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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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the REAL problem with my Dustbuster...
The actual problem was not an intermittent switch. It was the last thing I'd
have expected -- one of the welds on the battery pack had come loose! Without turning this into a megillah... Any suggestions on repairing it without damaging the cell? I don't have welding equipment. I do have an EDSYN pencil iron, and a 100W RadioShack gun. Please don't turn a straightforward question into a tsimmes. (But you will.) -- "We already know the answers -- we just haven't asked the right questions." -- Edwin Land |
#2
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the REAL problem with my Dustbuster...
In article ,
"William Sommerwerck" wrote: The actual problem was not an intermittent switch. It was the last thing I'd have expected -- one of the welds on the battery pack had come loose! Without turning this into a megillah... Any suggestions on repairing it without damaging the cell? I don't have welding equipment. I do have an EDSYN pencil iron, and a 100W RadioShack gun. Please don't turn a straightforward question into a tsimmes. (But you will.) The Edsyn will work. Didn't we just have a thread on soldering to batteries? Maybe that was on a.h.r. Clean surfaces. Scuff with sandpaper. Use liquid flux. Crank Edsyn up to 800F. Tin wire. Tin battery. Use more flux and reflow wire to battery. |
#3
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the REAL problem with my Dustbuster...
On Tue, 8 Mar 2011 18:34:44 -0800, "William Sommerwerck"
wrote: The actual problem was not an intermittent switch. It was the last thing I'd have expected -- one of the welds on the battery pack had come loose! It happens. Spot welding takes practice. Without turning this into a megillah... Any suggestions on repairing it without damaging the cell? I don't have welding equipment. I do have an EDSYN pencil iron, and a 100W RadioShack gun. Test the broken flat wire to see if it can be soldered. Keep the battery as cold as possible (i.e. wet sponge). Plenty of liquid flux and heat. Work fast to keep the heat affected zone to a minimum. Please don't turn a straightforward question into a tsimmes. (But you will.) Mazel Tov. You can also build your own spot welder with a big fat cazapitor. Search Google and YouTube for "capacitor discharge spot welder". For example: http://forum.allaboutcircuits.com/showthread.php?t=24385 If you don't want to build the entire circuit, just charge up the biggest capacitor bank you can throw together. One lead goes to the battery terminal. The flat wire goes is placed on top of the terminal. The electrode is some kind of heavy (#10 awg) solid copper wire. Compress this sandwich together, and apply power at the capacitor bank. Hopefully, it will weld the flat wire, and not the capacitor terminals. In theory, the stainless leads with have a higher resistance than the copper electrodes, so the stainless will heat up, not the copper. Last resort is to drag it down to Batteries Plus or some similar vendor that has the proper spot welder. Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#4
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the REAL problem with my Dustbuster...
Jeff Liebermann wrote:
On Tue, 8 Mar 2011 18:34:44 -0800, "William Sommerwerck" wrote: The actual problem was not an intermittent switch. It was the last thing I'd have expected -- one of the welds on the battery pack had come loose! It happens. Spot welding takes practice. Without turning this into a megillah... Any suggestions on repairing it without damaging the cell? I don't have welding equipment. I do have an EDSYN pencil iron, and a 100W RadioShack gun. .... Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. There is a conductive epoxy that can be used to fix this sort of thing... John :-#)# -- (Please post followups or tech enquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
#5
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the REAL problem with my Dustbuster...
The Edsyn will work. Didn't we just have a thread
on soldering to batteries? Yes. But I like to double-check. Maybe that was on a.h.r. Clean surfaces. Scuff with sandpaper. Use liquid flux. Crank Edsyn up to 800F. Tin wire. Tin battery. Use more flux and reflow wire to battery. Pretty much what I thought. Thanks. |
#6
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the REAL problem with my Dustbuster...
Keep the battery as cold as possible (i.e. wet sponge).
Hadn't thought of that. I could stick it in the refrigerator for a while, too.l You can also build your own spot welder with a big fat cazapitor. Great! A man after my intellectual heart. Search Google and YouTube for "capacitor discharge spot welder". For example: http://forum.allaboutcircuits.com/showthread.php?t=24385 If you don't want to build the entire circuit, just charge up the biggest capacitor bank you can throw together. I've got some electronic-flash caps lying around. Last resort is to drag it down to Batteries Plus or some similar vendor that has the proper spot welder. I never thought of that! It might be worth a coupla bucks! Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. Unless it's silver-filled epoxy, no way. |
#7
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the REAL problem with my Dustbuster...
There is a conductive epoxy that can be used
to fix this sort of thing... I invented conductive epoxy 50+ years ago. I didn't patent it, though. And probably someone else had beaten me to it. |
#8
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the REAL problem with my Dustbuster...
Jeff Liebermann wrote:
On Tue, 8 Mar 2011 18:34:44 -0800, "William Sommerwerck" wrote: The actual problem was not an intermittent switch. It was the last thing I'd have expected -- one of the welds on the battery pack had come loose! It happens. Spot welding takes practice. Without turning this into a megillah... Any suggestions on repairing it without damaging the cell? I don't have welding equipment. I do have an EDSYN pencil iron, and a 100W RadioShack gun. Test the broken flat wire to see if it can be soldered. Keep the battery as cold as possible (i.e. wet sponge). Plenty of liquid flux and heat. Work fast to keep the heat affected zone to a minimum. Please don't turn a straightforward question into a tsimmes. (But you will.) Mazel Tov. You can also build your own spot welder with a big fat cazapitor. Search Google and YouTube for "capacitor discharge spot welder". For example: http://forum.allaboutcircuits.com/showthread.php?t=24385 If you don't want to build the entire circuit, just charge up the biggest capacitor bank you can throw together. One lead goes to the battery terminal. The flat wire goes is placed on top of the terminal. The electrode is some kind of heavy (#10 awg) solid copper wire. Compress this sandwich together, and apply power at the capacitor bank. Hopefully, it will weld the flat wire, and not the capacitor terminals. In theory, the stainless leads with have a higher resistance than the copper electrodes, so the stainless will heat up, not the copper. Spot welding is a LOT harder than it sounds. Just to use some round numbers that you can scale for your application... If you expect to get 10,000 amps out of 10V, you can't have more than a milliohm of resistance. That's the cap esr + the switch + the wire + the contacts + the contact resistance at the weld. And the only thing that does much good is the amps x volts x time at the junction between the two parts being welded plus a little in the weld material itself. An extra couple of milliohms in the system will render the welder impotent. And the weld will be extremely sensitive to the contact resistance between the weldments and thus the pressure applied and the contact area and, and , and. With a low-voltage AC welder made from a microwave oven transformer, I was getting about 20% good welds. The commercial CD welder with the same homebrew weld head was closer to 100% good. You really want something that controls current rather than voltage. Then, most of the variables end up in one place, the weld. Using a higher voltage and some intentional, controlled series resistance can make it much more reliable. Many battery tabs are made of zinc. Easier to weld than stainless. Hobby-Store 5mil brass is very easy to weld, but may be too high resistance for a dust buster. Having said that, you can, with practice, make usable battery tab welds with a capacitor bank, a pressure controlled contact system and a switch made out of a nail. Charge the caps, apply weld pressure, slam the nail across two BIG wires. I was using 4/0 wire. You get one weld per nail, but nails are cheap. You didn't say which wire. if it's the negative, you may be able to fix it by hose-clamping the wire to the battery case. I'm gonna get yelled at, but I would not solder a battery. Can be done with practice. Trying it for the first time on the only battery you have is fraught with risk. Separator material inside melts pretty easily. I wouldn't try with a gun. I'd use a 50W pencil with a MASSIVE 1000F tip and very short heat application. You're heating a lot of mass quickly. Gun can't hack it. YMMV Last resort is to drag it down to Batteries Plus or some similar vendor that has the proper spot welder. Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. |
#9
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the REAL problem with my Dustbuster...
I'm gonna get yelled at, but I would not solder a battery.
Can be done with practice. I remember successfully doing it once or twice before. But you're right -- it's not a good idea. Solder doesn't bond well with most battery cases, and the case is huge heat sink that makes it hard to make a quick solder joint. Trying it for the first time on the only battery you have is fraught with risk. Charlie Fraught and Joe Risk? Last resort is to drag it down to Batteries Plus or some similar vendor that has the proper spot welder. I lucked out. The guy at the local B+ store said he'd do it for free if I came in early tomorrow morning. |
#10
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the REAL problem with my Dustbuster...
On Wed, 9 Mar 2011 03:58:33 -0800, "William Sommerwerck"
wrote: Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. Unless it's silver-filled epoxy, no way. I don't mean slopping the epoxy in between the battery terminal and the flat wire. I mean push the two wires together, and slop some epoxy on top in order to just hold them together. The Dustbuster doesn't draw all that much current so I suspect a simple mechanical connection will work. Kinda like the contacts for D cell batteries in kids toys, flashlights, games, etc, where a welded contact isn't necessary. If you're not sure if it will work, and don't want to deal with permanent epoxy, use Duct Tape to hold the flat wire in place. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#11
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the REAL problem with my Dustbuster...
On Wed, 09 Mar 2011 08:16:00 -0800, mike wrote:
Spot welding is a LOT harder than it sounds. I agree. I spent about 5 days tinkering with mine trying to get it right. Every time I added more capacitance, things improved. The basic trick is to make sure the resistance of the joint to be welded, is higher than all the other resistances (and ESR of the capacitor). Mine currently has two 3F 20v caps in parallel. Something like this: http://ledhacks.com/power/battery_tab_welder.htm Just to use some round numbers that you can scale for your application... If you expect to get 10,000 amps out of 10V, you can't have more than a milliohm of resistance. That's the cap esr + the switch + the wire + the contacts + the contact resistance at the weld. And the only thing that does much good is the amps x volts x time at the junction between the two parts being welded plus a little in the weld material itself. Good point. However, I have no way to measure the peak current or the current necessary to do the weld. I just kept adding capacitance until it worked. An extra couple of milliohms in the system will render the welder impotent. And the weld will be extremely sensitive to the contact resistance between the weldments and thus the pressure applied and the contact area and, and , and. Well, the idea is to dissipate the power in the connection, not in the capacitors, SCR, or contacts. As long as the capacitor is huge, the SCR oversized, wires beefy, and the contacts can handle both the current and the heat, it should work. With a low-voltage AC welder made from a microwave oven transformer, I was getting about 20% good welds. The commercial CD welder with the same homebrew weld head was closer to 100% good. Apples and oranges. There's enough resistance in the transformer winding to probably make the welder useless. If the primary winding was made from copper buss bars, it might have a chance, but not a copper wire wound xformer. A big capacitor has an internal resistance, but that's MUCH less than the resistance of a wired transformer winding. You really want something that controls current rather than voltage. Then, most of the variables end up in one place, the weld. Using a higher voltage and some intentional, controlled series resistance can make it much more reliable. Agreed. Voltage doesn't matter. It's the current that does the heating. If you shove XX Amps through YY ohms of resistance, it's going to heat I^2*R (Ohms Law). Whatever voltage it took to deliver that much current is largely irrelivent. Many battery tabs are made of zinc. Easier to weld than stainless. Hobby-Store 5mil brass is very easy to weld, but may be too high resistance for a dust buster. I haven't seen any zinc tabs yet. I've seen tin plated steel and stainless. Brass should work for a Dustbuster as they don't draw all that much current. Having said that, you can, with practice, make usable battery tab welds with a capacitor bank, a pressure controlled contact system and a switch made out of a nail. Charge the caps, apply weld pressure, slam the nail across two BIG wires. I was using 4/0 wire. You get one weld per nail, but nails are cheap. I used a copper contact knife switch. I welded the contacts a few times, but was able to break it apart, file it clean, and do it again. One more idea. Single sided resitance spot welder as used in auto body shops. http://www.jcwhitney.com/spot-welder/p2007539.jcwx However, you'll need an arc welder for this to work. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#12
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the REAL problem with my Dustbuster...
On Wed, 09 Mar 2011 16:42:48 -0800, Jeff Liebermann
wrote: I haven't seen any zinc tabs yet. I've seen tin plated steel and stainless. Also flat wire made from nickel or various nickel alloys, which is difficult, but not impossible to solder. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#13
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the REAL problem with my Dustbuster...
Very last resort is to just slop some epoxy on the flat wire and
battery terminal, and hope that it holds. Unless it's silver-filled epoxy, no way. I don't mean slopping the epoxy in between the battery terminal and the flat wire. I mean push the two wires together, and slop some epoxy on top in order to just hold them together. The Dustbuster doesn't draw all that much current so I suspect a simple mechanical connection will work. Kinda like the contacts for D cell batteries in kids toys, flashlights, games, etc, where a welded contact isn't necessary. But there's a spring applying pressure. If you're not sure if it will work, and don't want to deal with permanent epoxy, use Duct Tape to hold the flat wire in place. The problem (from my point of view) is oxidation. I figure the Dustbuster draws ~1amp, so I need a clean, tight, connection. Regardless, I'm going to have it welded tomorrow morning. |
#14
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the REAL problem with my Dustbuster...
