Anyway, I should get voltage read on the output with or without a load.
So something is definitely wrong with it 🙂
So something is definitely wrong with it 🙂
Yes, something wrong. Ac voltage is correct for this smps? I remember some old atx psu had voltage doubler switch (110/220V) and two varistors. High side capacitor was not a single, but two in series, and each varistor was in parralel with own capacitor. They were blown in that psu. Maybe yours have them too? In photo are two caps near diode bridge. Maybe those caps are connected in series and connected to diode bridge? Check for a jumper , from caps midpoint.to ac input. Jumper must be removed if using ac 230v input, and installed , if 110-120v.
Maybe it should. Your SMPS already has a fuse (T8A). The brown-red rectangle. It prolly is universal for 94-264 VAC so you can simply halve the value for your additional fuse (T4A). T2A is just not enough. As for the DBT keeping on glowing, that could be the design of the dual rail PSU. Which would be crap but not fatal. Measure idle power with one of those cheapo energy meters. Then check it against the specs.
What's the power factor of the PSU at full load? I don't know the specifications of the mains in Sweden, but assuming it's 230V±10%, then at the minimum voltage of 230 * 0.9 = 207V, the current would be 2A at a PF of (300 / 207) / 2 = 0.75. If it's any lower than that, the fuse isn't even guaranteed to not blow under normal use, regardless of inrush problems (and I ignored efficiency, which will make it worse).
Actually fuse don't blows so fast, it's parameters are not well guaranteed. If there are short pulses of overcurrenr, fuse will not blow. Another case when fuse will blow, if active power factor corrector is present . Then very high current is drawn with lower mains voltage, and at turn-on moment, if psu has no startup delay.
From photo isn't clear what is control ic. But i don't see second big inductor ( apfc circuit) ,so assume there's no booster. As it have internal fuse, try to connect it directly. If circuit breaker trips of internal fuse blows, then it's faulty unit and you should open dispute and ask for another . When you get replacement, remove pcb and test components, and can have spare one after repairing it. Do you have electric kettle 1-1,5kw ? It can be used in place of lamp , while testing smps with no load.
A fuse probably won't blow until quite a lot above its rated current, but it's only guaranteed to not blow up to its rated current. You don't want to normally be operating in that range of currents between the rated current and the minimum current where it's guaranteed to blow - maybe it would work indefinitely at, say, 2.5A, or maybe it would blow after an hour or so.
Exactly. The more times fuse rated current is exceeded, faster blowing up. In smps inrush limiting resistor must be present, or complete schematic, which slows down capacitors charging process and then short circuits the limiter ( resistor or ptc), when charging is done. Simple ptc resistor is cheap and simple, but when device is operating, then turned off and on again quickly, limiting don't occurs. Or.when mains voltage disappear for a short moment, and then appears back. This psu has black ptc resistor, but i think it has just few ohms, and with mains voltages like 230v inrush current still able to blow fuses, and cause arcing in power switches or by just plugging mains plug into socket.
Guys, just so we are in the clear.
The consensus is that the PSU is broken, right?
It can't draw enough to light a bulb without a load.
The consensus is that the PSU is broken, right?
It can't draw enough to light a bulb without a load.
It's clear that psu most probably faulty. But for me it's interesting, what's exactly failed. Recently had similar issue, makita tools battery charger . Power ic was replaced, output voltage was connected to dmm, ac input through lamp 100w. Lamp stayed bright, but dc output was 10V . First idea-bad diode bridge, one of diodes, but all four diodes measured good, one direction only. Later measured ac input itself, 300 ohms . Hmmm. Filter capacitor?? Removed , same. Varistor? Removed, same. Diode bridge , but how ? It appears diode bridge, from dust or something else , burned between ac input pins. Connected another one, ac input through same lamp, after one second lamp became dark, dc output good. Strange fault.
No, not until I've seen a figure for actual power draw. Besides, some PSUs go into some latchup mode when driven with a too low voltage. Get that toaster and use it as DBT and measure the current it draws. Or use one of those wall socket plug energy meters. Also, it has an 8 A internal fuse which will blow if it is truly fatally defective in any case.
