Hi check out what I scored on eBay for 30 bucks a flute P.m. 28 one, two programmable power supplies. While these system power supplies are 30 volts, 10 amps up to 180 watts and I couldn't resist, it was an absolute bargain. Why was it a bargain? Well, this is actually how it came.

It's got no case on the thing and it was sold as like a parts unit working condition unknown so like they bought it and you know there's a few, like there's a loose board in here and stuff like that. But anyway, like I couldn't resist it for about 30 bucks I Thought we'd take a look at it and maybe see if we can get the thing going. now. this is actually a Philips design before Fluke actually bought Philips this was I think it's about a early 90s art vintage as if it's the 2800 series, There are different models available.

There is one which is much smaller. It's only like this Y which is the 28th one - it's only a single output channel one and you'll see why and they do that in a minute. It's actually quite modular and I've never used one of these before. I've seen him around but haven't had a look inside the thing and never use one, but you know it's it.

Philips made some good gear in this sort of art form factor so I have no reason to doubt that it's not a pretty decent quality system. DC Power supply and if we can get it working well. Bonus: I mean for 30 bucks, jeez, it's probably got 30 bucks with a parts in it. Easy.

and this is actually a modular, configurable power supply not by the user I Don't believe, but you can actually order it in every single output channel dual output channel or triple output channel like this one here is. and you can see why they sold a unit which is only this wide the 28 one - they just make the case a bit shorter. and they've only got the single output channel here so this is fully populated with the three output channels. And the good thing, if you're buying like you know, like maybe a parts unit on eBay for example, like solders nonworking, then it's good to get modular stuff like this because well, we've got three identical bottom boards like this.

We've got to identify top boards which look like utter though, the ADC board or some sort of process in tight board and it looks more. We're supposed to have three identical boards on there, but obviously this board here looks physically different to these two. but at least we have two. and it means that we can swap these boards over so we can swap the base boards over.

So be surprised if out of all these, we don't get at least one functional channel out of the thing. I'm just by you know, swapping boards I'd be quite surprised if like you know, there's a fault on every single one of these channels. so I'm not even sure if it's faulty at all. it may just power up and work just fine.

So having a modular type system like this very handy, especially if you haven't got the service manual for the thing. But thankfully we do have the service manual for this and it does have the schematics for almost all of the boards, but curiously doesn't have the schematic for this mains power supply here and this is actually our first issue. