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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Unpotting a transformer
I picked up a 600 watt power pack for running those little sidewalk and
yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. |
#2
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Unpotting a transformer
On Apr 21, 8:51 am, RoyJ wrote:
I picked up a 600 watt power pack for running those little sidewalk and yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. If it survived the temperature while being potted, it should do the same in the reverse direction......give it a go, see what happens..........or, manually chip out enough of the gunk to get to the secondary transformer leads and hook to them... Andrew VK3BFA. |
#4
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Unpotting a transformer
Freeze it with liquid nitrogen and break the goop off (proper PPE of course). I hear they use that technique to separate rubber from metal in shredded tires. RoyJ wrote: That's what I thought at first but when you pour the goop in, the temperature drops rapidly, the core never sees the high temp. When you reverse it, the leads would see the overtemp. I can get at all the leads, I could just saw the case apart and leave it potted. wrote: On Apr 21, 8:51 am, RoyJ wrote: I picked up a 600 watt power pack for running those little sidewalk and yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. If it survived the temperature while being potted, it should do the same in the reverse direction......give it a go, see what happens..........or, manually chip out enough of the gunk to get to the secondary transformer leads and hook to them... Andrew VK3BFA. |
#5
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Unpotting a transformer
RoyJ wrote:
I picked up a 600 watt power pack for running those little sidewalk and yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. http://www.minute-man.com/acatalog/E...gnet_Wire.html Indicates a max working temp of 130C http://en.wikipedia.org/wiki/Magnet_wire Has a higher temp. http://www.mwswire.com/awgsearch2.asp Size 30 insulation PE (plain enamel) INSULATION INFORMATION: Temperature Class: 105° C Insulation Type: Plain Enamel MWS Code: PE NEMA Specification: MW 1C Federal Specification: JW1177/1 IEC Specification: NONE Insulation Characteristics: Available in 40 - 44 AWG, Plain enamel magnet wire is insulation with a film of conventional oleoresinous enamel. Enamel has good adherence, flexibility, thermal and solvent resistance. Enamel requires mechanical stripping prior to soldering. General Applications: High production relays and coils. Avoid using in presence of synthetic solvents. Looks like your mileage may vary on this one, Roy. If you decide to do this, go low on temp and slow rather than a bit higher and quicker. Wes |
#6
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Unpotting a transformer
On Mon, 20 Apr 2009 21:55:56 -0500, RoyJ
wrote: That's what I thought at first but when you pour the goop in, the temperature drops rapidly, the core never sees the high temp. When you reverse it, the leads would see the overtemp. I can get at all the leads, I could just saw the case apart and leave it potted. So what is your question, Roy? The potting material sounds like Minerallac. |
#7
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Unpotting a transformer
RoyJ fired this volley in
m: That's what I thought at first but when you pour the goop in, the temperature drops rapidly, the core never sees the high temp. When you reverse it, the leads would see the overtemp. I can get at all the leads, I could just saw the case apart and leave it potted. I worked for Transitron in their prototype testing lab, back in the '70s. Properly done: You bake the core to potting temperature to ensure a bond, and to drive out moisture. Pour in the molten Aslac. (Gilsonite and mineral oil-- we used to blend our own). You pull a vacuum with the item completely immersed in the potting compound, then release the vacuum. All the interstices are filled. Then you cool it. The core definitely sees the whole temperature -- you bring it up before adding the potting comp. Wire with a "working temperature" of 130C can easily take a passive run to 150C (with no voltage across a coil). LLoyd |
#8
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Unpotting a transformer
On Apr 21, 7:01*am, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote: I worked for Transitron in their prototype testing lab, back in the '70s. * LLoyd Did you know George Roach? |
#9
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Unpotting a transformer
Jim Wilkins fired this volley in news:7eee5e00-
: On Apr 21, 7:01*am, "Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote: I worked for Transitron in their prototype testing lab, back in the '70s. * LLoyd Did you know George Roach? Lord! That name is awfully familiar... but it's been a lot of years since then... I just don't remember. How 'bout Bob Rinderle? Clyde Duensing? LLoyd |
#10
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Unpotting a transformer
On Mon, 20 Apr 2009 17:51:02 -0500, RoyJ
wrote: I picked up a 600 watt power pack for running those little sidewalk and yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. Why do you need to de-pot the transformer? |
#11
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Unpotting a transformer
Size, heat dissipation, plus the case has two sections (the other
section is for the defunct timer and photocell circuits), I will only be using 1. OK, the real reason is that all that goop offends me!! Don Foreman wrote: On Mon, 20 Apr 2009 17:51:02 -0500, RoyJ wrote: I picked up a 600 watt power pack for running those little sidewalk and yard lights. Photo sensor is shot, transformer is massive. Salvage time. But the whole transformer is potted in some sort of black tar. I scraped some of it out, looks like it softens at 200F, goes semi liquid at 250F, and fully liquid at 275F. Easy enough to rig a tent over a catch basin and aim a heater in there but what about the temp rise on the wires? I would need to run it at the 250F to 275F (120C to 135C) range for perhaps an hour to get all the goo out. Why do you need to de-pot the transformer? |
#12
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Unpotting a transformer
On Sat, 25 Apr 2009 09:08:01 -0500, RoyJ
