Power supply variation

[g1]

But you can use a center-tapped choke as a phase inverter. (a different kind of phasing issue, I know)

[trobbins]

A serendipitous option is a not too old flouro choke for 240VAC operation and common 20W tube size - it measures about 1.6-2H and is fine for up to 300mADC (5W dissipation).

[J M Fahey]

A serendipitous option is a not too old flouro choke for 240VAC operation and common 20W tube size - it measures about 1.6-2H and is fine for up to 300mADC (5W dissipation).

Cool info, being in 220V Argentina and given the worldwide conversion trend to Led lighting, I can buy old such chokes by the pound, literally.
I just pay recyclers the copper weight price , at recycling prices of course, so about half the "new copper" one.

[trobbins]

Yeh they are quite plentiful here in Oz and have quite a nice high self-resonance around 10kHz, so act like an inductor a bit better than commonly used chokes.

A slightly better fit for valve amp power supplies is the physically smaller flouro choke for 9/13W tubes, that is good for 200mA where it measures 2.7H.

[Helmholtz]

A serendipitous option is a not too old flouro choke for 240VAC operation and common 20W tube size - it measures about 1.6-2H and is fine for up to 300mADC (5W dissipation).

How did you measure inductance at 300mADC?

[trobbins]

I've been using this technique:
https://www.dalmura.com.au/static/Ch...easurement.pdf

The jig part values can be changed to vary the size of the AC applied signal if needed, although I mainly test small signal AC inductance for CLC type chokes that come across my bench. It takes a few measurements to 'plot' the Idc versus L characteristic, but circa 3-4 points identifies what is going on in the choke as the Idc level increases through the nominal application or rated level, and if 1A type AC winding(s) are used then that covers testing most chokes for valve amps. I use my old valve tester as the AC supply, as it has front panel switched heater voltages ranging up 120V.

[J M Fahey]

EXCELLENT and very well documented measurement technique.
A tribute to the memory of our lamented friend Roly Roper.

[trobbins]

Roly was very supportive to all who met him, and an inspirational figure - whether it was recycling some old PC power supply, or just going that extra mile for someone.

We had some memorable emails in the few years I knew him. He wasn't backwards in loathing certain things - 'pdf' doc's being one, but he didn't hold that against me - so I will happily share a 2009 email excerpt related to a VASE amp write-up I did for AVA - for those who knew him and can hear his voice in the following words:

"In five years of running AVA I've had *one* abusive e-mail, and that from a (editorial redaction) taking issue with my attitude to .PDF's ... an employee of Adobe no doubt. He didn't bother to address the fact that Adobe is by far the slowest app I use, and if it were not for the fact that electronic parts datasheets seem to have standardised on PDF, and site contributors use it, I simply wouldn't bother. But since I am forced to use it, I don't see why I shold be polite about it wasting my time. You should hear what I have to say about Yahoo mail!

It's ironic that he called me a "Luddite" when my objection is that .PDF is rooted in a fading past of the printed document - ink on pulverised tree. I don't have a problem with a photocopy format, just that PDF isn't *good* enough.

I'm basically "open source", and I see PDF as the child of business and government who want to control what we see and how we use it. When I find that I can look at a circuit on the screen but the tool to abstract it has been inhibited by the author/distributor I used to get mad. Now, using <printscreen>, IrfanView and Merge, I get even. :-)

But I didn't say "never", I said "normally", and your file is clearly one of those exceptions."

RIP RR

[Helmholtz]

Thanks fo sharing!

[J M Fahey]

He hit the nail right on the head, .PDF is nothing more than the "evolution" of book/magazine/newspaper *large* printing shops software specifically dedicated to run electronic versions of Linotype composer machines and their equivalent.

Revolutionary ... in the 70's when Postscript Inkjet and Laser printers allowed in house printing but as he mentions, tied for better or for worse to *fixed size* paper sheets.

Absolutely dated and quite useless in modern electronic screen devices, such as tablets, smartphones and EBooks because in general it does NOT allow for text flow and image repositioning to fill smaller than letter size screens.

You either end up with an impossible to read tiny full page or if you enlarge it, you only see part of a text line and have to jump right and left all the time.

The proper format in that case being text flow capable EPUB.

And for images, be it pictures or schematics, real graphic formats such as .gif or .jpg can be displayed straight in the page, and, more important, allow for easy editing.