Decoder Installation in Farish Diesels  by Gwyn Humphreys

FITTING DECODERS IN OLD ORIGINAL FARISH  CL.37/47. DIESEL LOCOS.   (Including Cl’s. 50. 52. 55. with similar chassis block.)

First part of procedure.

If the loco is new or has not had a lot of running, run it in for 30mins or so in both directions.

OR

If it’s an older loco, it should be already run in.

1. Remove the body, and place it aside until end of project.

2. Use fly leads with crocodile clips from controller and connect to chassis and the isolated pickup screw on top of the loco. Turn it upside down and use the controller to run it, and use a fibre pen or other method to clean the wheels – which is a lot easier when the bogies are running. Also, using a pipe cleaner or something similar, carefully clean the pickups on the bogies.  Having clean wheels and pickups is a vital part of a successful installation.
3. NEXT.

Remove both bogies, clean the pickup contact plates (square copper pieces) and place bogies on one side.

Remove everything off the top of the chassis.

Be aware there are three different types of (black plastic) top plates. Two are almost identical, but one of them has cab lighting pickups. The third is a fair bit shorter with no lighting pickups.

The one with the lighting pickups – cut the wires to the diodes leaving a short tail to the pickup for later connection to the decoder. You should now have a bare black plastic cover plate (unless you have the one with lighting pickups which you have retained in situ for later lighting connections).

At this point, decide which is the number 1 cab end of the loco (this reason will become obvious later). Having decided this, temporarily place you decoder approximately 5mm from the number 1 end (with the wires running back along the plate, and equi-distance from the sides. Mark the decoder’s position with a pencil or craft knife.

Next, drill four small holes in each corner inside this oblong piece. Then, using a sharp craft knife cut between each hole (taking a number of strokes), until you can remove the oblong piece leaving a nice clean hole which should be slightly larger than the decoder.

Fig.1. (above) should give a rough idea of what to do – disregard the wiring connections for now I’ll refer to them later.

Now put this plate aside, and turn to the chassis block !

                    COVER PLATE WITH RECESS FOR DECODER.

 (Note gap alongside brush retaing clip for threading orange decoder wire to bottom brush).

THE CHASSIS BLOCK.

Remove the pole pieces and magnet, making a note of which side the spot on the magnet lies in the chassis block (mark the chassis to indicate this, it is important).

Remove the bottom brush, spring and brush holder – remembering to save the bottom brush holder (for further exchanges with Gerry Spencer when ordering some more, it is very important that Gerry has the old ones back to ensure recirculation, as new ones are difficult to obtain in any quantity!) Contact Gerry at  gerry@jigerspe.demon.co.uk  or Tel:  01476  550301.

Now turn to the armature and worm shafts.

Again there are two types of connections from the armature to the worm shafts.

The older types have white plastic universal joints. The newer types are springs.

1. With the older type, just lift out the armature.

2. With the newer type, lift out the armature and worm shafts in one piece.
3. Next, drill out the bottom brush hole with the 2.9mm. bit supplied with the kit. I find that an appropriate size pin vice is adequate for this job. Whilst doing this be very aware of the two copper pickups at each end which are riveted or ‘clinched’ to the chassis block. Any damage to these and your project is ruined DO NOT REMOVE THEM !  

Having drilled out the hole this is a good time to remove any ‘swarf’ around the hole and give the block a wash in meths or any proprietary cleaner. When it’s done, fit the modified lower brush holder, ensuring it goes in as far as possible with un-forced tightness. If you have access to a ‘continuity tester’, now check between the brush holder and the chassis to ensure they’re isolated. Give the two pickups a clean with a fibre pencil or whatever you’re used to.

Having done all the above, reinstallation of everything begins.

If you wish, this is the time to give the armature commutator a clean before installation, also to put the tiniest drop of oil on the armature and worm shafts white plastic bearings.

REINSTALLATION OF CHASSIS & INSTALLING THE DECODER.

1.    Re-fit the armature and where appropriate the worm shafts, ensure that the armature runs FREELY by flicking it with your finger. If it doesn’t, make sure the alignment of the armature and worm shafts in the block are correct and check again to ensure it is free BEFORE proceeding further.

2.     Place a piece of Kapton tape, or sellotape (ordinary electrical tape is a bit too thick)  on the chassis block  directly underneath the hole in the black cover plate (above the worm) where the decoder will be placed – this is to provide isolation for the decoder from the chassis block – DO NOT FORGET TO DO THIS – but is NOT necessary if the type of decoder that you use has already been insulated with ‘heat shrink’.

