Unusual Dynamo standlight problem.

[JohnL]

I have a slightly peculiar problem with the standlight on my Busch and Muller top line plus. It's not that it won't come on, it's that it won't go off!!

I press the little tab on the back and it switches off as it should, then aprox seven seconds later, it switches itself back on! (Front light is definitely off at this point.)

It's not a major issue, it just means it has to re charge again when I set off, and I'm a bit worried it may cause issues at railway stations. It has only just started happening, it seems to be since I cleaned it. It is on a Brompton so is upside down when the bike is folded, I'm wondering if some water may have got into it after I folded it after the clean....

I'm gonna try some contact cleaner squirted in tomorrow to see if that helps, but I was wondering if anyone else had had any similar issues and had a solution. I'm not sure how the switch works so I'm not sure if it's a mechanical or electrical problem.

Thanks for any help!

John

[rofan]

I press the little tab on the back and it switches off as it should, then aprox seven seconds later, it switches itself back on!

Do you hear a click pressing the tab? How long do you press the tab. Did you try longer?

Usually the capacitor in the top line plus gets empty within a second pressing the tab. With the tab you make a connection between "+" and "-" of the capacitor.
But if the contact is not very good (humidity) some charge stays in.
I know that from the bumm 4D-light. There were only two contacts outside to get the capacitor empty. If there was no good connection between the two contacts, the LEDs started glowing again after a few seconds.

Maybe your tab has a contact problem, which comes from cleaning.

So pressing for a longer time and/or waiting until its dry again could be a solution.

[edocaster]

The switch probably empties a 'small' capacitor (small compared to the supercapacitor which actually powers the standlight). A robust electrolytic capacitor can take the strain of being discharged in a second, whereas a memory backup supercapacitor generally can't (or won't - the internal resistance is too high to be discharged instantly). The small capacitor controls whether the standlight is on or off.

When the bike moves, the small capacitor is almost instantly refilled, hence switching the standlight back on.

Your problem sounds like the small capacitor is being held up by a capacitor in another part of the circuit, possibly due to water ingress. Dry it out and try again.

[rofan]

The switch probably empties a 'small' capacitor (small compared to the supercapacitor which actually powers the standlight).

tks.
that is very intersting and new comparing with the 4D.

The "red part" leads to a micro-push button.
You can see the two round capacitors

[JohnL]

The switch probably empties a 'small' capacitor (small compared to the supercapacitor which actually powers the standlight). A robust electrolytic capacitor can take the strain of being discharged in a second, whereas a memory backup supercapacitor generally can't (or won't - the internal resistance is too high to be discharged instantly). The small capacitor controls whether the standlight is on or off.

When the bike moves, the small capacitor is almost instantly refilled, hence switching the standlight back on.

Your problem sounds like the small capacitor is being held up by a capacitor in another part of the circuit, possibly due to water ingress. Dry it out and try again.

Aha! That makes sense. It was doing it again this morning. It should be dried out as it is stored inside, I'll give it a good dose of contact cleaner this evening then if needs be will open it up this weekend. I have another older one that's bust to practice on.

Cheers!

John

[Elizabethsdad]

I have never got the standlight on my topline to work. It came with a new bike from Rose bikes. I know I could have got it sorted under warrantee but I didn't want to be without the bike and it wasn't that big a deal for me, I should say it is only the standlight function that doesn't work lights up fine on the move.

[edocaster]

I have never got the standlight on my topline to work. It came with a new bike from Rose bikes. I know I could have got it sorted under warrantee but I didn't want to be without the bike and it wasn't that big a deal for me, I should say it is only the standlight function that doesn't work lights up fine on the move.

All these reports of failures on B&M tail lights are slightly worrying. It doesn't seem to be the most competitive market.

that is very intersting and new comparing with the 4D.

The "red part" leads to a micro-push button.
You can see the two round capacitors

ElecTopLibrkl.jpg

That was a lot more complex than I was expecting. I was taking my cure from http://martin-jones.com/2014/02/07/herr ... ification/ - but the 4D seems to have many components, including a chip? Other than the big standlight cap in the middle, there's an aluminium electrolytic cap on the left, although that might just be to smooth the rectifier, and then some smaller ceramic caps (no idea what they are for).

[JohnL]

Just to update people.... The contact cleaner worked. I'll be a bit more careful when cleaning next time!

John

[honesty]

I had 2 standlight failures on toplight lights. Both within the first week on installing them. The supercapacitor became unstuck and sheared off (well it moved around when you wiggled the light!) which meant that the standlight never worked when I stopped. I returned it for a second time and got a replacement from another manufacturer.

[stewartpratt]

Wait… you can discharge these things? Handy (I take mine on the train every day). Am I right in thinking the Seculite and Secula don't have this feature? (I have a Toplight of some sort in the spares pile, but currently nothing I can mount it on.)