Hi welcome to Tear down! Tuesday We've got a power supply for you. It's a KO read I Hadn't heard of Ko Read before either, so no surprise it. Apparently they've been around for quite some time and they make some high-end specialize power supplies, but this is one of their bottom of the range low-end programmable one. It's the KA Three double O 5 P 30 volt five M programmable power supply And it's really cheap.

So I don't know when they're really cheap like this. You got to wonder what's inside of them. So let's take a look. And thanks to Charles at Trio Smart Cow who are the Australian distributors for this thing, they just got it in its new.

They loaned me one so what kind of? Take a quick look at it? You know we say you're on the Eevblog, don't turn it on, take it apart and we'll have a quick peruse of the outside here. It's a single output supply of course 30 volts, 5 amps. It's got that programmable memories it's got. It's a floating output of course, plus your ground terminal here.

It's got your optical encoder knob here, voltage, current control over voltage, over current protection, output on/off switch, lock in memory recalls, various status indicator LEDs and separate voltage and current readout displays. It's got everything happening and if you can tell it's a linear supply by the weight of it, trust me and there's a big whopping transformer in there, you can probably see the yellow tape around the core. Let's have a look at the back here. We've got standard: IEC mains input connector it's only at 220 / 240 volt.

There is no selection switch. there might be one inside or there might be a transformer tap or something like that, but certainly it's not going to work off the bat with 110 volts as you'd expect with the linear supply, it needs those transformer taps and we've got our presumably Rs-232 serial and USB interface. So there it is. Then we're going to fan as well.

and that's about it. So let's crack this thing open. Few screws on the side. It's a, you know, a reasonably thick metal chassis.

it feels, you know, it certainly does, is a feel cheap and tinny like some of the others I've looked at. So let's try and get these screws out and see what we've got. Alright, I'm not expecting a huge amount inside this. I'm expecting a large amount of empty space, a big transformer, maybe a board here, and a board over here.

and that's about it. There'll be Control, Board maybe the Power Board and they'll probably be a display board as well. So let's get this thing off and Tada and let's look at the chassis first. Of course it's your traditional are just your bent folded metal frame like this, they've just, you know, folded at the sides and then pinched it and fold the edges fold over.

and they've got these support bars on the top like this. And rather interestingly, they've got another plate across here which doesn't really seem to do anything in terms of you know, maybe you know, electrically sort of. You know, a bit of shielding perhaps from the rear side to the front, but gee I don't know. It's more like it's a more like it's a you know, a cross brace support really or basically a dual function there.

But as it stands, the thing does, you know it's reasonably rigid I guess for us for folded metal case like this so it's not too bad and at first glance it's a nice and neat and tidy. I Guess the only thing I'm going to really complain about here is that this stiffener bar up the top goes into a plastic surround. It doesn't go into like the you know, a metal part of the folded front panel. so it's not a complete metal frame, just plastic bit.

You know it feels solid enough though. So I don't think too many problems. and if my eyes don't deceive me, this top bar here actually slopes down. This is not square is it may not.

I may not be able to capture that with the wide-angle lens. So I'll go back here and see if I can zoom in like that and this seems like it should have been mounted flush or on top of this plastic support. here. it's just not not square, it just looks funny.

and I don't know what's going on there I think they really kind of goofed sort of rushed the design of the case there and sort of goofed and went whoops. We'll have them sort of mount it on the bottom side of this plastic stand off. Weird. Let's have a look at the mains.

Warren Here we've got our fused IEC mains connector over here. It's a solidly connected down to the case there with a like a stand off on the case. but there's no shape proof washer on that that I cannot see. but it's certainly is that very tightly done up.

It's all heat shrunk and there is no 120 volt tap on this thing. In fact it's up marked you know to 40 to 30 volts 5mm so it looks like I'm yeah, just be careful where you buy this thing from. it is not switched at all. and of course we've got a real power switch clunk and power switch on the front which actually switches in the mains primary like that and it.

You know it's all neat and tidy. It's all here. Trunk: I Like it, but for holding down the transformer under the base there, it does look like it uses some form of shape proof washer under there. so thumbs up to that Now system design wise.

