Accessory Decoder [R8247 Port 1 sparks when connecting wire]

[Chrissaf]

I've programmed my R8247 accessory decoder with address 61 to 64. When nothing is connected to port 61 the other three ports work perfectly. When I put a point motor on 61 then nothing works. If I disconnect the red wire on 61, the other three port work correctly. It makes no difference if the point motors are on the track or not.

I have noticed that when I connect the red wire to port 61 there is a small spark, and maybe a movement on that point motor. It is possible that with only the green wire connected the point on port 61 operates correctly in one direction.

Can anybody help please?

[Chrissaf]

Disconnect the wiring from Port 2 [62].

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Now try connecting the wires you want to put on Port 1 [61] on Port 2 [62] instead.

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Does the fault now return that makes all ports non functional.

If it does, then there is a fault in the wiring or the point motor.

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If the points on Port 2 now works fine as well as those still on Ports 3 & 4

Then the R8247 Accessory decoder is likely to have an issue on Port 1.

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The addresses used i.e 61 to 64 are immaterial and have no bearing on this issue. It is a physical electrical issue.

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I suspect that my diagnostic test procedure above will prove the issue to be with Port 1 on the R8247.

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Just considering that port in isolation for a moment.

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The red wire would typically be connected to the + terminal on that port if using normal Hornby wiring convention. The black wire on the C terminal and the green wire on the - terminal.

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The C terminal is always permanently 'on' (live) with a positive voltage.

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The terminals marked + & - are normally floating (have no specific voltage polarity) and are switched negative with a brief 100 millisecond pulse when the port is enabled to operate a point.

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Now assuming that your red wire is indeed connected to the + terminal. For you to observe a spark, then that + terminal must be enabled and in its 'switched negative' state.

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A point motor has an extremely low impedance and for all intent and purpose looks like a 'short circuit' to the R8247 port. This would prevent the other ports on the R8247 from operating as you have observed.

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Now the question is why does the + terminal (or - terminal if wired opposite to convention) have a permanent negative voltage on it.

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One answer is that it has a fault on it and the output FET semi-conductor used to switch the voltage has failed and gone short circuit. This is a possibility.

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Another possible reason is that through a programming error you have accidentally configured Port 1 on the R8247 to be configured for 'Always On' operation. Or if it was a second-hand purchase, the previous owner had it configured that way.

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You haven't told us what DCC Controller you are using, but the fact that you are configuring DCC addresses 61 to 64 infers that your controller is a Hornby Select.

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From what I can see documented in the R8247 manual, the Select prior to firmware revision 1.6 does not have support for changing CV515/CV3 in the R8247. These CVs control the Port 1 output status and configure 'always on' or 'pulsed' operation. Pulsed is the factory default.

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If you purchased the R8247 brand new in a sealed package, then the likely-hood is that the R8247 Port 1 semi-conductor output has a fault (because the factory default is 'pulsed' operation and not 'always on') and the R8247 should be returned for warranty replacement where you purchased it from.

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If it was purchased second hand, then it may be (no guarantee, as it could still be a fault) that it just needs the port to be reconfigured for pulse operation if it is assumed that the previous owner configured Port 1 for 'always on'. But as just said, this looks like it cannot be done with the basic Select unless the firmware is version 1.6

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To identify the installed firmware, watch the LCD screen as you power up the Select. Three numbers are displayed sequentially:

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nn followed by 30 followed by 03 where nn is the firmware version. 11 would be version 1.1.......15 would be version 1.5 etc.

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You can send the Select back to Hornby and have the firmware upgraded to version 1.6 for a one off fee of £15 plus postage costs. Version 1.6 will add the ability to write to all the decoder CV including CV515/CV3 and also CV8 to perform a factory reset. You need a 'returns number' allocated by 'Hornby Customer Care' for this - see the 'Contact Us' link at the very bottom of the page.

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You could alternatively write a value of 8 to CV8 and this will revert the R8247 to factory configuration (all ports pulsed). However this will also revert the port addresses 61 - 64 to 1 - 4. So the port addresses will need to be reconfigured as well.

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If you don't have a Select but another controller or even a non Hornby branded one, You just need a controller that can write to any CV.

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LAST MINUTE EDIT:

Since you say that if you leave the red wire disconnected and just have the green and black wires connected, the point operates but only in the green direction. Then that would indicate that the red wire terminal is more likely to have a semi-conductor short circuit fault. The reason I say this is because if the issue was a configuration one, such that Port 1 was configured for 'Always On' then the green wire terminal would also be 'Always On' when the port was switched to that terminal. So if the other ports still continue to work with the green and black wires attached and at the same time that the green terminal is enabled as well, then a port output semi-conductor fault is the more likely scenario. Note that 'Always On' configurations default to the + terminal being energised by default when the R8247 is first powered up, rather than the - terminal. When you switch the port, the 'Always On' voltage is a toggle between the + & - terminals. Both + & - terminals are never both 'Always On' together. Unless, of course, a port output semi-conductor fault is present.

