On Thu, 01 Feb 2018 19:29:19 +0000, Terry Casey wrote:

In article , says...

I have ordered a fuse from ebay, Yes I will try that Harry as it may
well be something on the scooter that is at fault although I doubt that
as the scooter was being used until the batteries failed, who knows.

The scooter itself works ok as I replaced with new batteries.

You might not have ordered the correct fuse, I'm afraid.

I've just been taking another hard look at the picture and I'm now
convinced that there *is* a fuseholder, though not like anything I've
ever seen before.

If you look carefully, the botton end cap appears to be sitting in a cup
and I think that that is the other cup on the end of the wire - look at
the height of it compared to the width - its much less than the length
of a fuse cap!

It isn't easy to scale, but I reckon it is a 20mm fuse so a mains fuse
is too fat to fit the cups. It might also be useful to know excactly
what is engraved on the remaining end cap if I'm right, you should be
able to just pull it out.

Oh, and measure the diameter of the cap as well.

I've been following this thread, not having followed the link to the
posted photo until now, and two things have become rather obvious from
that rather restricted view of the PCB showing the fuse and its close
proximity to what appears to be a mains voltage rectifier diode bridge.

Firstly, that fuse *is* a standard wire ended glass fuse[1] intended to
be soldered onto the PCB of a SMPSU and secondly, the small section shown
of the PCB looks typical of the mains input section of a cheap SMPSU
(there were no EMC filter components in evidence).

In theory, even cheap SMPSUs include overload protection so shouldn't
need to rely on a user replaceable fuse for such protection. However,
since even the best quality SMPSU can't be guaranteed against failure of
its high voltage switching transistor(s) which tend to go spectacularly
short circuit rather than go silently open circuit like a fuse, such
soldered in fuses are a mandatory requirement in all such SMPSUs
regardless of the expense of their manufacture simply to ensure that they
don't go up in flames and set light to whatever premises they're located
in.

Very few manufacturers would be willing to take the risk of a criminal
prosecution of Arson or Manslaughter (although it would seem that when it
comes to cheap knock off USB phone chargers, there are some who take a
more relaxed attitude to the risk of Manslaughter by electrocution).

In short, the reason for the soldered in fuse protection is to protect
against the fire hazard when (rather than if) another soldered in
component, the mains voltage rated switching transistor, blows short
circuit. The mains voltage fuse is deliberately made a non user
serviceable part simply because there's no point in replacing it without
replacing at least one or more other soldered in parts.

If the OP does go ahead with his plan to try testing it by powering it
up after soldering in a replacement fuse, all he's going to get for his
pain is a repeat fuse blowing event.

[1] Such glass wire ended fuses are typically wrapped in heat-shrink
sleeving to prevent glass shards being sprayed around the interior of the
PSU due to the very high fault current that is produced when a switching
transistor goes short circuit.

--
Johnny B Good