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Jeff Liebermann <jeffl@cruzio.com>: Feb 09 10:29AM -0800 On Tue, 9 Feb 2016 11:23:24 -0000 (UTC), Cursitor Doom >just component leads? Most of the stuff I work on is at *least* 25 years >old and things start to get fragile. >thanks   My advice tends to go against conventional wisdom and some of the other advice in this thread. The problem is that you're delivering too many joules for too long a time (Joules = watt-seconds). To avoid problems, you have to work fast. You can get the joint as hot as you want, but not for very long.   Therefore, I suggest: 1. Don't use this type of soldering iron: <http://stellartechnical.com/images/213.jpg> 2. Use an 850F solder tip, not 750F. Work fast. 3. Use a medium size tip. Too big and it will deliver too many joules. Too small and de-soldering will take too long. 4. Don't mix lead free and Pb-Sn solder. 5. Don't use solder wick. A solder sucker works faster. 6. Hit the connection with some solder before unsoldering to make the old solder flow. Slopping flux on the pad doesn't help because the flux will vaporize before the solder melts. 7. If the PCB is phenolic, the pads always lift.   I'm undecided if hot air desoldering is any better than a soldering sucker for through hole parts.   Conformal coatings such as urethane or acrylic, will either burn or vaporize before the solder melts. Using these to glue down the pad doesn't seem to work for me.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

"Ian Field" <gangprobing.alien@ntlworld.com>: Feb 09 06:51PM "John-Del" <ohger1s@aol.com> wrote in message news:d227f504-89c1-4d6e-bed2-79397429db9b@googlegroups.com...   > Preheat the board before desoldering and apply some liquid flux. Make > sure to use *enough* heat as too low is just as bad as too much. You want > to reduce the time it takes to finish the process more than anything.   I'd add to that; make sure the end of the lead isn't bent so it struggles when you try to pull it out.   Although its my preferred method, I'm reluctant to recommend a piston type solder sucker because the recoil can knock pads off if you're not careful. Conversely; solder wick has to be kept hot while you pull it away, or the pad/track comes with it - which doesn't really help with keeping the heating to the shortest time possible.   Sometimes you have to remove the solder to inspect the end of the lead, and straighten it if required. All I can suggest is; use the method you're most comfortable with.   A single sided board is dead easy if you remove the solder, through hole takes a little more effort. Some manufacturers do sucker irons where the tip is hollow and has a receptacle for the waste solder, the expensive ones with an electric pump or the cheaper type with a rubber bulb next to the handle. It almost never removes *ALL* the solder from a through hole, but you can usually wiggle the lead free with pointy nose pliers.   In most cases more solder and the flux that comes with it is added to improve heat flow - in the case of RoHS solder, adding some 60/40 lowers the melting temperature.

John Robertson <spam@flippers.com>: Feb 09 11:25AM -0800 On 02/09/2016 4:14 AM, John-Del wrote: >> old and things start to get fragile.   >> thanks   > Preheat the board before desoldering and apply some liquid flux. Make sure to use *enough* heat as too low is just as bad as too much. You want to reduce the time it takes to finish the process more than anything.   I constantly am working on boards that are from the 1970s. Mostly I use a #7 tip on my Weller solder station, and a Soldapullt (sp?) solder sucker. Take great care not to push down on the solder pad, press the tip sideways. Do NOT let the solder sucker strike the tip when sucking the solder, but keep it on a 45 degree angle away from the tip, with its tip resting on the PCB.   Have the PCB well supported if possible so it doesn't bounce.   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

Jon Elson <jmelson@wustl.edu>: Feb 09 02:38PM -0600 Cursitor Doom wrote:   > try to de-solder a part on an elderly board and end up removing more than > just component leads? Most of the stuff I work on is at *least* 25 years > old and things start to get fragile. OY! It depends a lot on the quality of the board, and then how much heat it has been exposed to, over its life.   If the chip is no good, I scribe the leads with an X-acto knife, running down the whole row, and then JUST BARELY snap the leads off from the body. You only have to do this on one side of a SOIC. Then scribe the other side and bend the IC up and down a few times, until it breaks off completely. Then, the individual leads can be removed in a much more gentle fashion. Avoid pressing down on the pads, they will tend to "crumple" and the edges pull up from the board.   Since you say OVER 25 years, I'm guessing none of this is SMT? If it has plated through holes, these generally are quite robust. The worst are some old paper-phenolic one-sided boards. You just look at them and the pads start coming off.   There are mass desoldering tools for DIP and SOIC standard sizes that work pretty well to melt the solder on all leads simultaneously. These work great if you have the right size. I've even made some custom ones out of solid copper bar when I had a bunch of chips to pull.   And, of course, a temperatur-controlled soldering iron, run at the minimum temperature possible, is a big help.   Jon