William Sommerwerck wrote:
Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. Unless it's silver-filled epoxy, no way. I don't mean slopping the epoxy in between the battery terminal and the flat wire. I mean push the two wires together, and slop some epoxy on top in order to just hold them together. The Dustbuster doesn't draw all that much current so I suspect a simple mechanical connection will work. Kinda like the contacts for D cell batteries in kids toys, flashlights, games, etc, where a welded contact isn't necessary. But there's a spring applying pressure. If you're not sure if it will work, and don't want to deal with permanent epoxy, use Duct Tape to hold the flat wire in place. The problem (from my point of view) is oxidation. I figure the Dustbuster draws ~1amp, so I need a clean, tight, connection. You should measure it. I was too lazy to get out the big power supply, but 3A would hardly get mine started. I've replaced the batteries in mine twice and finally gave up. The load current is very hard on batteries. Especially since people don't stop when it slows down. They just keep on trucking pumping 5A backwards into the weakest cell. And the constant current charge 24/7 is also very hard on the battery. Bad design. Regardless, I'm going to have it welded tomorrow morning. |
#15
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the REAL problem with my Dustbuster...
Jeff Liebermann wrote:
On Wed, 09 Mar 2011 08:16:00 -0800, mike wrote: Spot welding is a LOT harder than it sounds. I agree. I spent about 5 days tinkering with mine trying to get it right. Every time I added more capacitance, things improved. The basic trick is to make sure the resistance of the joint to be welded, is higher than all the other resistances (and ESR of the capacitor). Mine currently has two 3F 20v caps in parallel. Something like this: http://ledhacks.com/power/battery_tab_welder.htm Interesting. Those welds are way better than anything I could get using a microwave transformer and handheld electrodes. Spring loaded parallel electrodes jigged to an arbor press improved things dramatically. Just to use some round numbers that you can scale for your application... If you expect to get 10,000 amps out of 10V, you can't have more than a milliohm of resistance. That's the cap esr + the switch + the wire + the contacts + the contact resistance at the weld. And the only thing that does much good is the amps x volts x time at the junction between the two parts being welded plus a little in the weld material itself. Good point. However, I have no way to measure the peak current or the current necessary to do the weld. I just kept adding capacitance until it worked. Yep, at the time I did the experiments, I didn't have a digital storage scope or anything that could measure 10,000 amps. My welds got dramatically better about 10 minutes after I got the DSO and could study what was happening. An extra couple of milliohms in the system will render the welder impotent. And the weld will be extremely sensitive to the contact resistance between the weldments and thus the pressure applied and the contact area and, and , and. Well, the idea is to dissipate the power in the connection, not in the capacitors, SCR, or contacts. As long as the capacitor is huge, the SCR oversized, wires beefy, and the contacts can handle both the current and the heat, it should work. Yes, but... CONTROL is critical. Some tiny resistance in the path makes the current in the weld slightly less dependent on the contact resistance. When dumping a cap into the weld, I found that the a small difference in electrode pressure made the difference between no weld at all and a hole in the tab...and no weld at all. Keeping it in the sweet spot was tough. With a low-voltage AC welder made from a microwave oven transformer, I was getting about 20% good welds. The commercial CD welder with the same homebrew weld head was closer to 100% good. Apples and oranges. There's enough resistance in the transformer winding to probably make the welder useless. If the primary winding was made from copper buss bars, it might have a chance, but not a copper wire wound xformer. A big capacitor has an internal resistance, but that's MUCH less than the resistance of a wired transformer winding. Your apples must be different from my apples. My transformer had a two turn secondary of copper wire an inch in diameter...4/0 wire if I remember correctly. I carefully controlled an integral number of full cycles of 120VAC into the primary. Took about six cycles to weld. Primary current was about 30A and made the house hum on a 15A breaker. I'd like to measure the current profile of some of the homebrew welders linked from this thread. No way a 50 amps is gonna be useful. People get away with a 50A SCR in the secondary only because the single-pulse peak current rating is WAY bigger than 50A. I've been using a 40A SSR on the primary side. You really want something that controls current rather than voltage. Then, most of the variables end up in one place, the weld. Using a higher voltage and some intentional, controlled series resistance can make it much more