wrote: Size, heat dissipation, plus the case has two sections (the other section is for the defunct timer and photocell circuits), I will only be using 1. OK, the real reason is that all that goop offends me!! Ah! So you don't need or plan to separate the lams for a rewind. AxMan often has Cadmium Sulfide photosensors. So does Radio Shack. |
#13
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Unpotting a transformer
This unit has 2 circuits, an integral timer circuit, photocell, and
solid state relay programmed with a single button that is potted in the other compartment of the case. I don't really need the unit for it's original purpose, just wanted a clean 28/24 volt CT 25 amp transformer for other projects. Hampton Bay sku 591-331 vendor # RK610543 mfg 06/04 I presume it is from Home Depot. Don Foreman wrote: On Sat, 25 Apr 2009 09:08:01 -0500, RoyJ wrote: Size, heat dissipation, plus the case has two sections (the other section is for the defunct timer and photocell circuits), I will only be using 1. OK, the real reason is that all that goop offends me!! Ah! So you don't need or plan to separate the lams for a rewind. AxMan often has Cadmium Sulfide photosensors. So does Radio Shack. |
#14
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Unpotting a transformer
On Sat, 25 Apr 2009 11:52:31 -0500, Don Foreman wrote: AxMan often has Cadmium Sulfide photosensors. . What a neat place to go rooting in. My son introduced me to it when I visited him at the Univ of MN when he was there for a summer engineering program a couple of years ago. That and Cheapo, the used CD place. RWL |
#15
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Unpotting a transformer
GeoLane at PTD dot NET GeoLane at PTD dot NET writes:
On Sat, 25 Apr 2009 11:52:31 -0500, Don Foreman wrote: AxMan often has Cadmium Sulfide photosensors. . What a neat place to go rooting in. My son introduced me to it when I visited him at the Univ of MN when he was there for a summer engineering program a couple of years ago. "There's no place anything like this anywhere near here, so this MUST be the place..." It's been decades, but I recall the ?almost? free sodapop... -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
#16
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Unpotting a transformer
replying to RoyJ, justme wrote:
RoyJ, I know that it's been almost a decade since this project started, but could you please confirm if getting the black goo out makes the transformer reusable? I have one and would like to rewind it, but would like to know if it worth the trouble before breaking it apart... -- for full context, visit http://www.polytechforum.com/metalwo...er-178168-.htm |
#17
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Unpotting a transformer
On Mon, 15 May 2017 13:18:02 GMT, justme
wrote: replying to RoyJ, justme wrote: RoyJ, I know that it's been almost a decade since this project started, but could you please confirm if getting the black goo out makes the transformer reusable? I have one and would like to rewind it, but would like to know if it worth the trouble before breaking it apart... Usually, one determines the need to unpot an xfmr -because- that the xfmr tested out shorted/open. That generally means it will need to be rewound. One seldom unpots working devices. It's too much of a headache to do, especially when the component is destroyed in the attempt to get the black goo off it. Most potting compounds are serious bitches to remove, and most solvents can destroy the components before they even touch the potting compound. g Trying to unpot the bottom of a board just -to- test it can destroy the board, as well. Potted things are most often tossed. -- In today’s academia and mainstream media, we’re all guilty of hate until proven leftist. --Robert Knight, senior fellow, American Civil Rights Union |
#18
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Unpotting a transformer
On Mon, 15 May 2017 13:18:02 GMT, justme
wrote: replying to RoyJ, justme wrote: RoyJ, I know that it's been almost a decade since this project started, but could you please confirm if getting the black goo out makes the transformer reusable? I have one and would like to rewind it, but would like to know if it worth the trouble before breaking it apart... Unless the transformer is utterly positively unique and another one cannot be modified and installed..or simply new holes drilled and a new transformer installed...there is absolutely no reason to repot one. Not unless you are trying to restore a 1901 Bramford 10 three sided spoke shave with optional threading, back to exactly original condition. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#19
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Unpotting a transformer
On Mon, 15 May 2017 13:18:02 GMT, justme
wrote: replying to RoyJ, justme wrote: RoyJ, I know that it's been almost a decade since this project started, but could you please confirm if getting the black goo out makes the transformer reusable? I have one and would like to rewind it, but would like to know if it worth the trouble before breaking it apart... for full context, visit http://www.polytechforum.com/metalwo...er-178168-.htm What possess designers to use light Gray text on White background? Regards, Boris Mohar Got Knock? - see: Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca void _-void-_ in the obvious place --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#20
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Unpotting a transformer
On Tue, 16 May 2017 08:23:16 -0400, Boris Mohar
wrote: On Mon, 15 May 2017 13:18:02 GMT, justme m wrote: replying to RoyJ, justme wrote: RoyJ, I know that it's been almost a decade since this project started, but could you please confirm if getting the black goo out makes the transformer reusable? I have one and would like to rewind it, but would like to know if it worth the trouble before breaking it apart... for full context, visit http://www.polytechforum.com/metalwo...er-178168-.htm What possess designers to use light Gray text on White background? Boris Mohar Boris, every time I see a site like that, I write to their CS and tell them to buy their web designer a copy of Jakob Nielsen's wonderful book, entitled _Designing Web Usability_. If nothing else, give text some contrast from the background color, please! -- In today’s academia and mainstream media, we’re all guilty of hate until proven leftist. --Robert Knight, senior fellow, American Civil Rights Union |
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