Well I never! Light sensitive record deck.

[vinrads]

I have a Sony record deck on the bench , after freeing off the mech , it would sometimes drop in the L/P position when plying 7" after much scratching of head , I stumbled across the culprit it was an LED lamp above the bench , I know it detects the size of the record by covering the slots on the mat . Mick.

[Nickthedentist]

Well found.

Very well known problem when servicing video machines, but useful reminder that other things can be affected too.

[vinrads]

The confusing thing is it's ok with the normal incandescent lamps . Mick.

[vidjoman]

LED lamps tend to flash, as do many fluorescent lamps whereas tungsten lamps give a more even light. Our eyes seem to be able to not see the flashing, just as we don’t see the flashing picture on a tv because the rate is too fast.

[Sideband]

How many times did we encounter a similar problem in the early days of video recorders? As pointed out though, other things can be affected and it's worth bearing in mind if you get odd things happening.

[Radio Wrangler]

Originally Posted by vidjoman

LED lamps tend to flash, as do many fluorescent lamps whereas tungsten lamps give a more even light. Our eyes seem to be able to not see the flashing, just as we don’t see the flashing picture on a tv because the rate is too fast.

'Persistence of vision' - also available as a painting from Salvador Dali.

It's a fast-attack, slow decay phenomenon. HP's first calculators used LEDs, strobed to keep down the number of connections to the little 3 and 5 digit packages. But the strobing had a second effect, the same average power looks brighter when pulsed, than if done as a continuous level, so the battery charge lasted longer.

The asymmetric rise and fall times of the eye acted to shift the apparent mean level.

David

[Richardgr]

There is a turntable that reads the LP information using light ...
Laser turntable

I found that description of a product, but I had thought there was an older one from the 70's too?