Winter project.

[ppppenguin]

I've seen a dual standard 702 demonstrated on 240 lines on a couple of occasions, including at Harpenden some years ago. yes, the flicker was visible and I wouldn't like to watch it for too long but it wasn't truly appalling. TBH, I find ordinary 50Hz interlaced pictures a bit flickery. I think it's years of being accustomed to flicker free LCDs. I have one friend who was badly troubled by flicker in the days of CRT computer monitors. Even 75Hz caused her some discomfort.

[Murphyv310]

Hi.
My oldest daughter used to suffer with bad migraines. In one of her
Previous homes it had fluorescent lights in the kitchen, just about every time they were on she had a migraine. Same thing when she was at work using a CRT monitor. Now she rarely has them with LCD monitors and better lighting at home.

[ppppenguin]

Although they are still sold I don't know why you would install conventional fluorescents now. They're still cheaper than LED tubes but that's the only reason I can think of. In a commercial environment the economics of LEDs win every time, both the savings on the power bill and the cost of relamping. And the LEDs don't flicker.

Who remembers the 100Hz CRT sets made by Philips and others? Wonderfully restful looking pictures but the electronics to upconvert without bad artifacts were a problem back then. If we could have done that at the dawn of TV who would have bothered with interlace. After all, the film industry showed the way by doing "up conversion" in the projector with a mutlblade shutter.

[Murphyv310]

Totally agree Jeffrey.
My son who is closing his shop down this Friday replaced his fluorescent lights with LED a couple of years ago and made big savings on electricity costs and heat in the summer and to be fair they don't run dreadfully hot anyway.
Sad he's shutting down but Tesco only a quarter of a mile away has killed his business.

[Mark Hennessy]

A lot of LED lamps flicker at 100Hz. If they don't, they have switched-mode converters that output RFI. The trouble is, there's no way of telling which is which when buying them.

Anything less than 85Hz on a CRT is a problem for me. My old Win98 PC that still uses a CRT lets you adjust the frame rate in 1Hz steps. It's quite binary in my case: 84Hz is flickery, 85 is not. It varies enormously between individuals, but I cured lots of migraines when I first started this job back in the mid '90s by switching PCs from 60 to 85Hz. People swore they couldn't see any difference, but certainly appreciated the change.

[Murphyv310]

Absolutely.
Just think how many people would have had migraine headaches with Bairds 25Hz flicker. It does make you wonder.

[Murphyv310]

I've a few of the bridge rectifier and capacitor dropper types, some of the better ones have a 330uf 6v smoother and the 100Hz flicker is minimal. Had a couple now with blown cap droppers, takes out the fusible resistor, been able to fix them all so far.

[Mark Hennessy]

The ones Big Clive takes apart usually have 4u7 or thereabouts. Not really sure why they bothered, frankly.

The worst ones I've experienced are those trendy filament types. I don't mind the orange/yellow colour so much, but the flicker is terrible. I had a meal in a restaurant that was lit exclusively with these, and I couldn't wait to leave. Just awful...

I've repurposed some LED strips from an old 600mm square ceiling fitting. They're not the most efficient or nicest colour, but that doesn't matter for this application. I'm just in the process of building a linear PSU for them - about 42V at 300mA - with a brightness control on the current source. For lining up radios, they provide flicker-free, RFI-free light, and minimal wasted heat (which is useful anyway in a cellar workshop). I think the PSU will waste less than 3 or 4 watts all told, which is hardly worse than the original switching supply that failed. And I'm setting it up now to make it easy to modify in the future should I buy some different LEDs - just a transformer swap should get me to 12V at 1 amp, for example. I might even write it up, although I don't think it's all that interesting really...

[Terry]

I recall coming home in 1962 after a fortnight away during which I'd seen no TV at all. The first thing I noticed on entering the living room was the flicker from the TV!

It didn't take long for my vision to return to 'normal' but, after reading this thread, it has occurred to me that I've never noticed any flicker on my visits to the museum, despite rarely seeing television in any form these days.

Has anybody else noted an increased tolerance to 50Hz flicker with increasing age or am I in a minority?

[Murphyv310]

I agree with you Terry.
I'm definitely much more tolerant to flicker. Not the awful 25 Hz on 180 & 240 lines though.