ZL H501R switch replacement

Hi all,

I have a H501R (red emitter) which worked fine so far.
Suddenly it stopped working : did not light up at all. It has not fallen down, no shock, no water, nothing special.
So I cleaned the contacts, and put it a fully charged NiMH : worked again sometimes, but with an erratic behaviour.
Tried a fresh primary Alkaline : again erratic behaviour. Same with a fresh primary Lithium.
What I call "erratic behaviour" is:

• Sometimes after the battery change I see the very short and bright usual flash when tightening the tailcap, and then it works normally.
• On other battery changes the LED will turn on permanently but very faint. Any action on the switch (either short or long click) does not turn out the LED, I need to unscrew the tailcap to make it go off.
• Sometimes on battery change the LED glows dim for a fraction of a second, then turns off. One click will turn it on again for a few seconds (very dim) then out.
• Sometimes it will not turn on at all, I don't even see the initial brief flash.

I then tore the switch boot off, and sprayed the switch contacts with contact cleaner. It seemed to solve the issue, but this worked only temporarily: now it doesn't light up any more. So I'm afraid I have to replace the switch with a new one, hence the following questions:

• Do you confirm I have to de-solder the four legs of the switch (see picture below)?
• Where can I find such a switch (it is 5.8 x 6.3mm)? I assume AE and other Chinese vendors sell such switches, but how to find the correct one?

Thanks in advance for your help.

I agree it sounds likely the switch is bad. Your list of symptoms isn't conclusive, but changing the switch is neither hard nor expensive.

Based on the looks, I'd guess that's a momentary switch. The other type of switch often used in flashlights is a 'clicky', either forward or reverse type. These are larger (AFAIK) than what is in your picture. These click once for on and again for off, like a ball-point pen. The momentary switch is on when you press, and off when you release. If you have a driver with a microprocessor in it, it is easy and cheaper to use a momentary switch to control modes, etc. For lights with no modes or intelligence (like old style MAG lights), a clicky is easier and cheaper to use.

Yours looks like what is known as a 'tactile' or 'tact' switch because they usually have a very distinct tactile 'click' when you activate them. They are very common, and very inexpensive. You could certainly find one on the cheap discount sites, but you'd have a better time finding specs (like dimensions) for them if you went to an electronic component distributor. If you were in the US, I'd recommend DigiKey or Mouser, but you must have them or the equivalent in France, maybe RS or Farnell? Two things you are looking for are to match the mechanical dimensions so it will fit in your light, and make sure the circuit is correct.

I think the more common circuit configuration is that the lower two legs are tied together, the upper two are tied together, and the switch is between the upper and lower. The other possibility is that the left two are tied together, the right two are tied together, and the switch is between left and right. Obviously there are other possible configurations, but I don't think anyone makes anything but these two. I usually design boards so two diagonal legs are used. This way it doesn't matter what the circuit configuration of the switch is. When you get the switch off, you will be able to see which configuration your board is designed for.

You are right that you have to unsolder the four legs. The safest way to do this, especially if you are not an expert, is to cut the legs first, remove the part, then unsolder the remaining bits one at a time. It is possible to unsolder the part without damaging it, but there's much more risk of damaging the board. At solder melting temperature, the epoxy holding the board together loses most of its strength. So it's important to minimize mechanical stress on the board when you are soldering or de-soldering. The board is MUCH stronger at room temperature.

Many thanks DIWdiver alias "switch expert" :twothumbs for such a detailed reply.
Yes my switch is most likely the momentary tactile type: the Zebralight UI is "short click = ON or OFF", "long click = LOW then MID-HIGH".
OK, I'll remove the switch following your advice and let you know the result.

Second opinion…

Send it to ZL for a proper repair.

AstroTurf said:

Send it to ZL

Click to expand...

This was my first try. They answered they don't have the spare parts anymore for such an "old" model (purchased Nov. 2009).

I managed to remove the switch, then tested it with my multimeter: it seems to work fine (legs are indeed in parallel).
Then I removed the upper board, by de-soldering the two wire ends.
I then put a battery in, and used the two wires as a switch, which resulted in a first successful attempt: short contact = light on at max level, long contact = low-mid-high.
But after a couple of such cycles, I got the same behaviour as before: the LED remains permanently on with very faint brightness. Subsequent contacts between both wires do nothing, and to switch off the LED I need to remove the battery. Then further attempts only lit up the LED at very faint level.
Therefore I'm afraid the issue is at the main board level, a completely unaccessible part, and whose repair would be light-years beyond my electronic skills.
Bye bye my H501R:mecry:, I liked your compactness and lightness so much that I had offered you a new, highly GITD switch booth.

bummer...

Cemoi said:

This was my first try. They answered they don't have the spare parts anymore for such an "old" model (purchased Nov. 2009).

Click to expand...

replacement?!?

http://zebralight.com/H502pr-Photo-Red-AA-Flood-Headlamp_p_175.html

@AstroTurf: yes I know the H502pr, but #1 ZL does no longer sell outside the US, and #2 I don't have a real need for this kind of light.
I hoped I could fix my H501R because it is so tiny and light (far more so than the H502), and I don't like to trash flashlights.

Ah, gotcha...

Hopefully ZL will reverse that policy in the future.