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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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Generic name for USA style of mains transformer?
Well I only see it in USA kit. A toroid but flattened into an elipse shape
in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? |
#2
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Generic name for USA style of mains transformer?
On Dec 19, 6:04*am, "N_Cook" wrote:
Well I only see it in USA kit. A toroid but flattened into an elipse shape in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? Not sure if you are referring to a 'flat pack' or a 'C' core transformer. The Flat pack has squared 'U' shaped laminations, so if you look at the core the lams are stacked [like in the common 'EI' tranformer with the coil on the centre leg], but the two coils are on the legs of the'U'. The C core is more like what you describe with the core curved around at each end and is made by winding the lamination strip around a rectangular form, then compressing it on each long side to bond the lam together, then cutting it in half midway along the 'long' side and polishing the cut ends. Two coils are wound in the conventional manner then the core halves slipped in and clamped [we used to use steel band wrapped around the perifery of the core]. The ends could be epoxied together, but that introduced a tiny air gap that affects the core performance. This core design came, originally, from Germany IIRC. I believe that the ones we were using back in the '60s came from Vacuum- Schmeltz [sp?] Neil S. |
#3
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Generic name for USA style of mains transformer?
nesesu wrote in message
... On Dec 19, 6:04 am, "N_Cook" wrote: Well I only see it in USA kit. A toroid but flattened into an elipse shape in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? Not sure if you are referring to a 'flat pack' or a 'C' core transformer. The Flat pack has squared 'U' shaped laminations, so if you look at the core the lams are stacked [like in the common 'EI' tranformer with the coil on the centre leg], but the two coils are on the legs of the'U'. The C core is more like what you describe with the core curved around at each end and is made by winding the lamination strip around a rectangular form, then compressing it on each long side to bond the lam together, then cutting it in half midway along the 'long' side and polishing the cut ends. Two coils are wound in the conventional manner then the core halves slipped in and clamped [we used to use steel band wrapped around the perifery of the core]. The ends could be epoxied together, but that introduced a tiny air gap that affects the core performance. This core design came, originally, from Germany IIRC. I believe that the ones we were using back in the '60s came from Vacuum- Schmeltz [sp?] Neil S. "image" searching on "C core " "mains transformer" didn't show any like the one in front of me http://www.jacmusic.com/lundahl/images/tube_trafo.jpg is similar but this one has a core more circular in cross-section , or maybe circular , under an all over moulded epoxy-like coating . I will take a pic tomorrow I can't see how the core could be moulded over the joins and then couils placed over, no other bracing strips around the core . |
#4
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Generic name for USA style of mains transformer?
N_Cook wrote: Well I only see it in USA kit. A toroid but flattened into an elipse shape in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? **Sounds like an 'R' core tranny to me. Excellent isolation, but higher loss than a toroidal. -- Trevor Wilson www.rageaudio.com.au |
#5
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Generic name for USA style of mains transformer?
N_Cook wrote:
Well I only see it in USA kit. A toroid but flattened into an elipse shape in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? **Like these? http://www.custommag.com/products/r-core.shtml -- Trevor Wilson www.rageaudio.com.au |
#6
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Generic name for USA style of mains transformer?
Trevor Wilson wrote in message
... N_Cook wrote: Well I only see it in USA kit. A toroid but flattened into an elipse shape in plan view and a coil around each straight section. The curved ends of the ring are exposed. Laminated core construction so easy coil winding ? **Like these? http://www.custommag.com/products/r-core.shtml -- Trevor Wilson www.rageaudio.com.au Yes it would seem R-Core, eg http://www.dibao-transformer.com/Ima...ansformer-30VA. png I wonder how they are made. Coils formed and laid over the bare cores which are then joined somehow farely seemlessly and then perhaps 4 sections of quartered pre-moulded epoxy covers slid over the cores and under the coils and plastic welded into place |
#7
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Generic name for USA style of mains transformer?
"N_Kook" Yes it would seem R-Core, eg http://www.dibao-transformer.com/Ima...ormer-30VA.png I wonder how they are made. ** An R-core is wound with one continuous strip of steel - tapering at each end to get a round cross section. The two plastic bobbins are made as halves and glue together around each straight limb of the core. There are also gear like teeth on the ends of the bobbins - allowing a machine to spin them on the core while an operator feeds them with wire. Then the bobbins and wire ends are secured and an overall insulation wrap applied. A steel claming frame is finally attached to allow chassis mounting. Clever - huh ? ..... Phil |
#8
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Generic name for USA style of mains transformer?
Phil Allison wrote in message
... "N_Kook" Yes it would seem R-Core, eg http://www.dibao-transformer.com/Ima...ansformer-30VA. png I wonder how they are made. ** An R-core is wound with one continuous strip of steel - tapering at each end to get a round cross section. The two plastic bobbins are made as halves and glue together around each straight limb of the core. There are also gear like teeth on the ends of the bobbins - allowing a machine to spin them on the core while an operator feeds them with wire. Then the bobbins and wire ends are secured and an overall insulation wrap applied. A steel claming frame is finally attached to allow chassis mounting. Clever - huh ? .... Phil Ah! its now so obvious, had me scratching my head. I never thought of winding the bobbins while on the core, yes clever. I'd worked out how fully enclosed toroidal transformers with solid cores were wound, a few months back, even made a sort of m/c for doing it, but this type had me flumoxed On a side matter relating perhaps to their efficiency. The one in front of me gives off various voltages and the associated DCs are marked on the overlay (no schematic available). All the DC voltages , amplifier but just quiescent no load, all the actual DC levels are about 10 percent less than the overlay marked DC. If one of these C or R type cores is knocked/ abused / thermal stress/vibration and the closure face opens up muicroscopically, could that cause a 10 percent drop in secondary voltages? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#9
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Generic name for USA style of mains transformer?
"N_Kook" Phil Allison http://www.dibao-transformer.com/Ima...ansformer-30VA. png I wonder how they are made. ** An R-core is wound with one continuous strip of steel - tapering at each end to get a round cross section. The two plastic bobbins are made as halves and glue together around each straight limb of the core. There are also gear like teeth on the ends of the bobbins - allowing a machine to spin them on the core while an operator feeds them with wire. Then the bobbins and wire ends are secured and an overall insulation wrap applied. A steel clamping frame is finally attached to allow chassis mounting. Clever - huh ? Ah! its now so obvious, had me scratching my head. I never thought of winding the bobbins while on the core, yes clever. I'd worked out how fully enclosed toroidal transformers with solid cores were wound, a few months back, even made a sort of m/c for doing it, but this type had me flumoxed On a side matter relating perhaps to their efficiency. The one in front of me gives off various voltages and the associated DCs are marked on the overlay (no schematic available). All the DC voltages , amplifier but just quiescent no load, all the actual DC levels are about 10 percent less than the overlay marked DC. If one of these C or R type cores is knocked/ abused / thermal stress/vibration and the closure face opens up muicroscopically, could that cause a 10 percent drop in secondary voltages? ** Nope. Look elsewhere for the explanation. ..... Phil |
#10
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Generic name for USA style of mains transformer?
Phil Allison wrote in message
... "N_Kook" Phil Allison http://www.dibao-transformer.com/Ima...ansformer-30VA. png I wonder how they are made. ** An R-core is wound with one continuous strip of steel - tapering at each end to get a round cross section. The two plastic bobbins are made as halves and glue together around each straight limb of the core. There are also gear like teeth on the ends of the bobbins - allowing a machine to spin them on the core while an operator feeds them with wire. Then the bobbins and wire ends are secured and an overall insulation wrap applied. A steel clamping frame is finally attached to allow chassis mounting. Clever - huh ? Ah! its now so obvious, had me scratching my head. I never thought of winding the bobbins while on the core, yes clever. I'd worked out how fully enclosed toroidal transformers with solid cores were wound, a few months back, even made a sort of m/c for doing it, but this type had me flumoxed On a side matter relating perhaps to their efficiency. The one in front of me gives off various voltages and the associated DCs are marked on the overlay (no schematic available). All the DC voltages , amplifier but just quiescent no load, all the actual DC levels are about 10 percent less than the overlay marked DC. If one of these C or R type cores is knocked/ abused / thermal stress/vibration and the closure face opens up muicroscopically, could that cause a 10 percent drop in secondary voltages? ** Nope. Look elsewhere for the explanation. .... Phil Increase of DC saturation characteristic of iron powder over time? If so that would apply to toroidal transformers also and I've never noticed a 10 percent drop in a toroidal |
#11
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Generic name for USA style of mains transformer?
"N_Kook"
Look elsewhere for the explanation !!!!!!!!!!!!! Increase of DC saturation characteristic of iron powder over time? ** What " iron powder " ? Wot an annoying bloody imbecile. ..... Phil |
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