Jon Elson <jmelson@wustl.edu>: Feb 09 02:44PM -0600 John Robertson wrote:   > Soldapullt (sp?) solder > sucker.   These work, but if you have ever used a Pace desoldering station with either a vacuum pump or a venturi suction generator, you will be AMAZED at how much better a job it does. These have a hollow copper tip, so you can keep the tip on the joing while it applies the suction. You apply the tip, wait a few seconds and then wiggle the tip in an orbiting motion and step on the pedal. When the slurping sound stops, all the solder is gone, let up on the pedal and remove the tip. There is no big reaction from a flying piston as with the plugner-type solder puller, and you get enough suction time to get ALL the solder out of the joint.   (Other brands of pump-type desoldering irons are probably just as good, but I happen to have Pace brand gear.)   Jon

"Ian Field" <gangprobing.alien@ntlworld.com>: Feb 09 08:52PM "Jon Elson" <jmelson@wustl.edu> wrote in message news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com... > has been exposed to, over its life.   > If the chip is no good, I scribe the leads with an X-acto knife, running > down the whole row, and then JUST BARELY snap the leads off from the body.   A Swan & Mortem scalpel is a little more precise for the smaller ICs, Usually I shear the pins off at the header - but you have to be careful not to slice tracks underneath.   With the old standard pitch DIL packages, a decent quality pair of side cutters were sufficient to nip the pins off flush with the header.

"Gareth Magennis" <sound.service@btconnect.com>: Feb 09 08:52PM "Jon Elson" wrote in message news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...   Cursitor Doom wrote:   > try to de-solder a part on an elderly board and end up removing more than > just component leads? Most of the stuff I work on is at *least* 25 years > old and things start to get fragile. OY! It depends a lot on the quality of the board, and then how much heat it has been exposed to, over its life.   If the chip is no good, I scribe the leads with an X-acto knife, running down the whole row, and then JUST BARELY snap the leads off from the body. You only have to do this on one side of a SOIC. Then scribe the other side and bend the IC up and down a few times, until it breaks off completely. Then, the individual leads can be removed in a much more gentle fashion. Avoid pressing down on the pads, they will tend to "crumple" and the edges pull up from the board.                 I still use a similar method when it suits. Get a new blade in your knife, and you can quite easily cut vertically through all the pins on any sized DIL (or SMD) device with no damage to the PCB, with a bit of practice of course.   (Some SMD devices are glued quite hard to the PCB, making desoldering a nightmare, but once they have no legs you can safely chisel the body off the board and wipe away the legs individually)     Gareth.

"Ian Field" <gangprobing.alien@ntlworld.com>: Feb 09 09:10PM "Gareth Magennis" <sound.service@btconnect.com> wrote in message news:Xjsuy.834766$QP2.201595@fx42.am4... > Get a new blade in your knife, and you can quite easily cut vertically > through all the pins on any sized DIL (or SMD) device with no damage to > the PCB, with a bit of practice of course.   There's a bit of a knack to it, you carve through the pins at a slight angle and make sure the blade edge lands squarely on the PCB underneath without any sliding/slicing motion.   If you avoided using too much force, any tracks underneath usually survive unscathed.   One trick I've heard about, is to feed some thin wire under an SMD chip and ease it out sideways while applying heat, lifting the pins as it goes - but this doesn't exactly fit in with the advice to minimise the duration of applied heat. It probably wouldn't help at all if the pads are fragile to start with.