Edit: there is no spec for input voltage range but it is intended for 230 VAC. See here
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I find it surprising to see that only in post #26 it is specified what power supply this is. Does the OP think we are clairvoyant?
Anyway, every chinese SMPS has a sort of fuse directly in the phase line. It is either the very first component in the line, or the one right after an inductor. That means you can safely connect the mains directly to the L-N wires. Without your own fuse.
DO however connect the PE line to the FG.
Be prepared that your house breaker will trip. It is nothing serious but you want to save your files on your PC because you can get a power outage.
The power supply cannot be broken. If it were, the on-board fuse has already blown and it would not blow your 2A fuse.
I am thinking more about one of the filter components in front of the on-board fuse. Either between L-N or between L-ground or N-ground. In this case it can be repaired. But given the electronic skills of the OP I am reluctant to recommend that. After all these are dangerous voltages.
Once you build your device or amplifier do put your own fuse in your device. But obviously matched to what is needed.
Anyway, every chinese SMPS has a sort of fuse directly in the phase line. It is either the very first component in the line, or the one right after an inductor. That means you can safely connect the mains directly to the L-N wires. Without your own fuse.
DO however connect the PE line to the FG.
Be prepared that your house breaker will trip. It is nothing serious but you want to save your files on your PC because you can get a power outage.
The power supply cannot be broken. If it were, the on-board fuse has already blown and it would not blow your 2A fuse.
I am thinking more about one of the filter components in front of the on-board fuse. Either between L-N or between L-ground or N-ground. In this case it can be repaired. But given the electronic skills of the OP I am reluctant to recommend that. After all these are dangerous voltages.
Once you build your device or amplifier do put your own fuse in your device. But obviously matched to what is needed.
Well, I had a bit to many balls in the air at the same time so I forgot about posting a link.
It happens.
But I don't plan on doing any operations on the smps itself.
And Jean-paul.
There is actually an explaination for the sloppy soldering. Shitty solder, I just got it and the crap doesn't melt as it should.
When I actually got them to stick I had the choise of removing everything and redo or just try the amp first.
The PCBs are way better soldered 🙂
That said, thanks for your contribution.
It happens.
But I don't plan on doing any operations on the smps itself.
And Jean-paul.
There is actually an explaination for the sloppy soldering. Shitty solder, I just got it and the crap doesn't melt as it should.
When I actually got them to stick I had the choise of removing everything and redo or just try the amp first.
The PCBs are way better soldered 🙂
That said, thanks for your contribution.
No thanks. You soldered connections meant to have crimped faston connectors. 4.8 mm Faston connectors I think.
Shitty/sloppy work is shitty/sloppy work whatever the explanation. There is also no good enough excuse for bare wiring.
That having said, are you sure you interpreted the IEC connectors pins right? Just suppose you take L for PE. Had it too with cheap chinese IEC connectors that were simply confusing.
Shitty/sloppy work is shitty/sloppy work whatever the explanation. There is also no good enough excuse for bare wiring.
That having said, are you sure you interpreted the IEC connectors pins right? Just suppose you take L for PE. Had it too with cheap chinese IEC connectors that were simply confusing.
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I will redo the socket wiring.
The socket pins are correct, they follow the standard. The socket has both fuse holder and power switch integrated so it is hard to switch them up.
The socket pins are correct, they follow the standard. The socket has both fuse holder and power switch integrated so it is hard to switch them up.
It were similar IEC connectors with integrated fuse holder and switch and those pressed rails. It was quite easy to mix them up and cause a short. Just pull the plug and use a DMM to measure the pins.
Also check the SMPS L, N and PE if there are no mistakes/mixups.
(You did not connect the secondary GND to the case/PE did you?)
All good? Then use a 4A T fuse for testing. Träge but Fast as lightning with a short, otherwise heavy enough for the intended power.
Does it function like it should or not? Report back and many will give advice how to continue.
Also check the SMPS L, N and PE if there are no mistakes/mixups.
(You did not connect the secondary GND to the case/PE did you?)
All good? Then use a 4A T fuse for testing. Träge but Fast as lightning with a short, otherwise heavy enough for the intended power.
Does it function like it should or not? Report back and many will give advice how to continue.
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