How to shrink heat shrink tubing?
in [Repair]
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From: Michael A. Terrell on 15 May 2010 16:44 larry moe 'n curly wrote: > > Michael A. Terrell wrote: > > > > larry moe 'n curly wrote: > > > > <http://www.harborfreight.com/1500-watt-dual-temperature-heat-gun-572-1112-96289.html> > > $19.99 regular price. On sale for $9.99 at times. > > > > I received their weekly e-mail right after I posted. It is on sale > > for $7.99 with the coupon below: > > > > http://www.harborfreightusa.com/html/wkend0517/images/2.jpg > > > > Here is the user manual: > > > > http://images.harborfreight.com/manuals/96000-96999/96289.pdf > > > > > The diode in series with the heating element is a 1N5408, rated > > > for 3 amps average. The heater draws 8A average on low. > > > > > > So my question is, how long will this 3A diode last? > > > That 3 A rating is for continuous duty at > > a high operating temperature, not intermittent. The peak current rating > > is 200A. The case would likely melt before the diode would fail. > > > > > Doesn't the continuous amp rating for a diode apply for any load > > > lasting more than something like one 60 Hz cycle (or half-cycle?). I > > > normally run a heat gun a lot longer than that, ;) maybe up to 2 > > > minutes at a time. > > > > Have you used it for that two minutes? That should answer your > > question, and show that it takes more than two minutes to damage it. :) > > > > It takes time to heat the junction in the diode. The heat is > > produced only when forward biased, and is from the forward voltage drop, > > times the current flow. The higher the current, the faster it heats. > > Since a heat gun usually gets very intermittent duty in low heat mode, > > it works. > > > > If it can handle a couple 200 amp half cycles while charging an > > electrolytic in a piece of electronic equipment, it can handle the extra > > current for the heating element even though it is above the 3A > > continuous rating. > > > > It looks like the motor is run from a tap on the heating element. > > There is no schematic in the manual. I only saw the one diode, across > > the switch in mine. Also, how often will you use one on low heat? I > > rarely do, usually only when I accidentally hit the wrong end of the > > rocker switch. > > > > BTW, if that diode fails, all it will do is make it run at full heat > > in either 'ON' position. > > I'll bet customers will either not notice that the gun always puts out > full power (diode shorts), or they won't care that it doesn't work at > low heat (diode opens). I checked a few different items, including > some cheapo PC power supplies, and couldn't find any where the diodes > were underrated so much The usual failure mode would be shorted, unless the internal connection fractured and separated. > I bought this heat gun to desolder surface mount stuff, and it seems > that its low setting puts out temperatures closer to what hot air > soldering equipment does. I prefer full heat for that job. I just keep it a little further away from the board. I see less damage to boards that way. I used to have a 6" solder pot that I would float a scrap board on, then use a pair of pliers on the corner to smack it against something to eject all the molten solder. I recycled thousands of 256 kb memory ICs back in the '80s at $2.75 each. There was a huge shortage of new ICs, so they sold as fast as I could pull them and re-tin the leads. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: David on 23 May 2010 09:56 In article <8h5ku595n5519poblj8a724md77gbhtnbl(a)4ax.com>, mm <NOPSAMmm2005(a)bigfoot.com> wrote: > On Mon, 10 May 2010 16:24:04 +0000 (UTC), "Geoffrey S. Mendelson" > <gsm(a)cable.mendelson.com> wrote: > > >I've recently started doing electronic repairs (mostly wiring) and need to > >shrink heat shrink tubing. A long time ago I bought a heat gun used for > >removing paint and used that. It was 120 volt, so I left it when I moved > >here. > > > A cheap and easy way is to buy a hair dryer from one of the thrift shops - probably cost you a $1 or so, and does the job. David
From: David on 23 May 2010 09:59 In article <hsepor0qk1(a)enews6.newsguy.com>, mzenier(a)eskimo.com (Mark Zenier) wrote: > In article <slrnhugcn1.e0e.gsm(a)cable.mendelson.com>, > Geoffrey S. Mendelson <gsm(a)mendelson.com> wrote: > >I've recently started doing electronic repairs (mostly wiring) and need to > >shrink heat shrink tubing. A long time ago I bought a heat gun used for > >removing paint and used that. It was 120 volt, so I left it when I moved > >here. > > > >I've never had much luck (or is it patience?) shrinking it by holding it over > >a soldering iron tip. Using a flame, like a cigarette or stove lighter > >ends up with burnt plastic. :-) > > > >Is there such a thing as a small heat shrink tube shrinker that does not > >toast the things around it? The largest thing I need to shrink over is > >about 1/2 an inch most of them are small (20awg or less) wires. > > For cable assemblies, I've found that nothing beats a Sunbeam toaster. > Turns itself off, too. You don't have to put it down into the slot, > just hold it over the top. > > The trick with lighters is to keep the shrink about 1 1/2 to 2 inches > above the top of the flame. > > > Mark Zenier mzenier(a)eskimo.com > Googleproofaddress(account:mzenier provider:eskimo domain:com) I haven't tried it, but I reckon you could get an old pair of pliers - heat em up on the stove then gently grip the heat shrink with the hot jaws - might be worth a try David
From: Dave Platt on 23 May 2010 12:36
> Is there such a thing as a small heat shrink tube shrinker that does not > toast the things around it? The largest thing I need to shrink over is > about 1/2 an inch most of them are small (20awg or less) wires. You can buy small butane-powered torches, with a variety of tips. The one I bought has a flame tip, a catalytic-heater soldering tip, and a catalytic-heater hot-air jet. The latter works very well for doing small heat-shrinking jobs - with the torch turned down to minimum gas flow it produces a rather delicate and controllable jet of hot air which can heat the tubing without roasting things nearby. -- Dave Platt <dplatt(a)radagast.org> AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |