LEDs - getting there slowly.

I have given up buying LED's on ebay. What the specification says and what they produce seem to be completely different things.

I'm surprised that SMD LEDs can achieve >100lm/W. Typically, I only see that with COB or LED filament bulbs.

If they're such high achievers, why do they fail to get the A++ rating?

NT

Not sure I'd believe the claims of a no-name brand on eBay to be be at the forefront of luminous efficiency ...

John Lewis.

I recently bought a bar with four LED lampholders from John Lewis. Iy came with four bulbs rated at 330 lumens. The output was useless. I replaced them with four 450 lumen jobs from eBay. Perfect.

I subsequently bought a further 20 from the same source and fitted five in my kitchen. After two days one ceased working. The supplier did not quibble and gave me a refund almost by return. I would buy from them again.

You just have to be lucky when buying on the Internet generally.

Well yes - and in that envelope, with its usual orientation, the potential for overheating is obvious. I generally look for COB ('filament' is COB), but I have other SMD LEDs (the (now getting old) 5050 chip is pretty good) partly for dissipation of heat local to the chip and partly for omnidirectional light.

Too true! These do seem to be good thought - I put one in an adapter (BC-->GU10) in a batten holder in the kitchen and, on its own, it was good on the work tops over most of the kitchen. Of course, the biggest drawback with any downlight is lack of overall light reflected from the ceiling.

Ah yes. Bit like the 1960s Sinclair Radionics kits and transistors then.

I have never seen a Hifi Amplifier since my friend bought the Sinclair Z12 as a kit, where you could actually SEE the crossover distortion on an oscilloscope.

Thanks. I was looking at that one last week so thanks for the heads-up.

Is there a big difference between 330 and 450? By my mental arithmetic that must be aboult half a stop in photographic terms.

depends how you calculate it and where you draw the arbitury bands a bit like council tax bands.

IIRC there was a Sinclair audio amp kit where the (output) transistors got killed if the speakers were disconnected whilst the amp was powered up!

Unless it's a long standing brand name in th elighting business (Philips / Osram etc) supplied through reputable wholesalers / retailers their claims on lumens and colour temperature and CRI will always be total bollocks just like the amp hour ratings of rechargeables and USB powerbanks

In which case they're free. I get all my batteries for free from China. I buy the battery, test it, find it's about a fifth of what it claims to have as a capacity, then complain. Money back straight away. They'll learn one day.

I've given up with LED bulbs, they overheat and die in a few months. Get LED striplights, at least they can stay cool enough not to kill the LEDs. Anything too hot to touch is going to die very quickly.

I used a Z12 in late '69 as an additional amp to the record player we were using. Talk about inadequate heat sinks! After a few minutes they were distorting like hell as they overheated.

Any idea what the TO3 "reject" output transistors were? OC28? OC35?

The LED reading lamps I bought which are supposedly "warm white" are whiter than a Glaswegian's belly.

I only buy from LEDHut these days.

By definition they werent either, as they would have failed to meet the specs for either.

OC28-36 appear to have been selections from the same chips.

Clive would have acquired what failed to reach even an OC30 spec.

My impression at the time was that the gain was about 5 on one and 10 on the other.

I buy the battery, test it, find it's about a fifth of what it claims to h ave as a capacity, then complain. Money back straight away. They'll learn one day.

Some of us have better things to do than buy crap batteries from china, tes t them, then send them back, there is much more to life out there in the re al world, although probbaly not much up north given the current weather so knock yourself out testing batteries or use your usual method of head butti ng the door frame ;-)