Junkbox switch for a switcher

as long as everything means the transformer.

NT

He just needed a switch, hence "everything you need," but this would also get him a flyback transformer, high voltage switch, & a crappy h.v. cap.

Cheers, James Arthur

Oh, and a PWM controller, too. --ja

It gets him 200v or 400v low beta low current transistors, a reservoir cap that's too small by far, etc.

NT

China is the main and soon the only source of electronics modules. Local stocking went out even before local manufacturing, so what do you expect?

The switches are always MOSFETs these days, IME, all sized for 220VAC inputs. Haven't seen a BJT ever.

The reservoir cap's value is fine for 10mA, but ESR is poor.

Still, for $1 at the thrift store he gets a good switch, pre-fab magnetics, and a PWM chip if he wants it. That's not bad.

Cheers, James Arthur

And my junkbox switcher is already up and running! ; )

Alkaline ones produce in excess of 1A short circuit.

Another option is a stack of CR2032s in a rolled up paper, I got 10 for $2 at one discounter, sure beats that price.

I built a flyback using the small 5V standby "transformer" from a PC power-supply and some mid-sized BJT (TIP31 perhaps) as a blocking oscillator and got ballpark 200V out from 5V in.

Huh? Superglue for dissasembly - how does that work? Some sort of solvent I could understand, but glue?

The 400v cap sized for 60HZ will be way too big, almost certainly too much ESR, and the 400V rectifier may be way too slow, but UF2008 costs less than 1N4007 so you might be lucky there.

Think diagonally. ;-) You'll likely break as many cores as not, during disassembly... the final step of disassembly is partial reassembly. :^)

Super glue is just fine for redoing fractured cores. The fracture is usually simple and rough, so superglue adds little gap, and the pieces align accurately. You only need to avoid fractures on super-high mu cores (>5000?), where even that little gap will spoil the inductivity a bit.

Tim

I've never seen a PWM chip in a cheapo wallwart. Ever.

NT