Re: International standards (2023 Update)

Thanks, John. What seemed a relatively small reduction in bulk was plainly rather more significant than I first thought. I'd guessed at least 2A, but will have to be content with much less. Not that I often need such heavy currents (and I have other supplies I could use in most cases). But it was comfortable to be able to largely ignore the setting.

Anyway, I needed to recalibrate the current limiting and current meter sections, so this removes any excuse for postponing it.

Thanks to all for the advice on this.

--
Terry Pinnell
Hobbyist, West Sussex, UK

My Weller and Metcal irons have a 'wet sponge' to clean the tip. I keep the sponges clean and very wet. Most people use the iron, wipe it on the sponge and put it back in the holder. I was told many years ago this is backwards. I wipe, tin, solder, add a bit more solder to the tip and put it back in the stand. The idea 1s that the solder will oxidize while its protecting the tip. Having built a few large projects, I have logged about 15000 connections with a single Weller tip. My $0.02 GG

As mentioned in Message-ID: it's the series power transistor, a 2N3716 mounted on the rear of the case.

--
Terry Pinnell
Hobbyist, West Sussex, UK

Hi.

My soldering iron (Antex CS 18W) tips seem to get rusted and pitted after a while. Any (sensible) suggestions on how to stop this from happening?

Thanks.

Travers

I read in sci.electronics.design that Terry Pinnell wrote (in ) about 'Estimating transfomer current rating?', on Thu, 12 Aug 2004:

I'd fit a bigger heat sink to it, then.

--
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

On Thu, 12 Aug 2004 04:17:19 GMT, Rich Grise wroth:

Soldering results from metals dissolving or alloying at the interface. If the base material of the spreader is something like aluminum which won't dissolve in tin/lead solder, then there could very well be a problem with a thin plating thickness. The original poster didn't state what the spreader material is and whether there are any other layers of intermediate materials involved.

Jim

two more from an old Oscar Brand record:

The steward's name was Andy A comely lad and randy. He used to cool his favorite tool In a glass of the skipper's brandy.

The first mate's name was Davy. Was cashiered from the Navy. Born of a w**re that was cast ashore A son of a beach was he. ( I know it doesn't rhyme but I still like it)

Friggin, in the riggin ...

-

- "Just machines that make big decisions programmed by fellas with compassion and vision." -D. Fagen (remove yomama)

I'm using a BUZ10 n-channel mosfet to switch a 1 ohm electromagnet coil on and off. It's been working OK for a while, and is now stuck open with a resistance of 11 ohm between drain and source, and around 50 ohm between gate and drain or source. Any ideas on what might have caused this? It's unlikely to be electrostatic damage, because there is a 10k resistor permanently soldered between gate and source, which was there before is started malfunctioning.

It has a heatsink on it - an aluminium screw-on one about 4cm square with

4 fins on it. Can't find the C/W rating for this.

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Glenn and John are right (as per usual). What I have found is that I have a lamp dimmer in series with my Iron, so I can turn it down when not in use. I use the type with preset pushbuttons, mounted in a plastic case. If I keep the iron "Idling" at the lowest setting, then turn it up full blast, it only takes a minute to get it up to temp. I average about a year (about 20 projects) per tip.I PERSONALLY have never had any luck with plated tips, and I really don't like them, but this is a personal taste thing. Also I find that at the end of the day, I lightly clean my tip with some FINE sandpaper, then flood it with solder, then wipe off the excess, then add a little bit of extra solder, without wiping (all of this done immediately after powering off the iron, while its cooling down). Every couple of days I do the same thing, but I also dunk the tip into solder paste after a light sanding, before flooding the tip with solder.

Kim

little

put a fly back diode across the solenoid coil. the cathode side on the + and anode on the - side of the coil.

andy wrote:

--- Sounds like you've punctured the gate oxide. You're only allowed 20V between the gate and the source or between the gate and the drain, and who knows how much inductance you have in the wiring, so when you switch the the thing off, you could easily be stressing the gate oxide to failure. The cure for this is to connect one 15V Zener from the gate to the drain, with the cathode connected to the drain, and another 15V Zener from the gate to the source, with the cathode connected to the gate. Use 1 watt Zeners and connect them as close as you can to the FET. Also, it wouldn't hurt to put a nice big electrolytic across the supply with the + terminal connected to the cathode of the 1N4001 and the - terminal connected to the FET source. But, not knowing how you've got this thing wired up, that might be easier said than done. Why don't you take a picture of what you've got and post it to your website so we can see what we're dealing with?

---

--- Probably won't matter much once the thing goes to work, since a total of two seconds ON out of every 86400 won't heat it up much. Also, fully enhanced, the worst case channel resistance is 70 milliohms, so even with 12A flowing through it, that's only 10 watts, and that's only for one second.

---

--- That's not a _bad_ idea, but the problem with it is that with the the

2N3906's emitter at 12V and its base incapable of being driven higher than 6V, it'll always be ON, so you'll need an NPN to drive it. That means more parts, a higher quiescent current load for the PV array, and since the regulator will have its own quiescent current requirements, an even heavier load on the PV. Life's a bitch, ain't it?^)

-- John Fields

While you are looking for the cause of the problem, send the failed devices to Altera for a failure analysis. They might be able to point you to a specific pin.

Good luck.

This sounds like there is a destructive EMF developing between the signal lines and ground at power-on. Mismatched transmission line effects? Can you add a resistor in the lines and a TVS? Also, if it works and does not fail with the shield connected, why not leave it connected?

It could cause large currents to flow if the source impedance of the impalance is low enough. However, the source impedance of the imbalance could be low enough to destroy a semiconductor without causing "large" currents to flow. What is the current due to ground imbalance?

Is there any reason why they have to be schottky diodes? The only ones I can find in Maplins are meant for power rectification. (1 amp plus max current). I'm thinking of using germanium signal diodes instead.

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forgot to say - the voltage is 12V DC from a lead acid battery. Drops to about 10-11V when the current is on. I've rebuilt it with a new BUZ10, and it's working again, but it would be good to have some idea why it faled.

also, I'm wondering if because of this voltage drop, I would be better running all the electronics in the circuit from a 6V linear regulator with a decent sized capacitor on the output, and just having the 2N3906 output driver transistor, the mosfet and the coil running from 12V. This would also mean I could use 74HC cmos instead of 4000 series.

The existing circuit is like this:

Is there any reason why this shouldn't work?

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--
Oops... 50V from the drain to the gate, and +/- 20V from the gate to
the source

Another solution is to use a steel plated tip. If your tip is bare copper, then what happens is the copper dissolves in the molten solder. This is why it pits. There are places to purchase plated tips, or you can invest in a little home electroplating and do it yourself.

Cheers!

Sir Charles W. Shults III, K. B. B. Xenotech Research

321-206-1840

thin

For heat spreader A,

1st layer will be Sn/Pb Plating, with 6-8u thickness. 2nd layer is Ni layer with 9-10u thickness 3rd layer Cu layer with 10u thickness 4th and the last layer will be the substrate, which contains Zn and little Al.

For heat spreader B,

1st layer will be Sn/Pb Plating, with 0.5u thickness. 2nd layer is Ni layer with 2-2.5u thickness 3rd layer Cu layer with 20u thickness 4th and the last layer will be the substrate, which contains Zn and little Al.

Surface element of the Heat spreader A is Sn/Pb mainly; while for Heat spreader B, the main elements are Ni and Cu, with little content of Sn.

Not zero resistance; impossible. The total I^2R losses were small compared to core magnetization losses.