Weller magnastat tip problem

[BurningTantalum]

I have just persuaded a non-EE friend to purchase a bargain Weller magnastat station with 2 irons and spare tips. This works fine and he is pleased.
I was issued with a PU1D in 1974 and used various models through 2 jobs until I changed to Pace gear in the 90s, so have a store of spare parts.
I ferreted out a handful of used and new tips for TCP1 and the larger 60 and 100W irons to donate to him but found that non of them had any magnetism in the tip insert, thus they do not attract the switch slug and do not heat up.
I have never come across this issue and can find no reference to it anywhere.
What has happened? They have been stored in a plastic drawer with other spare iron tips and spares- nothing else magnetic. Some of the second hand ones could be up to 40 years old max but the new ones not more than 20 years.
BT

[Gyro]

Ah the wonderous Magnastat, I still use my TCP every day and it's still more effective than a lot of the modern electronic ceramic element ones.

The tips themselves aren't magnetic, they are ferrous alloys. The magnet is inside the therno-switch assembly down the center of the element. The slug on the back of the tip attracts the magnet until it reaches it curie point temperature, when it stops attracting the magnet.

If the magnet isn't being attracted (you should hear a click as you insert the tip) then either the thermo-switch has been pushed too far back in the barrel and stuck, or the plunger in switch assembly itself has stuck. If you hear a click when you insert a bit, then it's the switch contacts or some other wiring fault.

If something has stuck (and the iron hasn't been used for a while) then try tapping the iron with the tip removed end downwards onto a piece of wood. That might be enough to loosen thing up again.

As far as I'm aware, there's no age related deterioration of the slug on the tip, it's curie temperature is set by alloy composition only, so they should be fine, regardless of whether the iron works.

BTW: I fitted my TCP with a 5 core lead and use the termo switch to control a SSR in the base unit. That removes the contact loading from what is the most expensive component in the iron (elements, handles etc are pretty to very cheap).

[SingedFingers]

+1 for tapping the iron. My old 1980s TCP got stuck recently and that cured it for a bit. Then the element went pop a couple of weeks later. Think it's corrosion related on mine.

TBH I couldn't be bothered with sorting it as the PSU is held together with duct tape after being knocked off the old tiny bench I had numerous times and grabbed a new WTCP51 kit and will use that for another 30 years. They've changed the tips to an adapter slug that sets the temperature (700/800oF) and then an LT series tip in the end now which is a bit weird but the tips are cheaper! Might be a good upgrade for the older irons.

[Gyro]

They've changed the tips to an adapter slug that sets the temperature (700/800oF) and then an LT series tip in the end now which is a bit weird but the tips are cheaper! Might be a good upgrade for the older irons.

I've wondered about that, but I'm not sure about that flat ended thermal interface between the adapter and that little LT tip versus the much higher mass and coupling of the original TCP tip.

[SingedFingers]

I thought that initially and considered buying some new tips but TBH I really can't tell the difference in use. They are a bit of a dick to change half way through a job though; you can't do it with some folded kitchen towel while it's still hot as the old tips as you have four parts to argue with rather than three and one is considerably more fiddly. I switch back and forth between a 3.2 and 2.4 chisel (long) tip regularly so this is a bit of a problem. 2.4 for general work  3.2 for bastard great big capacitors.

Actually I've just persuaded myself to check tip compatibility and buy some new ones now

[Gyro]

That's good to know, thanks. I might give it a try myself then given that it's a cheaper option. 

[SingedFingers]

Just to add, it looks like there are is a larger variation in LT tips available as well.