reliable. Agreed. Voltage doesn't matter. It's the current that does the heating. If you shove XX Amps through YY ohms of resistance, it's going to heat I^2*R (Ohms Law). Whatever voltage it took to deliver that much current is largely irrelivent. Yes, as long as you can control the current. Some resistance in the path makes the current less dependent on the resistance at the weld. You trade significant wasted energy for repeatability. Many battery tabs are made of zinc. Easier to weld than stainless. Hobby-Store 5mil brass is very easy to weld, but may be too high resistance for a dust buster. I haven't seen any zinc tabs yet. I've seen tin plated steel and stainless. Brass should work for a Dustbuster as they don't draw all that much current. Might want to measure that current. As I recall, mine was over 5A. The weld current profile can also be important. You need to match the energy in with the thermal time constant. A capacitor has peak current at the time the contact resistance is highest. The advantage of a dual-pulse welder is that the first pulse normalizes the contact resistance somewhat. And with some effort, you can use the voltage/current profile of the first pulse to match the characteristics of the second pulse to a specific weld instance. My CD welder claims to be able to put 7V into a milliohm. They dump the cap into the primary of a transformer. That inductance gives the current profile a softer start and spreads the energy out over a few milliseconds. Having said that, you can, with practice, make usable battery tab welds with a capacitor bank, a pressure controlled contact system and a switch made out of a nail. Charge the caps, apply weld pressure, slam the nail across two BIG wires. I was using 4/0 wire. You get one weld per nail, but nails are cheap. I used a copper contact knife switch. I welded the contacts a few times, but was able to break it apart, file it clean, and do it again. One more idea. Single sided resitance spot welder as used in auto body shops. http://www.jcwhitney.com/spot-welder/p2007539.jcwx However, you'll need an arc welder for this to work. That ain't gonna work. The manual says hold it for 2 seconds. the battery will be toast by then. And you have zero control over what's happening. You can't wait for a battery weld to turn red. |
#16
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the REAL problem with my Dustbuster...
On Wed, 9 Mar 2011 17:03:31 -0800, "William Sommerwerck"
wrote: Very last resort is to just slop some epoxy on the flat wire and battery terminal, and hope that it holds. Unless it's silver-filled epoxy, no way. I don't mean slopping the epoxy in between the battery terminal and the flat wire. I mean push the two wires together, and slop some epoxy on top in order to just hold them together. The Dustbuster doesn't draw all that much current so I suspect a simple mechanical connection will work. Kinda like the contacts for D cell batteries in kids toys, flashlights, games, etc, where a welded contact isn't necessary. But there's a spring applying pressure. Bend the flat wire over a few times and you'll get some spring pressure. If you're not sure if it will work, and don't want to deal with permanent epoxy, use Duct Tape to hold the flat wire in place. The problem (from my point of view) is oxidation. I figure the Dustbuster draws ~1amp, so I need a clean, tight, connection. Apply duct tape for contact pressure. Bury the battery pack in cellophane wrap for water, dust, and debris proofing. Regardless, I'm going to have it welded tomorrow morning. Too easy but good luck anyway. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#17
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the REAL problem with my Dustbuster...
You really want something that controls current rather than
voltage. Then, most of the variables end up in one place, the weld. Using a higher voltage and some intentional, controlled series resistance can make it much more reliable. Agreed. Voltage doesn't matter. It's the current that does the heating. If you shove XX Amps through YY ohms of resistance, it's going to heat I^2*R (Ohms Law). Whatever voltage it took to deliver that much current is largely irrelivent. Same basic principle as electrocution. |
#18
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the REAL problem with my Dustbuster...
The problem (from my point of view) is oxidation. I figure the Dustbuster
draws ~1amp, so I need a clean, tight, connection. You should measure it. I was too lazy to get out the big power supply, but 3A would hardly get mine started. I've replaced the batteries in mine twice and finally gave up. The load current is very hard on batteries. Especially since people don't stop when it slows down. They just keep on trucking pumping 5A backwards into the weakest cell. And the constant current charge 24/7 is also very hard on the battery. Bad design. This is why I always run it at High (which uses all the cells), and stop a bit after the motor starts to slow down. As a result, the battery pack is in excellent condition. |
#19
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the REAL problem with my Dustbuster...
