Have been using METACL SP200 solder stations for the past few years. Curious as to the mechanism of the tip's failing. Have had a batch of them that don't last more than a few weeks. All of the broken units heat up to approx 250C, hot enough to burn your fingers but no goos for soldering. Checking the heater coil resistance shows no DC resistance between faulty ones and new working ones.
Fault follows faulty tips when swapped to other base units and wands.
Any thoughts?
Louiiv
I'd send them back to Metcal. I've had a couple of MX-500 cartridges fail in the same way, but that was after a year or so. I don't know what the mechanism is, though.
Leon
assuming "no DC resistance" means "no difference in DC resistance"
"feels" like the temperature sensor part is faulty.
Probably right.
The Metcal works by feeding RF energy to a tip that consists of a copper core plated with a layer of ferromagnetic material that has a specific curie point. The plating heats up, loses its magentic properties, and the current flows in the copper with low loss and little heating until some heat is removed from the tip.
It sounds like you have a batch of tips on which the plating is delaminating from the copper. The plating heats up, but the heat isn't properly coupled to the rest of the tip.
BTW, measuring the DC resistance is just telling you the resistance of the RF coupling coil. It has nothing to do with the actual heating mechanism, except of course, that if it's open, the system won't work at all.
-- Dave Tweed
I second that suggestion. They do replace faulty tips provided they don't have any pliers marks on them and the plating is not cracked from bending etc.
Chris
The tip-caddy/holder is often the culprit. The center pin socket gets carbonized or such. I have seen it happen more than once.
Thanks for the replies.
Having taken one apart to see how it functions has not left me with any new thoughts. Just a slug of metal with a wire wrapped round it.
Info from the net suggests the base unit detects when one part of the tip passes it's Curie point. OK but still unsure how this can wear out or fail. De-lamination as suggested may be a cause and I shall have a closer look.
The tips I am using now are higher temperature parts for Lead free soldering so I guess there needs to be a different material used with a higher Curie point.
It is interesting (and beyond my) how the magnetized iron holder indicates to the base unit to reduce the tip temperature. If this function is not working the tip will be at max temp all the time and could be the cause of some of my tip failures.
I haven't looked into the lower frequency tips, only the 13.56MHz ones like PS2E and MX500. You can find out how they work by looking up their patents. I think that the original patents probably ran out a couple of years ago so anyone could build them now, which might partly explain why they shifted production to China, cost-reduced the design and dropped the price significantly.
In the original scheme for the PS2E type 13.56MHz tips, the tip does not need to send any information back to the RF source. I think they might have added some fancy stuff later on to detect when the iron is not being used, but that is not essential to the temperature control. I think that they run a constant RF current through the insulated silver plated copper coil which induces currents in the metal slug, and depending on whether the metal is below or above the curie point, the current either flows in the copper core (causing little heating) or in the resistive plating (some sort of nickel alloy IIRC) which would cause much more heating. It is a while since I read the patent so I can't remember.
I think that in some cases, the failures are caused by the fibreglass sleeving over the heating coil getting cracked causing a short circuit. In particular I think this might be what happens when people change tips using pliers. I don't really know.
Chris
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