Resistance Soldering Seminar.

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Resistance Soldering Seminar.

Postby steamraiser » Sat Aug 24, 2019 3:56 pm

The Bristol BS4 group accepted an offer by David Brandreth to give us a days tutorial on Resistance Soldering.
The Seminar was organised by Robin gay and Paul Bannerman.

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Part of the BS4 group hard at work.


From left to right: Paul Townsend, Robin Gay, Paul bannerman and Ashley Phillips.

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From left to right: David Nicholson (Guest and S7 modeller) David Brandreth, Nigel Newling and Paul Townsend.


Left to right: Ashley Phillips and Pete Tarver (Bristol).
There are only two people missing from the pictures of persons attending the seminar; Richard Lane who had left after lunch to support Yeovil town and myself.

We all agreed that it was an excellent day. A light lunch plus tea, coffee and biscuits were included.
Every one who attended enjoyed themselves.

our thanks to David Brandreth for talking us through the advantages of resistance soldering.

Gordon A

PS I had straightened the first and third pictures before posting!

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Re: Resistance Soldering Seminar.

Postby Flymo748 » Sat Aug 24, 2019 5:23 pm

steamraiser wrote:The Bristol BS4 group accepted an offer by David Brandreth to give us a days tutorial on Resistance Soldering.

PS I had straightened the first and third pictures before posting!

If you click on them, they re-orientate themselves correctly...

Beware of Trains - occasional modelling in progress!

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Paul Townsend
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Re: Resistance Soldering Seminar.

Postby Paul Townsend » Sun Aug 25, 2019 5:33 am

It was a very useful and sociable session.

I have used an RSU for certain jobs for 20 + years, ever since Bernard Weller introduced me to the technique, and especially a lot last year building Broad Gauge baulk road so had considered I had little to learn but went along on principle to support a group activity.

In the event I came away with notes on 10 tips that were new to me and a gift from our generous David B.

Well worth the effort, so many thanks to David, Robin for organising it with support from OP ( Paul Bannerman) and his family for the venue and lunch.

For interest, I took along meters and test gear to assess the output capabilities of the 9 RSUs present.
Dave N and myself had original Exactoscale units, bought as naked transformer and DiY packaged in my case, DN's may have also been in a DiY or Bernard's box. Gordon had an ancient one of uncertain origin and Ash had a recent DiY job. The other 5 were identical London Road transformer boxed units.

Probes and return clip leads varied, the best for most jobs being the most recent LR design with proper screw collet. Gordon's superior pencil sharpener gave us a better working tip. I also displayed the luxury American Beauty tweezers, great for certain special tasks such as my baulk road.

All boxes delivered selectable voltages between about 1.9v and 3.1 v to a dummy load of 0.22 ohms on short wires so currents maximised at 8.6 to 16 Amps. The LR boxes offered lower settings of 1 and 1.5v nominal too. Gordons gave down to 1.25v on load. Measured performance " on task" varied much more due to variable contacts quality at probes and return clips and thickness/length of leads in use. I saw 1.0v to 2.4v at the load and currents between 6.5 and about 12Amps at real loads with probes or up to 16 Amps to the dummy load.

The London Road boxes provide lower settings than any of the older or DiY machines and that seems to me an advantage for the most delicate tasks.
Being a well-equipped Electrical bod, I have a Variac ( variable mains transformer) at home so can reduce the mains input voltage to my transformer and get lower power at the tip if required. In practice I have not used that yet but will try it for such as carriage tee handles.

All the devices seen were capable of delivering the range of outputs required for most 4mm tasks in the hands of experienced users with good supporting tools such as a SMALL steel plate to work on. Some of us had large 1/4" thick base plates as advocated by Bernard but these do act as an undesireable huge heat sink so force one to use higher output settings at the transformer and greater risk of vapourising the smallest components.

It seemed to me that the best base plates seen were of 1.6mm plate and only around 100 x 50 mm mounted on a small block of wood with a non-slip rubbery bottom.

Of my 10 tips gleaned here is my top tip from David Brandreth:
Drill your return pillar, typically a 6mm or 8mm machine screw, with a cross hole of 4mm. You then use a double ended 4mm banana plug lead as return which is superior to a giant croc clip on the screw thread as used by many of us.

I add a cautionary safety note mainly for anyone attempting a DiY job:
Ensure that your transformer meets modern safety specification, in particular that the secondary is on a separated compartment bobbin. Old transformers with the secondary wound outside the primary are now deprecated and especially in this application present a hazard of the hot secondary breaking down the thin insulation so connecting your hand held probe to 240v. You would only do that once :(
Get it PAT tested and certified.

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