Resistance Soldering Unit

DaveHarris
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Resistance Soldering Unit

Postby DaveHarris » Sun Oct 04, 2020 8:24 am

I, like many others i suspect, have looked at resistance soldering and wondered if the cost versus use equation was worth it. I have recently found an advert for a British company, Frost Equipment, who offer a resistance soldering unit at half the cost of the popular LRM model.
Has anyone any experience of this unit, good or bad?

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David B
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Re: Resistance Soldering Unit

Postby David B » Sun Oct 04, 2020 9:22 am

Is this the unit? https://www.frost.co.uk/carbon-resistance-soldering-system/

I see the two reviewers both mention railway modelling, one 7mm, the other does not say what scale. The unit has an output of 6v which is much higher than the LRM RSU (though how this relates to current I do not know) and only two settings, 'standard' or 'high' current. On the LRM unit, I have never used more than 3v and that was on a 7mm job.

With only two settings, it will not be as controllable as the LRM unit which has a voltage range from 1 to 4.5v more settings so I would not like to use the Frost unit on smaller, delicate jobs or white metal as I do regularly. I find that changing the voltage on the LRM unit by just 0.5v makes a difference. If I am putting brass on to white metal, 2v is more aggressive than 1.5v. I can't speak for the Bernard Weller unit or any others.

The price is certainly attractive, but I question it's suitability and flexibility for 4mm modelling. My thought is that this would be better suited to 7mm or larger modelling, but others may think or know differently. Having the experience with the LRM unit, I would not consider one of the Frost units for myself.

You ask of an RSU, 'is it worth it'? It is an investment and I suggest the answer depends on your age and how much use you might make of it in your modelling. An LRM unit would be a better investment for a younger person but once one retires with hopes to spend more time modelling, it can still be a worthwhile investment. The unit is durable and will last for many years. They also have a good second hand value though they do not come up very often. I have heard of LRM units changing hands for more than £120. If you don't want to pay out for a new LRM unit (currently £210 + p&p), look for a second hand one.

Bill Newstead
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Re: Resistance Soldering Unit

Postby Bill Newstead » Sun Oct 04, 2020 9:30 am

There is a review of sorts here: https://platform1mrc.com/p1mrc/index.ph ... ment.3346/ The thread ends with no evidence that the buyer actually used it.

I have an LRM unit. In my experience it is a quality bit of kit, aimed squarely at railway modellers and worth every penny.

Bill

DaveHarris
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Re: Resistance Soldering Unit

Postby DaveHarris » Sun Oct 04, 2020 2:53 pm

Thanks for the comments gentlemen.

Not being an electrician I wasn't sure about the differences in outputs, but was thinking that the cheaper unit wasn't as 'flexible' as the LRM unit, hence my question.

As you say , the LRM has been around for a long time with a good history.

Will just have to consider if I can justify the cost to the 'boss'! ;)

Philip Hall
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Re: Resistance Soldering Unit

Postby Philip Hall » Sun Oct 04, 2020 4:06 pm

Having looked at the review mentioned I wouldn’t touch it. The transformer box is very small, plastic, with quite a thin mains lead, and for the kind of current floating around makes me nervous. The foot switch (what a name for a small button!) being mounted on the transformer box means that you would have to look down at the floor each time to find it.

You get what you pay for. The LRM unit is built well robust and safe and works very well.

Philip

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David B
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Re: Resistance Soldering Unit

Postby David B » Sun Oct 04, 2020 6:03 pm

I hadn't realised that red button was the so-called foot switch. It's quite inadequate. No, this does seem very 'second' when put up against the LRM unit.

nigelcliffe
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Re: Resistance Soldering Unit

Postby nigelcliffe » Mon Oct 05, 2020 9:12 am

I agree with Philip and David, from what I can see on the maker's website and the "review" posted, don't bother. Output levels are not clear, foot switch is hopeless (I'm less worried about the mains lead - the currents at mains voltages shouldn't be high ).

I've had a LRM unit for many years; its rock solid, and I use a lot of the different outputs.

David Thorpe

Re: Resistance Soldering Unit

Postby David Thorpe » Mon Oct 05, 2020 10:08 am

It perhaps speaks for itself that the "review" Bill mentioned above says a lot about the unit prior to use, but nothing at all about it actually being used.

I've got one of Peter LeJeune's Swanage Models units; solidly built with a hefty metal case, CE certification,6 outputs, proper footswitch, and when I bought it it cost about the same as the LRM unit, which was not then available. It's worked perfectly and I expect it to continue to do so. i've no idea whether they're still available.

