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From: Zen Cycle <funkmaster@hotmail.com>
Newsgroups: rec.bicycles.tech
Subject: Re: RE: For those who believe in electricity
Date: Mon, 7 Apr 2025 12:17:17 -0400
Organization: A noiseless patient Spider
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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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