Fredxx expressed precisely :
You might be correct, but I couldn't think of anything representing a load that might be part of a PSU. Without trying to trace out the tracks, might CN3 be a mains on/off switch, or even a mains powered neon warning light?
I have a scooter and its SMPSU in the hut. That PSU has a cooling fan, I wonder if this unit also has one? The fan only runs when the unit is doing a rapid charge.
As so often you are in the NG, you are wrong yet again. You have done little to help the OP in this thread, other than try to wind those up who are trying to help him - much more noise than signal.
I think the general observation has been that the PCB may have been designed to take a surface mounted / traditional fuse holder (that would accept a std 20mm / 1-1/4") fuse, or (for cost savings), a wire ended fuse, soldered directly to the PCB, possibly in alternative / smaller holes.
Cheers, T i m
That's deep!
So you have Voltage regulation?
Why do you need an overcurrent limit? You already have Voltage regulation, so how can the current become excessive?
When you say the battery limits the current "much of the time", just how much of the time?
At what point does the battery stop limiting the current and why doesn't your Voltage regulation just reduce the Voltage to the point where you are not reliant on the environmental variables of the surroundings to influence current consumption?
AB
CN3 connects to the on/off switch on the outer casing.
might CN3 be a mains on/off switch...correct
Yes it has a cooling fan.
Out of interest a previous poster mentioned a fuse holder, I googled that and the one in the link appears to match the solder joints where the blown fuse is.
I think you will find they were made like that and were actually 'welded' (spot) in the factory. ;-)
Cheers, T i m
Do you think they make the wire-ended fuses by crimping these caps with leads to standard fuses? I can see that soldering directly to standard fuses might affect their construction in unpredictable ways.
I think that would only work for trickle charging. If you want to charge at a decent rate then the battery has to be charged at a somewhat higher voltage, overlapping what would be the fully charged voltage.
Do you have access to a DMM? If it has a diode test range on it it might be interesting (and as I believe has been mentioned elsewhere) to measure the 4 diodes to see if one (or more) are short circuit?
I recently repaired a multi-port battery charger that had two dead diodes around the same area and similar on a PSU board for a big LCD TV.
You might need to lift one end of any diode that appears to be short circuit in case it's other components showing up as a short.
Cheers, T i m
Looks like it is a time lag fuse; T denotes time lag fuse. F denotes fast acting fuse.
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.
It's interesting, not something that I have come across.
Not sure exactly how it would be done, probably using the terminal voltage after a small load resistance and then using a timer to ensure that charging was maintained for a significant period.
The terminal Volts alone couldn't be used as 12V batteries seem to be happiest being charged at 13.8V, settling to 12.6- 12.7 V on removal of the charger.
Although it,s a fair while since I played with batteries, I seem to recollect that 13.8V was the voltage measured at almost every state of the recharging process.
'Couldn't find anything via Google, one or two curves but really the charge Voltage is to a great extent dependent on the source resistance of the charger.
AB
As a temporary test you could just clean up the toasted bit of wire and wrap some fuse wire between the two, with a dab of solder if you want. If that vapourises there's probably no point sourcing and fitting the proper fuse.
Someone suggested earlier that a 100W lamp could be wired across the open ends.
That seemed a far more practical solution.
Not quite as practical as a minute or so with a DMM, but a reasonably sound approach to the problem.
Faffing about with bits of burnt wire isn't the best approach. When the cobble up fails to produce results its not going to be certain that the connections to the burnt bits were reasonably Ohm free.
Even in a valid circuit a high resistance connection can produce emsisions in the visible parts of the electromagnetic spectrum!!
AB
wrong on both points as usual
the keywords you're looking for are: lead acid battery charging
NT
Yes, they are quite common.
In the days before printed circuits became widely used, similar clips were fastened to a sheet of insulating material.
The design of the clip included a solder tag that the connecting wired were soldered to.
Yes - a lamp limiter - common practice for enthusiasts renovating old radios and TVs - especially TVs.
They usually have a bulb and bulbholder mounted on their work bench in series with the mains supply with a bypass switch to short out the lamp when they are satisfied that no damage will result.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.