Basically it's got a separate USB control board down there. We'll take a closer look at all these boards in a minute, but a separate USB control interface which then goes over by this cabling. up here up It's cable tied up here and goes over to a some sort of processor and display type. Or there's the display.

The actual 7-segment display board is on the front. Then there's another processor board here, which would be the digital control and that's probably like a serial interface over to there, so it maybe that's just a. The USB board is just a you know USB to our Rs-232 serial. And then we've got a separate to power board over here with the separate heatsink on the back bolted under the fan which I'm I Don't think I've seen that particular construction before, but it's actually quite clever and we'll take a look at that in detail.

Got a separate little board down there on the front panel binding posts. so let's take a look at each board in detail now. just interestingly here, just above the processor board. they've got a cutout for a big D 25 by the looks of it, so they didn't go ahead with that.

They've gone for the D 9 plus the USB. Now this is interesting on the USB board. Here, you'll note this big whopping earth wire here. Huge out, you know, mains rated cable.

So we're talking you know, 10 amp rated cable soldered directly onto the top case of the USB connector, going down to a shezzy standoff down in there. and of course, which of course that goes through the chassis and over to the back to the mains IC input connectors. So that means most definitely the USB connector is very well and truly Mains Earth connected. Why are they done that? so that you don't have any issues with connecting this to Mains Oh went to your PC which will also be Mains Earth reference and you can see some optocouplers on here.

So this is actually an Opto isolated our USB / Rs-232 interface. Brilliant Sites Mains Earth on the USB and the serial side presumably. but it's not. But then it's isolator which goes over to the main connectors.

Brilliant. They've done this properly. I Like it. and of course, to power this board, you could of course that power it from the 5 volt USB But if you're just using the Rs-232 there, then you know you're not going to.

You have to get that power to the board. So they've got a separate tap on the transformer here with look, what looks like, um, there's a round device in there which is most probably some sort of a moth I would guess and that's up. and that's powering the board. You can see the bridge rectifier in there and some large filter caps as well.

Nothing. I'm going to revise my estimate on that one. I Think it's a some sort of choke. You can feel the windings in there around a around a little toroid or something like that.

So they've yet. they've decided that they need that in line with the output of the transformer tap. And here's the USB board in some detail. And of course, the first thing you notice is that the bastards have scratched a number off the chip.

Give me a break idiots, Why bother? It's just ridiculous. It really is. Anyway, a couple of four and twenty five up day couplers there. There's the bridge rectifier we've got to filter caps which are Z-h brand never heard of them, but they are a hundred and five raided, and a couple of little like power devices.

They're probably some sort of regulator there you one and another power D pack up there crystal which isn't isn't glued down at all and a another 32 kilohertz or presumably 32 kilohertz watch crystal also just floating in mid-air there. that's that's not good. I Don't like that bill. that's a bit of a fail.

I Should stick that one down properly, but you can see the Big Earth connection to the Usb and apart from that is that you know it's a pretty mediocre they've got to budge cap on the input there. That's a 470 nano farad hundred volt job. And yeah, there's not much else doing there, so let's get a bit of spit put on that see if we can. Yeah there.

well and truly rub that off. I Think yeah I'm not seeing anything there that's that's familiar so your guess is as good as mine. Now let's take a look at the power board here, how it's actually mounted. and as I said it, rather like this: It's um, you know it's there's the power devices down in there, presumably the power transistors and they're mounted directly onto that heatsink and then the board's mounted onto that directly mounted on to the back of the fan.

It's a rather efficient I'm kind of mounting their manger I Really like it. You can see all the well, the heat sink, compound, or smear down in there behind the devices, but that's that's really quite neat. And of course, that should keep most of the heat away from the main filter cap. Here, it should, you know it.

It should be a reasonably efficient system to actually remove the heat directly from that heating. And the main filter caps are 63 volt 6800 micro farad. It's got a vent, of course, big vent written on there, but I don't recognise that brand so I'm not going to bother to go look it up. I'm you know it's only 85 degree C rated not that terrific.