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TIP: As a newbie poster on the forum, just be aware that the 'Blue Button with the White Arrow' is not a 'Reply to this post' button. If you want to reply to any of the posts, scroll down and write your reply in the reply text box at the bottom of the page and click the Green 'Reply' button.

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See also – further TIPs on how to get the best user experience from this forum.

https://www.hornby.com/uk-en/forum/tips-on-using-the-forum/

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[jane1707819582]

Swap over two point motors does the same happen ?. If so this suggests the decoder may be faulty . the whatever that pulses the current maybe faulty .

[ADC aaaaaaaaaaa]

A bit more information ......

when I connect the red +ve wire to the decoder it actives the point motor without any commands being entered on the controller, and stops all other ports working. Removing the red wire reactivates the other three ports, and allows port 61 to operate in the other direction (I think).

[Chrissaf]

I have incorporated your 'bit more information' into my first reply as an edit.

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What you describe is in line with what I would expect to observe in the two possible scenarios I have documented in my reply.

[96RAF]

Go here, . .

http://www.halton96th.org.uk/page16.html

Scroll down to known faults. Sounds very much like your scenario.

 

The reason you see sparking is because the port is effectively always on (pulsing rapidly). As stated with a point motor attached it drains the internal CDU but without a point motor attached the internal CDU recharges to give a spark when you touch wires.

[ADC aaaaaaaaaaa]

Thanks everyone, problem sorted. Inspired by what you said above, I replaced the decoder with a different one, and still had the same problem. So not a decoder problem. So I connected the original decoder directly to the Select controller, with a point motor on port 1, and it worked. I gradually added motors to the other ports and all worked well. So I disconnected all relevant track wiring and started again. This time activating one port at a time, and all is now working. So it looks like a had a wiring issue, although I never found one. Thanks for you replies.

[Chrissaf]

Thank you for the update.....Rob might have more to add regarding his suggested Select firmware fault when he sees your reply, now that you have confirmed you are using a Select.

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Can you please confirm what firmware revision your Select is running?

[see my original reply for how to identify the firmware version]

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If it is the buggy 1.1 version, it is still extremely worthwhile getting it updated by Hornby. Apart from the enhanced CV writing capability of the current 1.6 version. Version 1.1 is very old and has other issues you have just not found yet.

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[ADC aaaaaaaaaaa]

Your suspicionS are correct, I'm on 1.1

[Chrissaf]

I feel you would be wise to heed Rob's comment in his posted link about the effect of the Select 1.1 firmware bug on the operation of the R8247. It is possible that your methodical approach to 'one port at a time' connections might only be a temporary fix. The benefits that you will get from upgrading the Select to 1.6 firmware are well worth the £15 plus postage fee.

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Rob can quote you 'chapter and verse' on the new features in 1.6 and prior versions. He has done a lot of Select testing using this latest 1.6 firmware version.

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For example..... apart from the fact that version 1.6 allows you to use a Select to write to all the decoders CVs. Version 1.6 also gives full support for the Hornby TTS sound decoders. When Hornby return a Select that has been upgraded to 1.6 they include an addendum document to the user manual as the 'user interface' using 1.6 is significantly different in certain areas.

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[96RAF]

I would not use any acc decoders with your Select until you get it updated. By substituting decoders you will have stressed that one as well.

 

In fact I would tell HCC about the fault when you contact them about the upgrade as they may replace the acc decoders which have been stressed by the Select bug and update your Select f.o.c.

 

Read my teardown report again carefully so you can talk to them with authority about the bug and the ongoing fault.

 

Select upgrade benefits see here...

Version 1.0 - Initial release. Point and accessory addresses start at 60 in order to use all groups of four up to last address 99. Able to control functions 0-4.

 

Version 1.1 - Point and accessory addresses now start at 61 through 99 to accord with NMRA addressing groups. Users upgrading from v1.0 should readdress all their points and accessory addresses to the new system. Able to control functions 0-8. Able to program on the main (POM).

 

Version 1.2 - Start up screen shows revision state. Improved throttle interface. Changes to setting up default direction switching. Resume operations after a power down/restart.

 

Version 1.3 - Programming improved for ESU Loksound v4.0 sound decoders.

 

Version 1.4 - Minor update to correct function control issues.

 

Version 1.5 - Major system upgrade to extend function range 0-28 in support of sound decoders. Change to function methodology.

 

Version 1.6 - Major system update to allow CV’s to be changed and provide improved overload protection.

 

 

[ADC aaaaaaaaaaa]

Exactly one week and one working day later, my controllers have been returned from Hornby with version 1.6 loaded. Excellent service, and as you said, they included a printed addend detailing the changes to the manual. A quick test and all point motors work correctly. I'll set about programming the next decoder soon.

Thank you all for your help.

[96RAF]

Thanks for the feedback.