Do xformers w/ built-in capacitor exist? - Electronic Circuits Projects Diagrams Free

HiTech · 4th January 2007, 01:19 PM

Ok here's another off-the-wall question for y'all. Last night I'm disassembling a high voltage supply for parts salvage. After assuring that the filter cap is indeed discharged, it gets removed along with the rectifier, etc. Now to remove the xformer itself. As I remove the mounting hardware, the screwdriver blade slips, contacts one secondary leg of the xformer and SNAP! a spark occurs!! Looking closely at the xformer, all I can see are the usual windings with no indicators that there is an intyernal capacitor. Anyone aware of xformers being built with an onboard cap that's not obviously visible to the technician? The service schematic shows only the standard symbol for the xformer, nothing else special that would indicate a potential internal capacitor. Hmmmm.

HarveyH42 · 4th January 2007, 05:00 PM

Do you know how a capacitor is built? See any similarities? Wouldn't think it very efficient or hold a charge for long.

Optikon · 4th January 2007, 05:19 PM

Quote:

Originally Posted by HiTech

Ok here's another off-the-wall question for y'all. Last night I'm disassembling a high voltage supply for parts salvage. After assuring that the filter cap is indeed discharged, it gets removed along with the rectifier, etc. Now to remove the xformer itself. As I remove the mounting hardware, the screwdriver blade slips, contacts one secondary leg of the xformer and SNAP! a spark occurs!! Looking closely at the xformer, all I can see are the usual windings with no indicators that there is an intyernal capacitor. Anyone aware of xformers being built with an onboard cap that's not obviously visible to the technician? The service schematic shows only the standard symbol for the xformer, nothing else special that would indicate a potential internal capacitor. Hmmmm.

I dont know of any with it built in... that would be a custome job for sure.. so it is doubtful. However, obviously, there was stored charge somewhere. To play it safe, I would take an earth grounded wire and probe "everything" in there first to discharge all circuits that are unknown.

**Nigel Goodwin** · 4th January 2007, 05:58 PM

Assuming it's something like a TV LOPTX?, they often use the capacitance between the windings along with internal rectifiers (it's called diode-split).

Hero999 · 4th January 2007, 06:26 PM

I've seen TV flyback transformers with built in multipliers; is this is what you're talking about Nigel?

**Nigel Goodwin** · 4th January 2007, 06:33 PM

Quote:

Originally Posted by Hero999

I've seen TV flyback transformers with built in multipliers; is this is what you're talking about Nigel?

Yes, the output winding is split (hence the name) into a number of seperate windings, all placed in series with rectifiers in between - the capacitance between the different sections means you don't need any extra ones. Apparently the most common fault in EHT triplers was the capacitors breaking down - this removes them.

HiTech · 4th January 2007, 07:16 PM

this was no FBT. It's a laminated steel core with a primary of 120vac, secondaries of 4v and a high voltage tap.... very much like a MOT. Oddly enough there was a label inside stating to discharge filter capacitors before servicing.... not the transformer! I even got to wondering if somehow my own body had stored a static charge and just happened to discharge it to the chassis during disassembly. However I doubt that since this was a pretty good snap!

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4th January 2007, 01:19 PM	(permalink)
HiTech	Do xformers w/ built-in capacitor exist? Ok here's another off-the-wall question for y'all. Last night I'm disassembling a high voltage supply for parts salvage. After assuring that the filter cap is indeed discharged, it gets removed along with the rectifier, etc. Now to remove the xformer itself. As I remove the mounting hardware, the screwdriver blade slips, contacts one secondary leg of the xformer and SNAP! a spark occurs!! Looking closely at the xformer, all I can see are the usual windings with no indicators that there is an intyernal capacitor. Anyone aware of xformers being built with an onboard cap that's not obviously visible to the technician? The service schematic shows only the standard symbol for the xformer, nothing else special that would indicate a potential internal capacitor. Hmmmm. __________________ Don't make me reach through this monitor to slap you a good one!

4th January 2007, 05:00 PM	(permalink)
HarveyH42	Do you know how a capacitor is built? See any similarities? Wouldn't think it very efficient or hold a charge for long.

4th January 2007, 05:58 PM	(permalink)
Nigel Goodwin	Assuming it's something like a TV LOPTX?, they often use the capacitance between the windings along with internal rectifiers (it's called diode-split). __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

4th January 2007, 06:26 PM	(permalink)
Hero999	I've seen TV flyback transformers with built in multipliers; is this is what you're talking about Nigel? __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

4th January 2007, 07:16 PM	(permalink)
HiTech	this was no FBT. It's a laminated steel core with a primary of 120vac, secondaries of 4v and a high voltage tap.... very much like a MOT. Oddly enough there was a label inside stating to discharge filter capacitors before servicing.... not the transformer! I even got to wondering if somehow my own body had stored a static charge and just happened to discharge it to the chassis during disassembly. However I doubt that since this was a pretty good snap! __________________ Don't make me reach through this monitor to slap you a good one!