[BurningTantalum]

Thanks Gyro and SingedFingers.
As soon as I started to read Gyro's post I remembered: the embarrassment crept in but then I realised that it was nearly a quarter century since I had played with one of these.
At my first job we all had PU1Ds and thus were able to cobble together units out of scrap bits from the stores bin to take home. In fact there was a 44 gallon drum as a scrap bin at the end of the stores counter, and we would ask Old Joe for the new part and as he turned away to the shelves we would toss a few screws into the bin to audibly simulate throwing the old Weller part or side cutters etc into the bin. Thus we acquired a BNIB part to take home. I know, I know, but my boss did it too... victimless crime...
We progressed onto PU2Ds which had the silly terminal posts for the iron lead- this just encouraged people to use the PSU as a 24V supply; not a good practice as I think that the 3A fuse was wound into the transformer (was on the PU1D anyway...)
I too became sick of peeling the yellow tape off the switch cover and running a contact file over the contacts so tried various ways of incorporating a Triac, or rectifying it for a Thyristor. The problem was that there was no room at all in the handle.
I had a block of pine on my bench to tap the tip on if things went cool.
I tried in vain to find some 5-core silicone covered cable.
Eventually in 1987 I became an industrial prostitute and worked around the world so carried a horrible 25W Antex without stand because of luggage limits.
I like the idea of removing the numbered slug- maybe a turned end on a tip to meet up with it and some thermal grease would be of benefit.
I quite fancy another TCP1.
I fitted 2 spring holders on my PU1D, and at one point had a hard wired 240V 60W TCP with big hoof in one holder and the other carrying a 48W TCP with fine cone tip connected to the Bulgin socket.
I tossed the lot a few years ago and now regret it deeply.

The story of the cold tips was second hand from my friend- it turned out that he had blown the 3A in line fuse- the unit (type no unknown, with the 'bent up front') had a strange (3-pins nearly inline with bayonet twist) socket fitted but the 2 irons had the standard (for me) 3-pin Bulgin so I gave him a Bulgin socket and left him to fit it.
His handles are more modern that my old ones- Instead of the twist-on 'wire nuts', or whatever they are called, there is a white plastic frame with rivets to which the contact and element wires are soldered- much neater.
Thanks all for the nostalgia !
BT

[SingedFingers]

Nostalgia indeed. My first iron was a TCP1 and PU1D which my father "borrowed indefinitely" from work and I "borrowed indefinitely" from him. I saw a new in box one on ebay a while back which I nearly grabbed for the sake of nostalgia:

http://www.ebay.co.uk/itm/Weller-Soldering-Iron-Station-x2-1x-W-TCP-2D-with-temperature-controlled-/302211477693?nma=true&si=%252Fy9F45A%252BMBz9Y4M62eSvanKGXbs%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

I also have an Antex firestick, an XS25. It's quite useful but no patch on the Weller irons. I might shove it on eBay later actually.

[Andy Hoffman]

If I may resurrect this topic after a year of being dormant . . . . .  regarding the Weller Magnastat soldering iron internal Magnastat switch assembly.  I've just carried out a full post mortem on my switch, having totally taken it apart into *all* of its component parts.  The switch's internal sliding magnetic slug (to which the bit is magnetically attracted) has a slim (mechanical) wire brazed to the end of the slug, the other end of the mechanical wire being inserted into a yoke that holds/actuates the switch contacts.  But I cannot see any spring that keeps the switch contacts open when the iron is not calling for heat/unpowered/at rest.  Does anybody know what provides the spring action that keeps the contacts open? Without that spring action holding the contacts open, the switch contacts would open/close depending on which way up the soldering iron is held.  Thanks.

[Ian.M]

I've never stripped a Magnastat switch down that far.   Usually it was just a matter of removing the rear cover to dress the contacts and I no longer have any Magnastat irons to examine hands-on.

I've read elsewhere that the restoring force is provided by a ferromagnetic slug (hollow, with a Curie point higher than the max bit temperature available) behind the magnet on the end of the actuator wire that moves the switch contacts.   Obviously its spacing and thickness must be arranged so it attracts the magnet less than the Curie point slug on the bit does below its Curie point temperature.

However the original Weller Magnastat US patent mentions a coil spring in the switch assembly: 20 turns of .007" dia stainless wire with an O.D. of 1/8" providing a restoring force of 20 grammes (page 9, 1st column, line 18), so it may vary from model to model.

[Andy Hoffman]

Ian.M, thank you for your reply.  I'll check and see if there is a hollow ferromagnetic ring/slug in my dismantled Weller switch. Your description of how such a 'restoring function' slug might work makes a lot of sense.  Likewise, the mention of a spring.  Your attached original Magnastat patent drawings are a work of art!  Again, many thanks for your reply, really appreciated.