3.    Re-fit the bare cover plate (which will only go one way to align the top brush holder). See Fig 1. above and you will be aware that two of each different size (8BA.& 10BA.) screws retain the cover plate on the chassis.  At this point, it makes life easier if you fit either 8 or 10BA (as appropriate) solder tags under the heads of the screws before attaching the cover plate to the chassis. A good source for these solder tags are “Items Mail Order Ltd”, 46 St. Martins Road, North Leverton, Retford, Notts  DN22  0AU.  Tel:  01427 884319.  I would recommend that the bigger screws are fitted first – you will see that they go diagonally from each other.

4.     Then, fit the thinner and longer screw (with solder tags), turn the chassis over and these screws protrude through the square black plastic piece which isolates them from the chassis. Before you fit the little nut, clean the small copper pick up and fit it on the protruding end of the screw between the two small plastic posts which set the correct alignment of the pickup. Fit the nut and DON’T OVERTIGHTEN IT. Gently prise the pickup up to an angle that will give it light contact with the plate on the bogie. Repeat for the other end, but do not fit the bogies at this point. Now check again that the armature rotates FREELY. If it does, place the magnet and pole pieces in their respective positions (again without force), and placing the magnet in it’s original position with the ‘spot’ aligning with the mark you made on the chassis block at the outset.

NOW IT IS SOLDERING TIME.

The smaller your soldering iron bit the better, bearing in mind the size of the components that you will solder.

I use resin cored flux.

Looking at Fig 1. above, you will see the red wire crossing over diagonally from the small screw to the other small screw (on soldertags), and the same with black wire on the larger screws.

Most decoders – if not all have their type number on one side. Now place the decoder temporarily in the recess provided (type number upwards).

1.     Feed the orange wire through a cover plate hole near the commutator, measuring it to approximately reach the bottom brush retaining clip, past the side of the commutator (through the elongated hole alongside the brush holder and retaining clip), but allow an extra 1” and trim the wire accordingly, strip a small amount of the cover off the end and twist and ‘tin’ it with solder.

2.     Take the modified and unmodified brush retaining clips, clean the top and lay a small ‘blob’ of solder on both.

3.     Now insert the top brush holder, remembering to use the original solder tag underneath it (unsolder the tag from the original connection as it is a different size to fit the brush holder).

4.    Insert the brush and spring (it’s a good idea at this point to replace the brushes and springs with new ones if they’re a bit worn). Fit the original brush clip (which now has a blob of solder) to retain the top brush and spring in place.

5.     Insert the bottom brush and spring, and secure with the modified retaining clip. As mentioned above, now check with a continuity tester that the chassis and the clip are isolated, if not, I suggest you centralise the clip from the chassis by checking the gap (which is tiny) either side of it with a scalpel blade or similar craft knife. Do NOT repeatedly remove the clip (if avoidable), as it can wear down and damage the clip’s insulating properties. Now quickly solder the tinned end of the orange wire to the blob of solder already on the top of the clip.

Turn the chassis block over and be aware of the four pick ups hanging underneath.

6.     On top of the chassis you can now trim the grey wire’s length to the top brush, allowing an extra 1”, then ‘tin’ a small amount on the end. BEFORE SOLDERING THE GREY WIRE TO THE TOP BRUSH, BE  VERY AWARE  OF THE OTHER BLACK AND RED WIRES THAT YOU HAVE ALLREADY SOLDERED CROSSWISE ON THE SOLDER TAGS – TOUCHING ONE OF THESE WITH A HOT SOLDERING IRON CAN RUIN A VERY NEAT PIECE OF WORK. Being aware of the above, you can solder the grey wire to the top brush retaining clip – again with a quick touch to the existing solder ‘blob’.

7.     Now you can trim the black and red wires to size and solder them to their respective tag connections as per Fig.1.

NEXT.

DOUBLE AND TRIPLE CHECK THE ABOVE INSTALLATION PROCESS FROM 1. to 7. AND IF YOU HAVE DOUBTS, CHECK ONCE MORE.

The main checks being, a). That the armature rotates as free as possible. B). That the bottom brush and clip is isolated. And  c). That ALL solder connections are correct.

If all the above are OK, refit the bogies, tie off the remaining three wires (white, yellow and blue) with a bit of tape.

Put your loco on your programming track, and set your setup address to 03. Ensure the track is also clean, and everything being equal, your loco should run. If it does not move, or ‘smoke’ appears, take it off immediately, and re-check the above installation notes again.

I will add lighting installation shortly

©Gwyn Humphreys. UK.  26^th.December 2003.