Point Decoders

[jock42402]

Recently bought a load of accessory decoders from Ebay, first mistake! both R8217 + R8247 some have been fine but have had difficulty programming some of either unit. Is there a way of testing to see if the units are OK or do I throw them away and invest in new kit? It is frustrating to wire the unit up only to find nothing. Have used all the latest tech info from Hornby.

Regards Robin

[P-Henny]

R8217 is a Hornby Trakmat. R8216 is the earlier version of the R8247. Note that there are significant differences between the R8216 and the R8247, plus there are two versions of the R8247 (second hand versions of the R8247 are more likely to be the earlier MK1 version).

The key differences being:

You cannot read back R8216 CV values.

You cannot adjust R8216 pulse widths.

The R8216 needs to be pre-charged directly prior to programming, else programming will fail.

Personally, I would not trust ebay sellers that are selling these Accessory Decoders second-hand as they are easily damaged if exposed to transient short circuits on the track. I have had to replace a couple because of this. I would not be suprised to find damaged ones finding their way onto ebay as the damage is not obvious.

The damage can mostly be mild in that the decoder keeps loosing its configuration or corrupted and reports a negative value DCC port address or it just self resets to factory default or in severe cases becomes completely non-functional and can not be factory reset. The risk of damaging a good working R8247 can be reduced by fitting a "Snubber" filter across the DCC feed. Google 'DCC Snubber' for more information.

There is no easy way to do any electrical tests, as the output ports only have a pulse of power when operated, thus there are no constant standing voltages that can be measured to indicate their functional state when configured for the default pulse output. In other words, they either work or they don't work and to complicate matters they might not work due to incorrect programming or operation methods. So they might be perfectly OK and just subject to operator error.

For anybody to give a more informative reply, they need to know what controller you are using (Select, Elite or Railmaster) and in the case of the Select & Elite what is the firmware revision. The firmware revision appears briefly on screen as part of the power up self test.

If you are using Railmaster, there is an excellent FAQ in the "Railmaster FAQ Index" sticky that describes every step by step process for configuring and using both Accessory Decoder types. Worth reading even if you are not using Railmaster as some of the information given can be applied to the Select & Elite controllers (note if using a Select, the DCC Addresses MUST be in the 61 to 99 range).

[96RAF]

To add to the confusion some early acc decoders were incorrectly labelled. There is a date code on the lower case which is the error point 50/07.

This old post has all the details...

https://uk.hornby.com/community/forum/r8247-vs-r8216---is-there-a-problem-in-using-both-controllers-on-same-system

Note that on page 2 of that linked post there is another linked post that you should read also.

Ref damaged acc decoders, the only reliable test is resetting them, same as a loco decoder write value 8 to CV8 then following this procedure. Damage can be caused by having been operated by a Select at firmware v1.1 which knocks out port 1. Try a reset of the acc decoder and see if it works with a motor on port 2, 3 or 4. Do not press port 1 yet. If it works then select port 1 and likely it will fall over and nothing works until you reset it again.

Background info about this bug can be read here...

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