I was sent this illuminated Tetris ornament by Ray who had received it as a gift and the idea is that these bricks have chromium plated plastic edges and when you press them together, they all conduct and it carries current through the thing. It's very flickery, but it does kind of work. However, while Ray was playing with it, he got an electric shock. and if you check with the meter, onto this base piece.

So let's start off by turning it to AC volts and I go to ground with one connection and put another connection on. Here it shows a voltage of about 220 volts. Okay, now if I turn it to the micramp setting I mean this isn't uncommon that you get a slight floating voltage on these uh, the Spectrum power supply powered devices. but if I turn it to the AC current setting uh, microamps and then I put it on the metal work, it shows a current of about 560.

eight micramps. but then when you actually bring other parts into play, it seems to boost that up a bit and then, well, there's 1.4 milliamps and that could deliver a significant electric shock as it did now. I Have done some basic tests in the power supply. It's not posing any immediate risk, but I wouldn't recommend actually using anything with one of these power supplies.

I Haven't reckon that. recommend these purse players all but especially not when you're actually touching it because it all it takes is being referenced to ground. You do it, and in some instances in this case you'll get a slight tingle button. The instances, of the pure isolation in these and we'll take that apart afterwards.

You could get a significant electric shock, but let's before. I Take the power supply part. let's take a look inside. One of These Bricks because it's quite a nice system.

It's quite sort of fun to play with, even if it does give little zaps. So so if I open, say for instance this brick here because it's one of the easiest to opens. It has two diagonal screws that has also got fake screws there and to open it, you have to take out the two long diagonal screws and then on the other side you have also take out the opposing diagonal screws that hold it together. Make sure these are all out and once you've done that, I'm trying to find where the real screws.

There's a real screw once you've done that. The construction inside is really, really simple and I'll take some pictures and show you some pictures of it. Close up. One last bit of screw.

so the chromium insert has I Wonder if you could pull that off? You know I Think it is glued on or clipped on, but it has two little pins coming inside. Actually, you know what? I shall pause I shall take some pictures and then we can continue one moment please and resume. Okay, I've got the images. So these devices have a little soccer board like this and when they're put together, there are these pads that go against the Chrome inserts that come through from these Chrome pieces.

But there's a little spring in that is shaped. Um, well. I've got another picture here. The spring is tapered.

it's shaped like this. a doom. and when you actually press the circuit board in, it just basically wedges behind that spring. and the spring itself actually seems to turn and then skid down the pad.

And that watch makes watch me what? That is what makes the electrical connection. So there's one of those on both sides. and it's notable that there's a single resistor 100 ohm resistor about two LEDs The reason for the two LEDs is that if you've got these bricks, they can go around either way and that means the Pilates could either way and rather than use a bridge right to Fire and drop a bit of voltage, all they've done is it's the cheapest way is just to have two LEDs in Reverse parallel. So no matter what a polarity is, that resistor will limit the current and only one LED will light.

and if we take a look at the other block the main one that provides power, I'll just put this little circuit board over there. Then we find this. We've got the incoming Jack socket. We have a switch.

We have a PTC thermistor which is rated about one amp and in the case of someone shorting the things out, won't you short the power supply continually? If the current is high enough, it'll actually trip this just for protection. And the circuit boards. LEDs They only have one LED It's just an economy thing. They know that the priority is going to be in the base because it's always going to be the same so they just have a single LED Strange.

I Would have thought they'd just use the double LED one anyway, but they have saved the cost of two LEDs in this base unit. Let me assure you, the schematic. Here's the schematic: I'm just to jump up and down here, just make sure it's in shot, different filming location so things are different. For me, Here's the Jack with five volts Command from the Dodge of power supply.

There is the switch. There is the PTC Thermistor which is basically a resistor that heats up when too much current flows and it basically goes High Resistance but it will self-reset Then we got those two LEDs circuit boards with their 100 ohm resistor each and then the contacts going out to the edge of the block. Every other block after that has the same thing. It's just got two of these inverse parallel LED arrangements and a resistor so that no matter which way around it goes, it will just basically light up and the position of the LEDs inside is just designed to basically try and illuminate as much of the block as possible from just two positions.

Okay, let's take apart the power supply and see what's inside. Cheapness will be inside. So I'll unscrew these two screws and we shall open this up and hinge it open And inside is a very classic little GP import power supply. Um, we've got the suppression capacitor there.

we've got the Transformer with acceptable but not great electrical separation and are probably open this Transformer too and we'll take a look at the winding separation in it just to see what it's like and just looking at other things than this. Oh, it's a single diode it's got, so they're really cheaped out here. That might be part of the problem. Um, and it's a discrete, uh, power supply with a single transistor here and a little surface mount transistor here in the feedback circuit.

Um, to actually kind of represent the voltage and output. It's basically a cheap five volt power supply rectangle. Rod I'm just going to break apart this Transformer and I'll describe what it's like one moment, please. it is.

Unwound Um, credible. Credit's due I Can't get in too close to this just because of the distance the camera is from the bench at the moment. But credit where credit's due. The secondary winding, which is sandwiched between the feedback and the primary winding, does have layers of tape separated from both those windings.

It's still not great. You know it's just a layer of wafer thin tape. A typical UK compliant or American compliance Supply would probably have the double insulated or triple insulated by a much thicker insulation, but in this case, uh, they've not crossed it directly over other Um windings, which is good. There's modest separation.

The class Y capacitronus is 2 200 picofar, 2.2 nanofarad Um, which is a typical value might find of these. So what can you do to make your Uh to make your Tetris safer? Well, the answer is at this cable. Chop it. uh, work out the party I Don't think you can damage it if you get it wrong, but work out the clarity and splice it on with a bit of air sleeving onto a USB power supply.

Because a typical USB power supply like say for instance this one, let me plug this in. I've got another little circuit board here. a typical Supply like this one. if I plug it in and power this bit of circuitry and I bring the meter back in again, it should display a lower sort of floating voltage.

Let me just uh, put this to AC mode, right? Okay as AC mode and I'll just tap onto this connection and stick it to Earth and in this instance of getting about half the means voltage about 96 which is fairly typical uh, but the current leakage current which is kind of more important if I go from here to here and I select microamps and I go on to this connection and I go to ground the current it shows. Let's see if we can get a connection here. Let's uh, select AC current. That'd be really good for leakage like this.

Um, it's about 123 microamps. Instead of the 10 times that that was giving tingles off the other unit, you can still get a slight tingle of a USB charger for phones. But um, it's not as bad as the original one. So there we go.

Um, it's a nice enough thing. It kind of works. It flickers a lot when you stack the blocks on top of each other, but with the original power supply I Think part of this might be the fact it's got a single diode on the input and also, um, just the capacitive coupling through this. the way the way it's designed and and the close intimate nature of the bindings.

Um, if you connect it onto a a conventional USB power supply, or if you're just playing in the short term, use a power bank then you're going to be able to play with this without the risk of those tingles, even if not in a grounded environment. I Don't recommend using these imported power supplies. These ones are just totally non-compliant with any standards except perhaps in China itself, so they just pose a hazard. Don't do it.

But all it takes is a slight manufacturing error or design defect and these things can actually put out means voltage to things that you're handling and where you've got the chromium conductive surfaces. You don't really want to make contact with stuff like that so use alternative. Uh Power Supplies Like good quality USB power suppliers but there we have it. the Tetris tingly Tetris blocks.

Now the power supply is well I'm going to change it and it will be non-tingly And there we have it. Interesting and very attractive little device.