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· Premium Member
531 Posts
Discussion Starter · #1 ·
I accidentally broke two of the fine wires off a old Bachmann 2 function decoder that I was planning to use to operate the lights in the Bachmann Class 108 Dmu Trailer car.
The two broken wires are Red (right rail pickup) and Blue (function common positive).

Is it still possible to use the decoder to operate the lights only or would it be better to chuck it in the bin and start again with another decoder.


· Registered
525 Posts
No it isn't possible as the rail pick up is needed to receive commands and the blue is used for all the lights return voltage. It is possible to solder the wires back using a low power iron and or a copper wire clamped to the bit.

It is not uncommon for decoder wires to detach themselves.

· Premium Member
531 Posts
Discussion Starter · #4 ·
Thanks for the replies, dwhite4dcc & frame69

Looks like I'll have to manfacturer a soldering tip using a strip of copper wire attached to the tip of the soldering iron.

It will teach me to be more careful in future.



· Just another modeller
9,967 Posts
*** Hi

I'd really love to be able to kill this urban myth re the need for low power Irons. It simply is not true - Not for whitemetal or for small brass parts or for electronics or soldering to rail. In fact a low power Iron greatly increases yoour chance of failure! In particular for this thread, no electronic production line which hand solders fine parts ever, ever uses low power Irons!

The temperature will be the same whatever the power of the Iron - for electronics soldering between 350 and 38 is usually right.
The thing that makes the joint happen is the quick transfer of the correct amount of heat energy to the joint.

Iron wattage is largely irrelevant but it must be big enough - smaller or low power Irons often fail you or cause problems as they cannot deliver heat fast enough for a quick joint, making you linger and therefore adding far too much heat to the surrounding parts!!

What is needed is simply a physically small tip on a soldering Iron - it doesn't really matter what the power is as long as it is enough for the job - but in most cases a higher power Iron will give a quicker and therefore safer joint as the heat will be transferred immediately!

In my own case I have four Irons I use: I do the finest imaginable soldering AND some heavy stuff with the same Irons.

(1) A low voltage 25 watt Antex for "round the layout" use when a soldering station is too clumsy - this is as low as I would ever go and to be honest is OK for dropper soldering but only just good enough for soldering rail to rail.
(2) A 50 watt Antex TC660 temp control ssoldering station at home
(3) & (4) and at the office, A 55 watt Hakko soldering station and a 75 watt hakko soldering station - None have a "big" Iron physically but they can deliver whatever is wanted for anything and are superbly designed to deliver and maintain heat WHEN NEEDED - for example, the 75 watt Iron is as happy on an O gauge brass chassis as it is with a n0603 surface mount LED (Yet the Iron weights only 45 grammes - its super stable heat wise as the thermostat is actually in the tip itself so it reacts fast when more is wanted!!).

All are equally good at fine decoder work if the right tip, flux and solder are used. (reliable rework such a resoldering wires really does need a good flux)

The things that are important are:

If doing electronics is should ideally be ESD safe - many parts are static sensitive, particularly decoder chips! This rules out all cheapie Irons I am afraid.

An Iron with good power but small enough for comfortable use (it should feel more like a Mont Blank Pen than a clumsy Crayon)

A pure silicone lead so it doesn't drag on the hand

A tip that surrounds the element, not a "screw in tip" - screw in tips are really poor at heat transfer from elelment to tip

You also need / need to:

* to pre-tin the wire to be soldered to the decoder. (Strip, tin then snip off to a short length)
* remove all original solder from the joint (solder mop)
* to use a high quality solder - preferably not lead free as its much harder to use for the casual solderer than leaded solder. 179 degree leaded solder with silver added like my Sapphire 179 is the best there is.
* a good non-acid "no clean" flux. Yes I know solder is often flux cored but you have no space to take the solder to the joint with a tiny decoder, so adding flux where its needed then just taking a wee bit of solder on the Iron tip is sensible and prevent you needing three hands.
* An appropriate tip for the job - fine pint or very fine (1mm max) chisel for electronics, 2.5~3.5mm tip for heneral modelling work.



QUOTE (dwhite4dcc @ 8 Feb 2009, 04:58) <{POST_SNAPBACK}>It is possible to solder the wires back using a low power iron and or a copper wire clamped to the bit.

· Chief cook &amp; bottle washer
3,017 Posts
Thanks for putting that up Richard. I've always been of the same opinion, that you need an iron with enough power, not to go cool when you're trying to solder. I use a Goot 60 watt soldering station and only need to change tips for different jobs.
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