DT

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Martin Wynne
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Re: Frost Resistance Soldering Unit

Postby Martin Wynne » Sun Nov 07, 2021 10:42 pm

Just noticed this topic.

It's essentially just a transformer. So the nominal 6v output could be reduced to 3v by running the unit on 115v mains. Which could be done by including a step-down autotransformer in the mains connection. One like this for example:

https://uk.rs-online.com/web/p/autotransformers/0504202

That brings the cost closer to some other units of course, but might be better availability.

Martin.
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Jol Wilkinson
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Re: Resistance Soldering Unit

Postby Jol Wilkinson » Mon Nov 08, 2021 1:16 pm

Add the cost of a step down transformer (plus a case for it, leads, etc) to that of a RSU which is something of an unknown quantity and you are getting towards the cost of an RSU from one of the of the established suppliers such as London Road Models.

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Martin Wynne
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Re: Resistance Soldering Unit

Postby Martin Wynne » Mon Nov 08, 2021 2:20 pm

Jol Wilkinson wrote:Add the cost of a step down transformer (plus a case for it, leads, etc) to that of a RSU which is something of an unknown quantity and you are getting towards the cost of an RSU from one of the of the established suppliers such as London Road Models.

Hi Jol,

The autotransformer which I linked to is cased (or at least shielded) and fitted with cables, and from a reputable supplier.

I mentioned that the total cost would be approaching that of other suppliers, but there are reports on other forums of current supply difficulties for RSUs from the model trade.

One point in favour of the Frost unit is that by using it without the autotransformer you still have a unit suitable for its original intended purpose -- car restoration. I doubt the RSUs available from the model trade can be used for that.

I agree that the Frost unit is an unknown quantity, but it should be possible to find reviews on car restoration web sites.

cheers,

Martin.
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Jol Wilkinson
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Re: Resistance Soldering Unit

Postby Jol Wilkinson » Mon Nov 08, 2021 7:44 pm

Martin Wynne wrote:
Jol Wilkinson wrote:Add the cost of a step down transformer (plus a case for it, leads, etc) to that of a RSU which is something of an unknown quantity and you are getting towards the cost of an RSU from one of the of the established suppliers such as London Road Models.

Hi Jol,

The autotransformer which I linked to is cased (or at least shielded) and fitted with cables, and from a reputable supplier.

I mentioned that the total cost would be approaching that of other suppliers, but there are reports on other forums of current supply difficulties for RSUs from the model trade.

One point in favour of the Frost unit is that by using it without the autotransformer you still have a unit suitable for its original intended purpose -- car restoration. I doubt the RSUs available from the model trade can be used for that.

I agree that the Frost unit is an unknown quantity, but it should be possible to find reviews on car restoration web sites.

cheers,

Martin.


Hi Martin,

I hadn't noticed that the transformer shown in the link had cables fitted.

I know only of the supply situation relating to the LRM unit. These are usually produced in batches of 10 or occasionally 20. John Redrup supplies direct although they are occasionally available through Hobby Holidays as they attend the GOG shows.

They are expensive to produce and require a significant investment in the parts, notably the case components which have to be purchased in quantity from the manufacturer. The supply of transformers has also subject to minor component supply issues and the increased cost of steel for the laminations and copper for the windings (although that hasn't yet been reflected in the price).

Over the years there have been several articles on inexpensive DIY RSUs based on 12v battery chargers, etc. However these don't seem to have taken over the market. The Frost unit mentioned earlier in this thread operates at 6volts, the website gives no indication of power rating (VA or watts). It may therefore be suitable for some jobs. The two reviews rather indicate the user was modelling in 7mm or larger, whereas the LRM and Swanage Models units have a variety of settings to suit different requirements.

Jol

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Martin Wynne
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Re: Resistance Soldering Unit

Postby Martin Wynne » Mon Nov 08, 2021 8:27 pm

Hi Jol,

In reply to my suggestion of an autotransformer on another forum, this has been posted:

"You can purchase a 240/110 portable transformer for about £10 on eBay. Additionally, a US 2pin to UK 13A adapter is available for about a fiver."

I know nothing about that, but if true the cost calculation is much more favourable.

This one with a UK plug is claimed 200W, and £20 on Amazon:

https://www.amazon.co.uk/dp/B097R2J3KS

Given the very short pulse duty cycle, the power rating is a bit academic.

cheers,

Martin.
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