How to shrink heat shrink tubing?
in [Repair]
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From: larry moe 'n curly on 14 May 2010 13:11 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 power switched popped out 3/16" when I pressed it (2 samples) > > Then why did you buy one? Mine is fine, and I just picked one off > the shelf, yesterday. I already have an old B&D, and a five year old HF > heat gun. The case on the B&D melted when I had to preheat some 1.5" > copper pipe while assembling the cooling system on an old TTU-25B UHF TV > transmitter. I also needed an acetylene torch & a 175W Weller iron to > remove some damaged copper pipe from some custom 30 year old brass > fittings RCA used in that transmitter. The HF has been used to remove > floor tiles, on heat shrink, and to expand metal castings to remove > bearings. > > > 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? > > Where is the 1N5408 diode? It isn't listed in the parts list or > shown in the drawings: > > http://images.harborfreight.com/manuals/96000-96999/96289.pdf > > How long to you use a heat gun per application? Can you read a > datasheet, or only skim one? 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. > > <http://www.datasheetcatalog.org/datasheet/GeneralSemiconductor/mXyztrxt.pdf> > > I've seen four 1N4004 diodes in a bridge, in series with the heater in > a hair dryer to power the dc motor on the fan. Are you claiming that a > tool like that can only provide less than 120 watts of heat? I bought the HF heat gun yesterday, and it has a manufacturing date of Jan, 2010. Here's a photo of the inside, showing the 1N5408 diode across the two poles of the switch: http://farm4.static.flickr.com/3315/4606961048_003af89634_o.jpg The switch popped out because the lower locking tab was squashed and couldn't lock. I think there's a bridge of small diodes at the end of the fan motor. 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.
From: Michael A. Terrell on 14 May 2010 16:40 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 power switched popped out 3/16" when I pressed it (2 samples) > > > > Then why did you buy one? Mine is fine, and I just picked one off > > the shelf, yesterday. I already have an old B&D, and a five year old HF > > heat gun. The case on the B&D melted when I had to preheat some 1.5" > > copper pipe while assembling the cooling system on an old TTU-25B UHF TV > > transmitter. I also needed an acetylene torch & a 175W Weller iron to > > remove some damaged copper pipe from some custom 30 year old brass > > fittings RCA used in that transmitter. The HF has been used to remove > > floor tiles, on heat shrink, and to expand metal castings to remove > > bearings. > > > > > 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? > > > > Where is the 1N5408 diode? It isn't listed in the parts list or > > shown in the drawings: > > > > http://images.harborfreight.com/manuals/96000-96999/96289.pdf > > > > How long to you use a heat gun per application? Can you read a > > datasheet, or only skim one? 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. > > > > <http://www.datasheetcatalog.org/datasheet/GeneralSemiconductor/mXyztrxt.pdf> > > > > I've seen four 1N4004 diodes in a bridge, in series with the heater in > > a hair dryer to power the dc motor on the fan. Are you claiming that a > > tool like that can only provide less than 120 watts of heat? > > I bought the HF heat gun yesterday, and it has a manufacturing date of > Jan, 2010. Here's a photo of the inside, showing the 1N5408 diode > across the two poles of the switch: > > http://farm4.static.flickr.com/3315/4606961048_003af89634_o.jpg > > The switch popped out because the lower locking tab was squashed and > couldn't lock. I've seen that in a lot of imported equipment, not just in tools. :( > I think there's a bridge of small diodes at the end of the fan motor. There were none external to the motor in mine. Just two 1/8" fastons that plugged onto the end of the motor. > 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. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: Michael A. Terrell on 14 May 2010 20:49 Mark Allread wrote: > > And there you have it. I work with cabling in a TV station, requiring no > more than a dozen pieces done at any given time, and you work with small > wiring inside a chassis on an assembly line, doing hundreds. Each > function has its own equipment needs. > > But a butane lighter - especially the "jet" types that behave like tiny > brazing torches - will flame downward well enough, unless they're built > to draw fuel only while upright. > > I removed the "Hot air" tip from a butane soldering iron once, and found > it even faster than the lighter, but it required more care in use. If > one tipped it the wrong way, the flame would flare due to it drawing > liquid instead of gas butane. I used a lot of clear heatshrink to label cables for TV stations and CATV headends. I preferred to label it before it was inside a rack, whenever possible. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: PeterD on 14 May 2010 20:50 On Fri, 14 May 2010 10:11:37 -0700 (PDT), "larry moe 'n curly" <larrymoencurly(a)my-deja.com> wrote: > > > >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. Well, if the diode fails in short mode, you will have only high heat. If it fails in open mode, you'll have a switch that is off-off-low!
From: larry moe 'n curly on 14 May 2010 22:22
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 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. |