Um, is held down with some hot snot. Here's some hot melt glue, so they've at least done that job. The the connector here more hot snot. There's generally on the power supplier that companies love to use hot snot.

They just feel you know they just apply everywhere inside these supply. so it's not uncommon when you open them to get maybe you can see it. They're just little leftover sort of strands of hot snot all over the all over the unit. This ones aren't not too bad.

I've pulled out a couple of little string ease in there, but not too much at all. Now as for the system architecture, in terms of the power cable, and of course, we've got our main taps out of the transformer here and they go down into the power board down in the bottom here. and then the output from the Power Board is a couple of relays on there. We'll take a look at that, output from the Power Board goes directly into this main board, which we'll also take a look at which is clearly the control board and then it jumps on over.

It goes up through this current shunt here through to an output here, which then goes jumps down to the output binding post there. So that is the that is the power part, the main power path in this design. Now offhand. I Don't know what these connectors are rated at, but you know 5 amps are.

You know they? they could have done better. It's probably just start, barely adequate for the task or the power wiring in here. Stuff like that, you know, but I guess you're sort of limited in this compact thin form factor like this - - exactly how he cannot lay out the board and stuff like that. Maybe if they use, move the transformer to the back, but then the weights not centered nicely.

they've put it in the center so it's all nicely weighted. But if you had the power board directly up near the binding, you know sitting on the bottom directly near the binding posts, that may have been better. and then you could have avoided. You know, having to do all of this wiring, jumping over to this processor board and then down to there.

But oh well, that's the way they decided to do it now. as is par for the course with these type of 30 volt linear supplies, they've got multiple watt taps from the transformer here. they've got three different taps and they've got two relays here and they switch in the taps when you get to a certain node voltage to reduce the power dissipation in the heatsink is because this isn't you know, a very big heat sink in the scheme of things for a 30 volt R5 amp power supply. So they need the software needs to know exactly when to switch those things in.

So as you turn the optical encoder knob and they get to a certain voltage, you'll hear those relays clicking in and out. And if we take a look over here clearly, the heatsink are contains a bridge rectifier There you can see the see the symbol there, so that's mounted on the bottom of the board and then that's mounted up under there, wedged between the heatsink and the board and then you've got your couple of power transistors there down in here like that? There they are. I'm probably not going to take this board out I'm not going to bother. I'm not that interested to find out exactly what those power transistors are not very interesting and a free-standing to-220 device here.

Not a big fan of those and rather it be strapped down. but I get that all the time. Now taking out the main control panel, our PCB here. take a look at the front side components.

There's two board to board headers here. they're why they've got a male and female there I Don't quite know, but this bottom part is that rather interesting. It deserves some looking at and if you take a look, this is clearly the power part where I showed before how the power comes in here and also it comes in here and goes out over here down to the front panel binding posts. So this comes from the power board input and down there.

and you can see note the tenon on the traces through the solder mask. there. they're deliberately left off some solder mask and they've put 10 in there, presumably to increase the current handling capacity of the traces. because there's you know there's two ways to increase the current handling on a PCB One is to use what three ways.

one is to use wider copper traces of course, but you've only got you know you've only got so much room in here. they can only be so thick. Another is to increase the copper thickness. A standard board might be one ounce, but you might go for say two ounce or even more thick copper.

But that cost money. You know, coppers expensive. They want to keep the cost them. So a third option is to just start in it because they've got to what's older.

They've got a wave solder this thing anyway, so why not leave some solder mask off? Apply the tin in there, and that effectively is a cheap way to get yourself extra current handling on your traces there. and that's clearly what they've done. It's all a bit. It's all a bit boggy around here, but all these holes, you notice all these slots here.

These are presumably they look like, so they've you know, high voltage isolation slots. But look at, you know, Why go to all this trouble when you've got these tiny little traces snaking through to here that's going off to a connector somewhere? I'm not actually sure that's doing at first glance. I Got a whole bunch of these holes around here for for our airflow over the heatsink, the heat sinks on the other side of that board. so they've got some heat flow there, and you know that looks like it's a high voltage isolation slot that one as well.