On Wed, 9 Mar 2011 20:49:02 -0600, "Shaun" wrote:
You're an idiot to suggest epoxy. The contacts will oxidize and then there will be no connection, might take a couple of months before this happens, but it will happen. Ok, I'll bite. Stainless or Nickel oxidize? What electrolyte is in epoxy that will attack stainless steel or nickel? Meanwhile, I can buy epoxy paint, epoxy coated rebar, conductive (Aluminum doped) epoxy, epoxy covering junction coating for cheap PCB packaging, etc. I can also buy quite a few fiberglass marine hulls and decks, which are held together by epoxy and have stainless deck fittings. No corrosion warnings on any of the epoxy cans, bottles, and tubes that I can find. It's certainly not hydroscopic so there's no electrolytic action. The stainless and nickel are fairly close on the galvanic series: http://www.corrosionist.com/galvanic_corrosion_chart.htm Sigh. Where is Dr. Barry L. Ornitz when we need him? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#20
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the REAL problem with my Dustbuster...
But there's a spring applying pressure.
Bend the flat wire over a few times and you'll get some spring pressure. It's too short. And I want a "permanet" fix. |
#21
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the REAL problem with my Dustbuster...
You're an idiot to suggest epoxy. The contacts will oxidize and then
there will be no connection, might take a couple of months before this happens, but it will happen. Ok, I'll bite. Stainless or nickel oxidize? What electrolyte is in epoxy that will attack stainless steel or nickel? Meanwhile, I can buy epoxy paint, epoxy coated rebar, conductive (aluminum doped) epoxy, epoxy covering junction coating for cheap PCB packaging, etc. I can also buy quite a few fiberglass marine hulls and decks, which are held together by epoxy and have stainless deck fittings. No corrosion warnings on any of the epoxy cans, bottles, and tubes that I can find. It's certainly not hydroscopic so there's no electrolytic action. The stainless and nickel are fairly close on the galvanic series: http://www.corrosionist.com/galvanic...sion_chart.htm Sigh. Where is Dr. Barry L. Ornitz when we need him? Is this your reference? I'm not sure I see the connection (other than the general one of chemical reactions between dissimilar substances). http://www.natscience.com/Uwe/Forum....icizer-problem Basic rule -- all discussions eventually get out of hand. Another rule... If simply pressing two surfaces together made for a good electrical connection, we'd need much less solder. You've no doubt read stories about how unsoldered connections lasted a week, a month, a year -- but eventually failed. Solder creates an alloy bond that doesn't slowly deteriorate from exposure to oxygen and contaminants. Before someone mentions wire wrap... In wire wrapping, the wire actually cuts into the post, forming a gas-tight connection. |
#22
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the REAL problem with my Dustbuster...
On Thu, 10 Mar 2011 04:35:00 -0800, "William Sommerwerck"
wrote: You're an idiot to suggest epoxy. The contacts will oxidize and then there will be no connection, might take a couple of months before this happens, but it will happen. Ok, I'll bite. Stainless or nickel oxidize? What electrolyte is in epoxy that will attack stainless steel or nickel? Meanwhile, I can buy epoxy paint, epoxy coated rebar, conductive (aluminum doped) epoxy, epoxy covering junction coating for cheap PCB packaging, etc. I can also buy quite a few fiberglass marine hulls and decks, which are held together by epoxy and have stainless deck fittings. No corrosion warnings on any of the epoxy cans, bottles, and tubes that I can find. It's certainly not hydroscopic so there's no electrolytic action. The stainless and nickel are fairly close on the galvanic series: http://www.corrosionist.com/galvanic...sion_chart.htm Sigh. Where is Dr. Barry L. Ornitz when we need him? Is this your reference? I'm not sure I see the connection (other than the general one of chemical reactions between dissimilar substances). http://www.natscience.com/Uwe/Forum....icizer-problem No. That's for soft rubber. Plasticizer is what softens plastics. Quite the opposite in epoxies. However, after doing my homework AFTER posting the above, I recalled that stainless will self corrode: http://yarchive.net/electr/galvanic_corrosion.html "In an earlier post, I mentioned that the stainless alloys can galvanically corrode by themselves without the presence of a dissimilar metal. This characteristic is a property of almost all nickel alloys not just the 18-8 (400 series) and 18-8-3 (300 series) of stainless alloys. It is indeed unfortunate that these alloys were given the name "stainless" since they can often corrode under relatively mild conditions." However, that takes years, not months as the OP alleges. Basic rule -- all discussions eventually get out of hand. Yep. I consider