Hornby R3748 Double Decoder Set-Up

[Chrissaf]

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I recently short-circuited an LED whilst re-fitting a Class 66 Body onto its alloy chassis. This mistake  caused damage to the installed Hornby Class 66 R8121 TTS Sound Decoder. Subsequent testing revealed the only fault was the Rear Lighting control (Yellow Wire Pin 2 on the 8 Pin Socket used by Hornby). The Front Lighting, Sounds and Motor Control all worked perfectly. At a cost of £40, the Good News was my TTS Decoder was only slightly faulty, therefore still very useable.

I decided to purchase Hornby’s New R3748 entry level Co-Co Class 66 Loco No. 66789 (£67.50) and install my slightly faulty TTS Decoder. After some further pondering, I further decided to make this a Class 66 Loco Project. I liked the idea of retro-fitting DCC LED Directional Lighting but really wanted both Front & Rear Lights working. In my spares box, I had 4 Hornby R8249 DCC Decoders which can control Directional Lighting.

So my idea was to install  my slightly faulty R8121 TTS Decoder into the Loco DCC Socket for Sound & Motor Control whilst installing one of my spare R8249 Decoders into an additional DCC Socket to control the Directional Lighting. I purchased the DCC LED Light-Units from a well known UK Auction site for £21 and already had a spare 8 Pin Socket as used by Hornby.

Installing the LED’s into the Loco was, fairly straightforward, being carried out as per the supplied Instructions. This does involve drilling the Loco Body / Chassis as well as carefully melting 1mm diameter Fibre Optic cable to form lenses for the 4 Tail-Lights and 2 Top-Lights. The 2 “Day-Time” Head-Lights have their lenses made from Lighthouse LED stalks. So all in all, not really a job for the Faint Hearted.

Next was to prepare the additional DCC 8 Pin Socket  with particular attention to the  Socket Pin Orientation. I carefully soldered 5 thin wires to the Socket as Follows;

Yellow    to Pin 2                Rear Light Control -ve

Black      to Pin 4               Left Rail Power Pick-Up

White     to Pin 6                Front Light Control -ve

Blue       to Pin 7                Light Common +ve

Red        to Pin 8               Right Rail Power Pick-Up

 

The Power Pick-Up Pins 4 and 8 need to be soldered to the same Pins on the Loco Socket (4 to 4 & 8 to 8).

It should go without saying that any soldering or Plugging / Unplugging Decoders must only be done whilst NO POWER is being delivered to the Loco.

The additional Socket can now be secured to the chassis adjacent to the Loco Socket using Double Sided Foam or Black-Tac. The remaining 3 thin wires (Yellow, White & Blue) were left about 50mm long, about 8mm bared at the ends and Tinned. Each wire was temporarily protected from short-circuit with insulation tape and will be connected to the colour coded DCC LED Lighting wires.

The next Stage is about programming both Decoders and is appropriate to mention that my DCC system uses Hornby’s e-Link with RailMaster Software. The beauty of DCC is that you can control multiple Locomotives on the same track because they each have a unique Digital ID address (which is user Definable). It seems standard practice that all Manufacturers program their DCC Decoders ID at the Factory to be a default 3. If two Locomotives are subsequently put on the same track with identical Digital ID’s the DCC system will return a Conflict Error which needs to be resolved before control can be resumed.

Because I am using two Decoders, a separate Loco Control panel for the Sounds - Motor Control and another for the Directional Lighting Control, would seem to be required. I want to set up my Co-Co Class 66 No. 66789 Locomotive on RailMaster so that I can have Directional Lights, Sounds and Motor Control using just one Loco Control Panel. To achieve this, both my R8121TTS and R8249 Decoders would need to have the same ID number. This is not difficult to achieve but can be a somewhat time consuming and confusing process. The process I used is as follows;

1. Insert the R8249 Decoder into additional DCC 8 Pin Socket.
2. Remove DC Blanking plug from Loco DCC 8 Pin Socket
3. Place Loco on Programming Track.
4. Add DCC Power and Select Hornby R3748 Co-Co Class 66 from RailMaster Database.
5. Run Decoder Self-Test (assume Factory ID 3).
6. When finished, Re-number the Chip ID, to its New Loco Digital ID number.
7. Remove from Programming Track - Insert the R8121TTS Decoder into the Loco Socket.
8. Unplug the R8249 Decoder - Place Loco on Programming Track.
9. Add DCC Power and re-Select the R3748 Loco ID 3.
10. Then Run the TTS Decoder Self-Test (assume Factory ID 3).
11. When finished Re-number the Chip ID as the previous Decoder ID.
12. Remove from Programming Track and re-insert the R8249 into the additional Socket.
13. Place on Programming Track and Set-up Hornby R3748 again using New ID Number.
14. Re-run the R8121TTS Decoder Self-Test again - then allocate sounds to the "F'' Keys.

NB.

1. I find that when running some TTS Decoder Self-Test’s I have to let Railmaster know it is a TTS Decoder by double clicking on C/V 7 (Decoder Firmware Version) and select the appropriate option from the Dropdown Menu. If the Test doesn’t ID the Decoder as TTS it will read every C/V address from 0-255 which takes ages.
2. It is important that the R8249 Decoder is only inserted into the additional 8 Pin Socket so that when Programmed, it doesn’t read/store Motor settings. This may well conflict, with the R8121TTS Decoder Motor Settings, causing running issues.

My Hornby R3748 Co-Co Class 66 “British Rail 1948 – 1997” No. 66789 Locomotive now has both Decoders installed with each having identical Digital ID’s.  Having solder connected the Directional LED Lighting wires to the 3 thin wires on the Additional DCC Socket, refitted the Body to Chassis, the Loco was placed on my Track, Powered-Up and Hey-Presto, everything worked perfectly. Yes the Sounds are Brilliant, Motor Control very Smooth and the Directional Front – Rear Lights work exactly as they should. I am Very Pleased with the finished result, which has Enhanced my entry level Hornby Locomotive, as well as being an  interesting addition to my small Collection.

I hope this Project has  been of some interest to others. I’m not sure if this is only a one off scenario, for a Double-Decoder, but at least I now know two Hornby Decoders can be run simultaneously in the same Locomotive using a single Control Panel.

Regards,

John K

[96RAF]

You could of course have saved yourself a lot of work (good write up BTW) and invoked Hornby's no quibble warranty for TTS decoders, which includes accidental damage - sales receipt required.

 

It is common practice to run two or more decoders on the same address such as when installed in multiple units.

[JK1707821688]

Hi RAF96,

Thank you for your kind comments and confess, I was not aware of Hornby’s no quibble TTS Decoder Warranty, for accidental damage. I will certainly keep this in mind for the future. That said, even if I had known about this arrangement, I would still have completed this project just for the fun, the learning experience and the final positive outcome. Also, a redundant R8249 Decoder seems such a waste of a DCC Device, which now serves a useful purpose. I just need to think of some intuitive projects, to utilise the 3 other spare R8249 Decoders. I will explore the Hornby Forum for ideas although any thoughts from members would be very welcome.

Regards,

B.John.K