But yeah, once again, I don't quite understand it when the trace is up there right next to I Don't know. Weird. Maybe it's all just you know air flow. And if we have a look at the main board here as I said power comes in here from the power board.

We've got our current shunt here, which is, you know, just a dodgy coiled a bit of current sense wire. There's a diode in there, a couple of filter caps, and power just comes out here to the front panel binding posts, and then we've got a power device in there. We'll take a look at that. that's a seventy eight one two.

so that's just a yet twelve volt voltage regulator on a time. Little heatsink. got a buzzer. Another couple of power devices down in there SOT 2 - 3 s.

One of my favourite packages and one interesting knife feature which you'll take a look at is a whole bunch of 7 for H C59 fires with all these resistors here. and it's rather curious because there's not enough output connections for all these resistors. We'll take a look at that. Another process of idiots.

they've rubbed the number off again. Another device down here there. The number of. ah, nuts.

Anyway, that's clearly some. You know that some sort of microcontroller? Some little 8-bit microcontroller. Probably nothing fancy at all. Probably a few Watt comparators over here.

Let's take a closer look and we've got three. TL o eight - Is there a little bit of a budge solder bridge there? I Think that's done on purpose, otherwise it most likely wouldn't work and the odd component left off there. but that's probably something to do with. you know, the over voltage over current protection stuff.

and they're too cheap to fit a zero ohm resistor there. So yeah, just bridge it out and this one's a real hoot. Take a look at C 14 there. That's the weirdest capacitor I've ever seen.

Is that 1k Farad's micro? Farad's beaker? Farad's puffs? What is it? And then we have a classic U Ln 2 W 3 Darlington driver and there's an Atmel L7 4 HC 64 squared external a squared from there. So whatever microcontroller they're using obviously doesn't have any built in a squared problem because you know this thing doesn't need to hold a whole lot unless it's a doing data login which then uploads to the PC but I didn't think it did that I Thought it would just upload data in real time, but err, to scratch the bloody numbers off again. Now this resistor network here with the Sim 4 HC Five Nine five. This is one of the most unexpected things in here and it looks all the world like it's a pro.

This is the DAC It's a programmable resistor ladder DAC of some description I could go through and you know to actually reverse engineer it and figure out exactly what they're doing there. but I believe that's what it is. go figure. I Guess up 3, 7, 4, HC, 5, 9, 5 and a whole bunch of resistors is cheaper than a real DAC And behind the main that processor board here is a Saida board.

See a couple of jumper links here. that's for the soft buttons on the front and they've God will be the trouble to do the optical rotary encoder over here on its own little board on its own little standoffs which then goes through this head up onto the soft button board which then goes through this, head up back to the main processor board go figure. and the processor board is actually straddling the display board as well. So there's the other header up here which plugs into the display board and then this header down here which plugs into the soft button rotary encoder board.

So that's it. You know they've gone to a bit of trouble there to make sure all that stuff lines up across all these different boards and we're going to budge. Why are there oops and down on the binding post board? There's not much doing here. You can see the one kilovolt caps connecting earth through to the negative output.

Their standard practice: they've got a proof washers on the nuts and behind the nuts for the binding post. They're nice. They've only got a small amount of output capacitance because on Am on a constant current power supply. of course, you don't want a massive amount of output capacitance because then that energy can be dumped into your circuit when you don't want it to be.

And then we've got the the main input site here of course, coming from the output of the current sense resistor on the processor board. And then it looks like they've got a another little light sense cable which senses the voltage directly at the output terminals. Nice. So there you have it.

The Co Rad Ka3 w5p programmable DC Power Supply Yeah, why can you say it's a cheap Chinese power supply and it's I Guess you can say it's not bad. for the cost, it's pretty much what you'd expect par for the course, but the cleanliness of the PCB and the solder joints leaves a lot to be desired. Doesn't instill a lot of confidence quite frankly, But for the money, yeah, it's not too bad, what do you expect? But anyway, if you want to discuss it, jumping over to the EUV blog forum if you like Teardown Tuesday, please give it a big thumbs up because that helps a lot. Catch you next time.