Re: RE: For those who believe in electricity

On 4/7/2025 12:10 PM, cyclintom wrote:

On Sun Apr 6 22:22:33 2025 Frank Krygowski  wrote:

I'm not an electronics guy. But speaking of problems, I think I
mentioned a few days ago that on a recent night ride, my headlight (B&M
Eyc N plus),  powered by my good old sidewall generator, was randomly
and sporadically blinking off. I put the bike on the workstand, checked
out the wiring (it?s original and pristine), and spent some time
spinning the front wheel. Sometimes the headlight worked, sometimes not,
and it changed state at random without having been touched. I was
suspicious of the tiny on/off switch hidden behind a rubber plug, in
part because I felt no satisfying click.
>
I substituted a different (lower quality) LED dynamo light, which seemed
to work perfectly and probably absolved the generator. I eventually
talked by phone to Peter White, who sold me the light far longer ago
than I remembered - ten years! I asked if he had clues on diagnosing the
problem. He did not, but suggested that the identical light without the
possible failure point of an  on/off switch is just $35. (A sidewall
dyno doesn't need a switch.) Still, I opted to open the light to see if
I could spot anything because I have a compulsion about fixing things -
but a headlight has to be really, really reliable.
>
Here are photos of the electronic guts, with a vernier caliper for size
(and to educate Tom!).
>
Bottom view. The downward facing LED is at the top of the photo, the
suspicious switch is the tiny white box at the photo?s bottom.
https://www.flickr.com/photos/16972296@N08/54435279894/in/dateposted-public/
>
Top of the circuit board. The large copper pad is part of the heat sink
system, contacting a metal casting that forms the top of the headlamp
body. I?ll probably add some heat conducting goop when I reassemble:
https://www.flickr.com/photos/16972296@N08/54435279589/in/dateposted-public/
>
Although a bike generator or dynamo puts out AC, I had hoped to diagnose
it using DC, figuring a 6 volt battery would essentially supply half of
the sine wave so half of the input circuit. That naturally works with
incandescents, and it worked with one Avenir LED dyno headlight that I
repaired. Not so in this case. So I ran another generator using a roller
chucked in my drill press, attached a digital voltmeter in parallel, and
poked around best I could. I saw nothing loose, no scorched components,
nothing obviously wrong.
>
With no power attached, I tried checking for continuity across the
switch. It always showed close to zero ohms, never infinity - but the
resistance readings with pinpoint probes were jumpy, and since the
switch wasn?t isolated from the circuit, that may not mean much.
>
I used contact cleaner to blast out the switch and repeatedly clicked
it, including while power was applied. Except for a few occasions, the
light did not respond to the switch, so I still suspect the switch. When
the light was off, I had about 12 VDC. When on, about 4 VDC.
>
It?s still not fixed, but it's getting late here. I would try to simply
short out the switch, but it?s very difficult to identify and reach its
microscopic solder pads and I?m no good at micro soldering.  I think my
best bet will be to mechanically remove the switch, crushing and cutting
it as necessary, hoping that it will yield access to solder points that
I can bridge with a short. If that cures it, fine. And I?ll probably buy
that other light anyway.
>
BTW, Peter White is not pleased about the tariff situation. He says he
won?t raise prices on current stock, but with the next shipment he?ll
probably have to.

    What is the purpose of holding that PC board in a caliper?

He stated it in his message.

 Was the size of the board in question?

Wow...You don't know how to read a caliper?

Tell us the function of the PC board

He did

and the likely source of your blinking problem?

He speculated, not being an EE or Elec Tech.

Frank, you were an instructor, you do not have any practical knowledge of anything.

did you actually bother to read any of this before posting?
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