12V Electronic Tranny

I don't see that the transformer is in danger of overheating as long as the frequency remains essentially the same as with 60W load and the winding gauge is conservatively rated- doubling the current does increase the heat production by a factor 4x. I would be concerned about an SOA or peak power abuse of the transistors though.

Nah- I don't even think that's likely with your big step-down ratio.

** Check the two data sheets I supplied.

My nominal "60VA", Aussie built replacement has more rugged transistors than the "100VA" Taiwanese built original.

BTW 1.

The Taiwanese one had no current limiting cct.

BTW 2.

The cause of the failure of the original is almost certainly that it was run from a leading edge (ie triac) dimmer.

....... Phil

How would Phil Allison know that something was right? And would anybody be interested in his opinion? He does seem to be pig-ignorant about transformers, which is odd in valve freak from the hi-fi lunatic fringe.

--
Bill Sloman, Nijmegen

Right- those transistors are rugged, I don't see a problem with 150W.

Right- my observation is that all Asia knows how to do is produce cheap trash that *looks* like the real thing, and this is not only electronics. A domestic manufacturer would be fined or sued if they produced garbage like that.

That would definitely do it. You can dim the circuit but it has to be internally through that R-C circuit to the DIAC.

"Fred Bloggs"

** There is however a * very persistent rumour* - Fred - that if one uses a "trailing edge" dimmer - ie IGBT or GTO Triac based, then these primitive little suckers survive for yonks, just fine.

........ Phil

I can believe that- anything that avoids some big instantaneous voltage spike being applied to the whole circuit. How readily available are these trailing edge dimmers?

"Fred Bloggs"

** Well, the Chinese are onto them....

........... Phil

how do you tell? (3C85 stamped on the side would be one way)

if the switching frequency isnt astonishingly low, then thats a fairly good way of telling its not iron powder (although #2 has pretty low losses).

OK, you got me there ?!

Cheers Terry

Lutron calls it TE dimming. It's also called "Reverse Phase Control" in the industry. That search term brings up all kinds of cool stuff, like Atmel's U2102B phase-controller IC,

With respect to the issue of "Silent Dimming," reverse phase control is said to be just as bad as ordinary phase control, and not a replacement for true sine-wave dimmers.

--
 Thanks,
    - Win

"Winfield Hill"

** Trolling and context shifting - as usual.....

** TE = Trailing Edge - no ??????

** The Septics just *have* to use their own names - just so they can pretend to have invented whatever it is. ** Said just like a fish looking to buy a bicycle.

........ Phil

that makes sense. really, if the phase angle is set to 90 degrees, neither I nor Fourier can see a difference between leading- and trailing-modulation in terms of harmonics. extends to any phase angle of course.

BUT I can see a difference in terms of lightbulb life - leading edge modulation gives a whacking great thump to a cold lamp, trailing-edge is much nicer. Given that lamps inevitably fail at turn-on, this is well worth doing.

BTW Phil, exactly how do you tell its ferrite not iron powder? has it got a ferrite code written on it? is it an ETD core (AIUI there are no Iron Powder ETD cores, but they come in all the E core sizes)?

Cheers Terry

"Terry Given"

** Complete nonsense.

Phase control dimmers are faded up from zero - unlike a switch.

** It only matters with electronic transformers.

** In popular mythology only.

........ Phil

[something that Phil Asshole snipped]

Perhaps, but the first thing I noticed is that in the original Latin, it was "quod". I don't think there's a word "quad" in Latin.

Cheers! Rich

see, I knew I'd make a typo

Are you the same Winfield Hill that co-authored 'Art of Electronics' with Paul Horowitz?

If so--a few questions:

1) Any plans for a 3rd revision? I just finished reading this book and I loved it--although quite obvious that it need a lot of updates

2) Anywhere that I can find answered/worked exercise solutions? Particularly on the 'bad circuit' ideas? This was the biggest shortcoming of the book in my opinion. Also, there were a lot of 'this is obviously x volts' throughout the text, where things were assumed 'obvious' that were not. I am using this text to help 'refresh' me for my PE exam in April.

Many thanks,

Paul

?that co-authored 'Art of Electronics' with Paul Horowitz?

. .