This is a generic imported CCTV power supply bought from eBay. There are a few issues with it, mainly the quality of manufacture, electrical isolation and wire colour choices.
The large holes to allow a wide tolerance of the mounting pillars may shunt the positive rail to ground if too far off centre. If that happened and a circuit had the negative referenced to ground elsewhere it could result in quite a high current flow without any inline protection. Some insulating washers on the case mountings would avoid that.
The poor electrical clearance was completely avoidable. The Chinese manufacturers don't seem to be too fussed about separation between high and low voltage. Swapping the live and neutral would reduce that hazard, but that's a bodge fix.
The spare PTCs were puzzling until I saw how splayed the legs of the PCB mounted ones were. These components cycle thermally in use, so that may result in stress on the lead connections.
The switchmode power supply is a joy of complexity, with its low voltage controller chip controlling circuitry that has strong self-oscillating ballast type vibes. It almost looks like the unit starts self-oscillating to power the output and control circuitry, and then gets its feedback transformer magnetically shunted or controlled by the low voltage side.
I'd like to see a schematic for this unit. Reverse engineering it would be made tricky by the two custom wound multi-winding transformers.
It's an interesting unit, but not one I'd trust for a safety critical application.
Incidentally, the first cable I tested it with turned out to have a three pin plug and socket, but just two core flex connecting them. It was supplied with a studio light from eBay.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty.
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The large holes to allow a wide tolerance of the mounting pillars may shunt the positive rail to ground if too far off centre. If that happened and a circuit had the negative referenced to ground elsewhere it could result in quite a high current flow without any inline protection. Some insulating washers on the case mountings would avoid that.
The poor electrical clearance was completely avoidable. The Chinese manufacturers don't seem to be too fussed about separation between high and low voltage. Swapping the live and neutral would reduce that hazard, but that's a bodge fix.
The spare PTCs were puzzling until I saw how splayed the legs of the PCB mounted ones were. These components cycle thermally in use, so that may result in stress on the lead connections.
The switchmode power supply is a joy of complexity, with its low voltage controller chip controlling circuitry that has strong self-oscillating ballast type vibes. It almost looks like the unit starts self-oscillating to power the output and control circuitry, and then gets its feedback transformer magnetically shunted or controlled by the low voltage side.
I'd like to see a schematic for this unit. Reverse engineering it would be made tricky by the two custom wound multi-winding transformers.
It's an interesting unit, but not one I'd trust for a safety critical application.
Incidentally, the first cable I tested it with turned out to have a three pin plug and socket, but just two core flex connecting them. It was supplied with a studio light from eBay.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators
LOL at the thumbnail
Clive unlocked it twice to prove it wasn't a Fluke. 😂
That pcb is clearly not a mass production and the whole thing seams hand made to the exception of the psu.
Thanks for the lock picking entertainment and it was also very informative. The next time I'm at work having to deal with opening a box I'll give the pick a try before looking for the keys only to find out no one knows where it is and safe my drill bits ant time replace the lock 😅
I'm "shocked" that Clive didn't say anything about the mounting instructions mentioning the "Buttom" 😂😂🤣🤣
Kept thinking you were saying soda, instead solder… I was like damn the builders were messy
Oh yes that power supply looks like a fairly standard unit. I picked up one a few years ago with the intention of putting all my networking gear that was 12 V on a centralized power supply and well I'm only just getting there now. I have essentially turned it into a central battery with it feeding some radios and socket for plugging things in and Anderson cables to three Anderson breakout panels. I have it set up to charging some 12v5A SLA batteries like nine of them in parallel ( I had a large UPS that I replace the batteries in all at once as one of them exploded. but all of the other 9 were still good. Unfortunately not long after the entire UPS died catastrophically with that transistors which I tried to replace buying new components off Amazon that ended up being used, but still not sure that's the only issue with the board gave up and bought another unit ). I wired it up through some diode's and that splits two ways to a board that shuts off the batteries when the voltage drops and then that goes into a Buck boost regulator to put out stable consistent 12v until the battery protection module shuts off. It's been sitting there on ( like a Frankenstein project with life support cables ) for at least 3 or 3 years now with the occasional power outage. I think I went with the 35A module?
I think the power supply you're showing here is based on an CLL Resonant Converter. An old but still in use switch mode power supply, much harder to understand than usual DC-DC converters. You can google "steigerwald 1988 pdf" if you wish to start going down the rabbit hole…. Professor Sam Ben-Yaakov also has a lot of excellent videos about it on YT and TI has some good literature about it too.
The windings connected to the transistors are probably there to be able to drive something connected to 340V from a low voltage supply (12V?, 5V?), offering galvanic isolation as an extra benefit to the control side.
How the all thing powers up I have no idea… it's "magic" 🙂
almost 40year old design TL494 7500
Who'd have thought? This doesn't look like a very good product!
The isolation issues on the PCB can be obviously made irrelevant by simply connecting the incoming AC flex from the IEC socket directly to the power supply terminals. The silly switch on the board is completely unnecessary given the fact that you can just unplug the input power at the IEC connector to turn off the power.
I have a 5V power supply that looks almost identical to that one inside. I didn't look at component values or even the back of board but at a glance I only noticed a few very marginal differences: the bridge rectifier is a single component, a single higher watt resister near the large electrolytic caps instead of 2, 3 jumper wires in the middle instead of 1, and the 3 blue caps near the input/output connectors are on a diagonal.