myself part of the problem, not the solution. I also don't like being called an idiot by someone that doesn't bother to substantiate their allegations. If this discussion had remained on the original topic (Dustbuster), I would have been terminally bored and not bothered reading further. Sometimes the topic drift is more interesting than the original topic. I'm far more interested in building capacitive discharge spot welders than fixing dust busters. Another rule... If simply pressing two surfaces together made for a good electrical connection, we'd need much less solder. I guess we need to throw out all the flashlight battery designs and similar battery holders. I could probably get an adequate connection by simply pressing the flat wire to the battery terminal, and jamming it in place with an added spring, rubber block, or wad of something compressible. However, if the current drain really is 3A, not the 1A I was guessing, it probably won't last. You've no doubt read stories about how unsoldered connections lasted a week, a month, a year -- but eventually failed. Sure. Most of those failures are from corrosion. If you environmentally isolate the junction, such as burying it under a blob of epoxy (or other glue), it's unlikely to corrode. The rest are from arcing, which can be reduced by avoiding pointy contacts. Solder creates an alloy bond that doesn't slowly deteriorate from exposure to oxygen and contaminants. Yep. (Reminder: I used to design marine radios.) Before someone mentions wire wrap... In wire wrapping, the wire actually cuts into the post, forming a gas-tight connection. Yep. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#23
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the REAL problem with my Dustbuster...
Another rule... If simply pressing two surfaces together made
for a good electrical connection, we'd need much less solder. I guess we need to throw out all the flashlight battery designs and similar battery holders. I earlier made a remark about springs -- which flashlights and battery holders have in abundance. Sometimes the battery holder /is/ the spring. I just got back from Batteries Plus. The guy was courteous, and I bought some 9V batteries I needed. I reinstalled the battery, and everything is now hunky-dorey. Knowing my luck, the battery will fail tomorrow (though I doubt it). |
#24
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the REAL problem with my Dustbuster...
On Thu, 10 Mar 2011 09:58:09 -0800, "William Sommerwerck"
wrote: Another rule... If simply pressing two surfaces together made for a good electrical connection, we'd need much less solder. I guess we need to throw out all the flashlight battery designs and similar battery holders. I earlier made a remark about springs -- which flashlights and battery holders have in abundance. Sometimes the battery holder /is/ the spring. Yep. I have a few of those that use "flexible" plastic to provide the spring tension. They last about 5-10 years, until the plasticizer dries out. Then, they remain permantently deformed, or cold flow into a useless shape. I hit them with a hot air gun, and try to melt the plastic back in shape. Sometimes it works, but usually, all the tension is gone. I just got back from Batteries Plus. The guy was courteous, and I bought some 9V batteries I needed. I reinstalled the battery, and everything is now hunky-dorey. Knowing my luck, the battery will fail tomorrow (though I doubt it). Nice. Is it too late to have you measure the operating current of the Dustbuster to satisify my curiosity? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#25
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the REAL problem with my Dustbuster...
I just got back from Batteries Plus. The guy was courteous,
and I bought some 9V batteries I needed. I reinstalled the battery, and everything is now hunky-dorey. Knowing my luck, the battery will fail tomorrow (though I doubt it). Nice. Is it too late to have you measure the operating current of the Dustbuster to satisify my curiosity? It is. I've unbuttoned and rebuttoned it so many times I don't feel like doing it again. But I suspect your 3A estimate is good. The unit uses sub-C cells, and runs less than 20 minutes on high -- probably closer to 10. |
#26
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the REAL problem with my Dustbuster...
There is no cutting action in the wirewrap process.. and the post/terminal
isn't typically deformed, the wire is. The round wire surface is displaced by the corners of the post (conforms to the corners), breaking thru any surface oxidation of the surfaces, and creating the gas-tight, electrically secure mechanical connection after several/6 wraps are completed. -- Cheers, WB .............. "William Sommerwerck" wrote in message ... Before someone mentions wire wrap... In wire wrapping, the wire actually cuts into the post, forming a gas-tight connection. |
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