John Robertson <spam@flippers.com>: Feb 09 01:14PM -0800 On 02/09/2016 12:44 PM, Jon Elson wrote:   > (Other brands of pump-type desoldering irons are probably just as good, but > I happen to have Pace brand gear.)   > Jon   I HAVE a Pace Desoldering station (actually two of them) - however I am usually just removing one or two ICs and I can remove them with my Weller (#7!) and Soldapullt faster than the Pace will heat up!   You can get a nice rhythm going where you heat two leads at the same time (medium tip) and suck both together, then while the next pair are warming up you are reloadng the sucker with your other hand. I can pull a 40 pin chip in a minute or less typically (not that I ever time myself, it just seems to go pretty fast.).   Once the legs are unsoldered I then use a tiny screwdriver to push the bottom leads back and forth across the feed through hole. If it appears to be stuck I put a dab of solder and resuck. Then I press the bottom of each leg on the top side where they meet the PCB to again loosen them up. At this point the IC usually pulls out with my finger tips. Prying with any force at all means something is wrong...not to mention it yanks out feed through pipes!   If I am reworking a bunch of chips then the Pace is heated up. It is slightly better as you can put the tip around the IC's lead and swirl it from side to side as you heat it up, to feel if it has released, prior to suction.   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

Jon Elson <jmelson@wustl.edu>: Feb 09 04:29PM -0600 John Robertson wrote:     > I HAVE a Pace Desoldering station (actually two of them) - however I am > usually just removing one or two ICs and I can remove them with my > Weller (#7!) and Soldapullt faster than the Pace will heat up!   Yes, this is absolutely true! But, for something really expensive, or where I have a lot of pins to desolder, I take the time to warm up the Pace, and always get GREAT results. Usually the part just falls off the board when the last pin is desoldered.   > Once the legs are unsoldered I then use a tiny screwdriver to push the > bottom leads back and forth across the feed through hole. If it appears > to be stuck I put a dab of solder and resuck. With the Pace, and the technique of orbiting the tip while applying suction, I RARELY have this happen. Usually, I desolder the whole chip and it just falls off the board. That wigglign back and forth can damage the plated barrel of the hole.   Jon

"Gareth Magennis" <sound.service@btconnect.com>: Feb 10 12:08AM "Ian Field" wrote in message news:QAsuy.601143$pB6.586499@fx41.am4...       "Gareth Magennis" <sound.service@btconnect.com> wrote in message news:Xjsuy.834766$QP2.201595@fx42.am4... > Get a new blade in your knife, and you can quite easily cut vertically > through all the pins on any sized DIL (or SMD) device with no damage to > the PCB, with a bit of practice of course.   There's a bit of a knack to it, you carve through the pins at a slight angle and make sure the blade edge lands squarely on the PCB underneath without any sliding/slicing motion.   If you avoided using too much force, any tracks underneath usually survive unscathed.         Yep, that's my method exactly. More of a Guillotine action.     Gareth.

Bob Engelhardt <BobEngelhardt@comcast.net>: Feb 09 08:07PM -0500 Has anyone ever used pressure to blow away solder? I'm thinking that 125 psi through a tiny nozzle would clean out the solder better than a spring loaded solder sucker.   Though I guess that it might send molten solder where you don't want it!   Bob

Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Feb 10 03:18AM +0100 On 10.02.16 2:07, Bob Engelhardt wrote: > spring loaded solder sucker.   > Though I guess that it might send molten solder where you don't want it!   > Bob   It WILL send it all over the place. Nice way though to destroy a board.......

John Robertson <spam@flippers.com>: Feb 09 10:46PM -0800 On 02/09/2016 2:29 PM, Jon Elson wrote: > falls off the board. That wigglign back and forth can damage the plated > barrel of the hole.   > Jon   When you are 'orbiting' I take that to mean that you are applying side pressure to the leg of the device to move it far enough away from the walls of the tube that the solder is removed completely and the leg has no sticking point to the tube. That is the same process I use.   I just like using the Soldapullt, it is faster and when done with a bit of experience (35 years in my case) gives very good consistent results when extracting one or two ICs at a time. I train students to use the Soldapullt in under a week - give them some bunged up boards to learn how to remove parts without damaging the parts or the PCB. They learn quickly and most can do a good job with only a day or so of practice.   When they get good with the Soldapullt I then train them on the Pace!   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

frank <frank@invalid.net>: Feb 10 11:29AM > 125 psi through a tiny nozzle would clean out the solder better than a > spring loaded solder sucker.   > Though I guess that it might send molten solder where you don't want it!   I tried that once on a board that was hopeless and marked for "spare parts" only. When blowing from the bottom side, the ICs would come out full of solder residuals on the bottom side (cleaning required a longer time than using a proper desolder method). When blowing from the upper side (IC side), the action was not so effective in removing all the solder from the hole and anyway the solder residues were blown everywhere in the bench. In short, I've never tried that again.   Frank IZ8DWF

