Point Decoder.

[Chrissaf]

After a short circuit on my track my point decoders only part worked. Resetting the addresses made no difference. Anybody else had the same problem?

[Chrissaf]

Anybody else had the same problem?

.

If it is a Hornby R8247 Accessory Decoder, then yes, just about everybody. It is a very well known and documented issue covered many times in other various posts and threads.

.

The following is based upon my own personal experience.

.

These R8247 decoders are prone to corruption or permanent damage when 'short circuits' occur on the track or elsewhere in the DCC signal path.

.

Varying degrees of corruption / damage can occur.

.

Sometimes, the decoder just reverts back to the factory default configuration which is DCC Addresses 1 to 4. This can usually be recovered by just re-addressing the decoder to your preferred addresses.

.

Sometimes, the decoder has its configuration significantly corrupted. This usually shows up when you read the decoder addresses as -3 to 0 (obviously a minus address is totally invalid). This is what my 'short circuit' damaged decoder showed after reading the addresses. I found that just re-addressing the decoder, was not effective. In order to recover, I had to write 8 to CV8 to perform a full factory reset, before I could re-instate my original working DCC addresses.

.

However, I also found that the decoder had now become sensitive to any further 'short circuits' no matter how slight and would reset again back to these odd -3 to 0 address range. I was having to reset the decoder almost weekly. So I ended up replacing the decoder with a new one.

.

In order to protect both the new replacement and my other R8247s against this happening again, I fitted a home made 'Snubber' which is a simple capacitor / resistor filter circuit near to where my R8247s connected to my DCC signal supply. Since fitting my 'Snubber' my remaining R8247s have been completely oblivious to any track or other short circuits. I highly recommend that you protect your decoders, once fixed, with one of these 'Snubbers'.

.

Now comes the crux question. What controller are you using? If you are using a Hornby Select, then you will not be able to write 8 to CV8 to perform a factory default reset. The Elite will easily write 8 to CV8 on the R8247. RailMaster can be used to perform the same, but you use the loco CV screen and NOT the Accessory Decoder screen to do it. Note that whatever CV reading / writing capable controller you use, the R8247 must be disconnected from the layout and connected directly to the controller programming output.

.

If you have a Select, and therefore can't write 8 to CV8 then you are up the creek without a paddle. If your controller can write 8 to CV8 and doing so provides NO improvement, then the R8247 is more than likely permanently damaged beyond repair.

.

Here are some clickable information resources for further reading relating to what I have written above:

Snubber theory.

Using RM to reset a R8247 Accessory Decoder - fourth post down on the page

[96RAF]

“...up the creek without a paddle...”

 

The only option if using a Select at present is to re-address the points decoder as per the manual, noting the Select address range limitation for points and as Chris states with only that device connected to the controller programming output (Select has a common Track/Prog output).

Rob

[Fishmanoz]

I’m being somewhat cynical and tongue in cheek here but let me repeat advice I’ve given many times before concerning your Select - disconnect and remove it from your layout and place it in your bottom drawer, then buy a real controller like Elite. If the Select had been heavier it would have been much more useful - as a doorstop.

 

Moving right along - my advice on your 8247s - remove them from your layout and place them next to your Select. Buy real ones. Don’t waste gaffer tape joining the Select and one or more 8247s together, they are still too light, and now too bulky, to be used as a doorstop.

 

Finally, shut your bottom drawer, you won’t be needing to open it again. Most of the rest of your Hornby kit is actually fit for purpose. 

[Chrissaf]

Edward, having just looked at your posting history. This issue seems to possibly be a continuation of the issue you raised in July. At that time you stated that you had a Select controller.....is that still the case?

.

For others reading, see July post on link below:

https://www.hornby.com/uk-en/forum/faulty-point-decoders-19577/?p=1/#post-216270

.

The replies and advice given then, is pretty much the same as the advice given above in response to this new post.

.

The July thread was just left 'high and dry' without any feedback from yourself. For example, did the July suggestion to factory reset the Select, provide a fix?

.

If you don't enter into some 'two way' dialogue with us, this issue is likely to just go round and round in circles and remain unresolved.