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miffy 18-02-2018 11:19 AM

Soldering 25 pin Sub d connectors
I am about to start soldering 13 point motors and will be using 2 x 25 pin sub d plugs/sockets. There seems to be two schools of thought. Firstly, fill the cups with a small amount of solder, tin the wire then join without any more solder or put wire in cup then add solder to both at the same time. Is it just personal preference or is one way better than the other?


Silvernovice 18-02-2018 11:26 AM

When I did mine I used the second method, tinning the wire first. I tried the first but could not get the wires to sit properly

JonMiles 18-02-2018 11:26 AM

Personally, I have tried both and found for the smaller connectors and wires, such as the 25pin D-sub it was easier to pre-solder the cups, tin the wire. Then with a small amount of solder on the iron reheat the cup and insert the wire.

Maybe not the correct way to do it, but the way I find the easiest.

Steve M 18-02-2018 11:55 AM

Best practice is to tin the pin and the wire first. Then you only need minimal heat to bring them together thereby avoiding the risk of damaging the plastic holding the pins.

Another tip is to keep the d-subs plugged together as this provides a slightly bigger heatsink when soldering.

Footplate1947 18-02-2018 11:57 AM

Pre solder cups and tin the wires works for me. Unless they are in a difficult to get at position

Suzie 18-02-2018 12:11 PM

I am from the other school and never tin the buckets beforehand. Buy good quality gold plated 'D' connectors (look at the current rating in the spec to see which ones are better) and pre-tinning will not be required.

For 7/02 wires I twist and tin the wire first, then put it in the solder bucket and apply the iron and solder together to flow the joint nicely and fill the bucket.

With 16/02 the wire is a bit of a squeeze in the bucket so no real chance of tinning beforehand, so just put the stripped wire (don't twist or it won't fit) in the bucket, apply heat (for how long will depend on your iron, so practice to find out) then apply the solder. It is virtually impossible to put 16/02 into a tinned bucket!

To make the job look really neat put 15mm long heatshrink sleeves over the wires first then slide them down over the buckets and shrink them when the job is done.

You say you are using the connectors for point motors, in which case if they are solenoids you will need to use 16/02 wire to avoid too much voltage drop.

Suzie x

Walkingthedog 18-02-2018 01:26 PM

I agree with Suzie. Tin the wire not the cup. Insert wire, quick touch with iron, job done.

Rog (RJ) 18-02-2018 03:57 PM

I don't tin the wire or the cup. Just put the wire in the cup, apply the iron and the solder. No messing.
Did hundreds, if not thousands like this at work.

Walkingthedog 18-02-2018 03:59 PM

The choice is immense.

Flashbang 18-02-2018 04:09 PM

Well, I always pre tin the cups and the wire ends! :eek: IMO it saves a lot of aggro when soldering. Method I've used on possibly well over 200 plus D connectors is get a soldering iron with a good small tip and the iron of around 25 watt or higher wattage. Allow it it fully heat up - at least a full 5 minutes.
While its heating, I use a small clamp on vice with about 2 inch long jaws this G clamps onto the edge of my work bench. Use a good desk light and ideally one with a magnifying lens if possible to illuminate the work area. Using the lamp and magnifying glass I see which is marked as Pin 1 and place the D connectors metal body into the vice so as Pin 1 is on the left. I guess it really doesn't mater that much, its just the way I've found easy to do it.
Using 0.7mm dia rosen cored 60/40 solder pre tin (coat) the irons tip with a little solder then working along the rear row of buckets place iron tip onto each bucket and feed cored solder in then do the same along the other row of buckets.
Strip wire ends by about 3-4mm and twist up tightly the strands of each wire. Wipe irons tip on a damp sponge and recoat with fresh solder then pre tin each stripped wire end. Once cooled trim tinned ends to about 1.5mm long from insulation. This works for both 7/0.2mm and 16/0.2mm wire.
Wipe tip again on the damp sponge and lightly tin the irons tip. I'm right handed so I hold the iron in my right hand and the wire in the left about 1 inch or so from the tinned end. Hold irons tip onto the No1 bucket and within a second the solder inside will melt and the pre tinned wire can be pushed in. Once fully in remove iron and hold wire still for about 4 to 5 seconds to allow joint to cool and solder to solidify. 100% joint made. Move onto No 2 pin and repeat and so on until all wires are soldered into their buckets.
I like to ensure no possible contact can occur inside the D connector when its assembled so I then cut small dia Heat shink tubing to about 5mm long each and thread down the wire and over wire end and bucket. Use suitable heat source to shrink down all tubes. For cabled wires slip tubing on before tinning the wire ends then slide down after soldering all wires in place.
I mark the free ends of the wires with doubled over strips of 1 inch wide masking tape and write the pin number on each masking tape label e.g. 1 to 25 etc Assemble the D Connectors case/cover and job done.
9 way takes no more than 20 minutes and a 25 way max. 40 minutes to fully complete.This includes cutting wires to length, stripping them all and pre tinning then soldering in place and shrinking tubing over the buckets/wire, labelling free ends and assembling the cover.
I have never use gold D connectors and I cant see any point in doing so. They are not passing HiFi signals, so conventional ebay or other suppliers D connectors are IMO fine and all those I've used are rated at minimum of 5 Amp per pin, but I always double up the last two pins where a common return system is used. Only the other ends of the wires or cables are connected (doubled up) not the actual pins in the plug or socket. I usually terminal the layout ends into a row of terminal blocks, but that's a matter of choice.

Of course if you don't want to do soldering obtain suitable numbered way Break Out D connectors and cases. Like these... Example link I don't recall seeing 25 way cased ones though only the open version, but that doesnt mean they are not available!

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