John-Del <ohger1s@aol.com>: Feb 10 04:41AM -0800 On Tuesday, February 9, 2016 at 1:29:13 PM UTC-5, Jeff Liebermann wrote:   > 6. Hit the connection with some solder before unsoldering to make the > old solder flow. Slopping flux on the pad doesn't help because the > flux will vaporize before the solder melts.     Adding fresh solder adds flux assuming you are using a flux core solder. While the carrier will vaporize, the flux solids remain. I always deflux when the repair is completed.     > I'm undecided if hot air desoldering is any better than a soldering > sucker for through hole parts.   Not sure either, but I often use hot air to preheat the area before using the iron. Nothing ruins desoldering faster than heat sinking.

Julian Barnes <jb9889@notformail.com>: Feb 10 01:35PM On Wed, 10 Feb 2016 04:41:37 -0800, John-Del wrote:   > Not sure either, but I often use hot air to preheat the area before > using the iron. Nothing ruins desoldering faster than heat sinking.   And nothing ruins germanium semis faster than NOT heat sinking.

John-Del <ohger1s@aol.com>: Feb 10 06:59AM -0800 On Wednesday, February 10, 2016 at 8:38:54 AM UTC-5, Julian Barnes wrote:   > > Not sure either, but I often use hot air to preheat the area before > > using the iron. Nothing ruins desoldering faster than heat sinking.   > And nothing ruins germanium semis faster than NOT heat sinking.   Not sure of your point, but what I'm referring to is the heat sink action of a multi layer PC with a huge ground plane running on or in it. Placing a soldering tip on some points can actually freeze the tip to the joint in worse cases, or prevent complete solder melting inside a plated through hole. Anybody who has replaced an IPM on an LG sustain board can attest to this. Preheating the board minimizes excessive loss of desoldering tip heat to surrounding areas.

Chuck <chuck@mydeja.net>: Feb 10 09:18AM -0600 On Tue, 9 Feb 2016 21:10:14 -0000, "Ian Field" >this doesn't exactly fit in with the advice to minimise the duration of >applied heat. It probably wouldn't help at all if the pads are fragile to >start with.   I used to use this technique. Usually on 64 pin or more chips at least one trace would lift.   --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

Jon Elson <jmelson@wustl.edu>: Feb 03 03:27PM -0600 Tim R wrote:     > I got a better look yesterday. It's a street light, no camera. Besides, > I see the flash when I'm stopped at a red light, so the cross traffic > would have a green.   It is a worn-out lamp. When they get old, they start to run hot and the ballast cycles power every few minutes. The repeated starting, maybe 10 times an hour, increases the wear on the lamp. When they get really bad, the ignitor can't strike the arc, and so the ignitor keeps trying. The strobe effect, maybe a couple flashes a second, is the ignitor trying to get the lamp to restart.   Jon

N_Cook <diverse@tcp.co.uk>: Jan 31 11:44AM Back to perfect working order. Quite a bit of space in there but no 100nF 400V(decided to up from 250V rating) cap laying around, but 4x .47uF 100V in series went in there with room to spare. This will be a stock fault with these nice compact drills, I use mine on a daily basis it seems. While in there a better idea of anti-vibration fudge for the pot knob, simply a small O ring over the pot shaft, before replacing the knob, to bind slightly as it is compressed slightly when fitted in the casing. I left the TIC226 triac in there as running perfectly normally.

enriqeemilojimenez@gmail.com: Feb 09 01:59PM -0800 On Wednesday, October 29, 2008 at 6:23:50 AM UTC-4, Sparkey wrote:

Reinhard Zwirner <reinhard.zwirner@t-online.de>: Feb 09 07:07PM +0100 William Cox schrieb:   > Am trying to fix a Tek 2215A with the delayed sweep not functioning properly. > I am able to see both A and B sweeps but am unable to use the B Time delay position.   > Anyone have an idea?   Here   <https://groups.yahoo.com/neo/groups/TekScopes/conversations/topics>   you'll find the real experts!   HTH   Reinhard

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