standard fault diagnosis is to determine the root cause of failure, first to see if the unit has failed and if so why, hence rule out finger trouble, especially incorrect power source due to misleading initial advice from Hornby at shows. That advice quickly rescinded in light of user feedback. Next is to rule out the loco and the installation, then it is back to the decoder and the bathtub reliability curve. Link to comment Share on other sites More sharing options...
ColinB Posted April 29 Share Posted April 29 14 hours ago, SteveM6 said: Yes, the good old bathtub curve. In my experience one of the big cause of failures is overheating so covering them in shrink rate is a no. I did have one fail, which I definitely couldn't explain. I had lots of TTS just die, I haven't got enough HM7000 to comment. Trouble is a lot of people that probably use them don't use this Forum. Link to comment Share on other sites More sharing options...
SteveM6 Posted April 29 Share Posted April 29 The heatshrink issue is, in my experience, unproven. For a start many aftermarket decoders I've used are wrapped from the factory and I've not had an issue. Equally, I've routinely wrapped TTS and TXS with no issues (yet). I admit that my locos are not submitted to extended operating sessions although they spend hours sitting on a 'live' layout with the sound on. I do use a very thin, clear heatshrink, so maybe that helps. Link to comment Share on other sites More sharing options...
96RAF Posted April 29 Share Posted April 29 Exception to the norm - I have had a TTS decoder close wrapped in regular heat shrink in an enclosed coal bunker for years. It doesn't often run for long but it is on track all the time. Link to comment Share on other sites More sharing options...
ColinB Posted April 30 Share Posted April 30 On 29/04/2024 at 13:03, SteveM6 said: The heatshrink issue is, in my experience, unproven. For a start many aftermarket decoders I've used are wrapped from the factory and I've not had an issue. Equally, I've routinely wrapped TTS and TXS with no issues (yet). I admit that my locos are not submitted to extended operating sessions although they spend hours sitting on a 'live' layout with the sound on. I do use a very thin, clear heatshrink, so maybe that helps. I was talking to my Zimo decoder supplier and they were saying on some of the newer decoders that don't shrink wrap them, these being the smaller ones. Most electronics needs a way to dissipate the heat so tightly wrapping them in heat shrink is not going to be a good idea, especially if they are the small variety. It is what you are happy with. I tend to insulate where they are being fitted, most times it only needs to be on one side and if it is an 8 pin variety the PCB side with the hot components uppermost. Link to comment Share on other sites More sharing options...
RB51 Posted April 30 Share Posted April 30 Kapton tape. R- Link to comment Share on other sites More sharing options...
dBerriff Posted April 30 Author Share Posted April 30 Audio amplifiers add to heat generation. Hornby set default volumes surprisingly high when they first released the HM7000 range. I find a setting of 15 to 25 is about right. After that you just increase distortion and eventually start damaging the speaker coil as it overheats. Insulation melts, resistance drops, current increases further and the result is a blown amp. This is will happen to all makes, not just Hornby/HM. I presume it is just not possible to include over-current protection on these tiny boards. Link to comment Share on other sites More sharing options...
ColinB Posted April 30 Share Posted April 30 4 minutes ago, dBerriff said: Audio amplifiers add to heat generation. Hornby set default volumes surprisingly high when they first released the HM7000 range. I find a setting of 15 to 25 is about right. After that you just increase distortion and eventually start damaging the speaker coil as it overheats. Insulation melts, resistance drops, current increases further and the result is a blown amp. This is will happen to all makes, not just Hornby/HM. I presume it is just not possible to include over-current protection on these tiny boards. I don't think Hornby has any, Zimo has a little but it is only good for a short period. Link to comment Share on other sites More sharing options...
96RAF Posted April 30 Share Posted April 30 Over-current is only provided for motor control, not function output or audio amp. Link to comment Share on other sites More sharing options...
dBerriff Posted May 1 Author Share Posted May 1 Thank you for the information. The referenced supplier mentions ESU boards being blown. Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now