Author Topic: How to light a preheat button start desk lamp without preheating ....  (Read 1953 times)
Powell
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How to light a preheat button start desk lamp without preheating .... « on: January 05, 2012, 03:34:28 PM » Author: Powell
I have a 14 watt desk lamp in the kitchen. Normally you have to press the button for about 2 seconds to light it.  This morning I walked over and just touched it with my arm and it came on. I had built up a static charge, and it instant started.

Tingle!  


Powell  :a_fluor:  NO :a_starter:
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Medved
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #1 on: January 05, 2012, 04:57:24 PM » Author: Medved
The F15T8, F8T5 and shorter lamps in 230V circuits with nearby grounded reflector tend to instant-start without the starter and they do not even need the "charged touch"...
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Ash
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #2 on: January 05, 2012, 05:21:12 PM » Author: Ash
40W T12 in series with inductor ballast and without the starter, in warm ambient, will instant start and go lighting dimly. Tungsrams often would even instant start into full brightness. I wonder why the way shorter lamps in the desk lamps you have dont do this
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Medved
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #3 on: January 06, 2012, 01:07:30 AM » Author: Medved
The dim glow discharge is present in many lamps, include many F18T8, in warmer days it sometimes start even in F36T8, but that I do not count as the start - as the discharge does not move towards the "full fat" arc.
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Ash
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #4 on: January 06, 2012, 12:41:45 PM » Author: Ash
In the desk lamps with manual start, the off switch is NC in series with the lamp. so after you release it, the lamp can get to this partial disharge again

How the desk lamps stay off after releasing the off switch without starting back to this state ?

And i never seen this happen in 18W / 36W T8. It does happen with T12s and in Tungsram 20W and 40W it sometimes does turn into full discharge on its own
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Medved
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #5 on: January 06, 2012, 04:09:57 PM » Author: Medved
How the desk lamps stay off after releasing the off switch without starting back to this state ?

Manual start desk lamps I have seen (mainly here, most F15T8/12) either run on 120V, or use two lamps in series.
So it mean ~120V/lamp, what is not enough to coldstart the discharge.

And i never seen this happen in 18W / 36W T8. It does happen with T12s and in Tungsram 20W and 40W it sometimes does turn into full discharge on its own

I've seen this in fixtures, where the starter connection contacts failed, the glow was only very tiny (visible practically in darkness only).
But two series F15T8 on an incandescent 230V/60W lamp ballast tend to start quite reliably when approaching charged with the static electricity, but the grounded reflector is not enough...
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Powell
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #6 on: February 01, 2012, 04:29:46 PM » Author: Powell
I remember many MANY  decades ago what happened when my neighbor's house got struck by lightning. I had just gotten in bed and turned OFF my F15T8 manual start desk lamp and gotten in bed after a bathroom run. My eyes closed, there was this BRIGHT light at the same time SSSHHHTT and BOOOOOOOM!  I got up and the lamp had turned back on and I thought our house had been struck by lightning. (It's 2 AM) It's storming and pouring rain, and I, in pajamas climbed up on the metal roof ( ladder was on the upstairs porch) and quickly inspected to make sure house was NOT on fire. I was soaked. I found out later it wiped out the front end FET in my Advent table radio which had only "rabbit ears" antenna. The Collins 75A1 receiver, on and still connected to the 80 meter ham antenna had no damage.  Tube type radios are so much better built....   ;D


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SOX55W
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120V 60Hz here!


Re: How to light a preheat button start desk lamp without preheating .... « Reply #7 on: February 01, 2012, 07:06:54 PM » Author: SOX55W
@Powell The old stuff was definitely well built, but FET transistors are very sensitive to static discharge.  You could probably microwave a tube for 10 seconds and it would still work fine.  ;D  I remember my dad was into ham radio when I was growing up. He had a ~60ft long antenna out in the back yard and we always disconnected it from the equipment every time a storm approached.
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Re: How to light a preheat button start desk lamp without preheating .... « Reply #8 on: February 01, 2012, 09:14:22 PM » Author: Powell
I had forgotten to disconnect the antenna from the antenna switch AND turn the radio off.  I am surpized the lightning didn't hit the antenna.

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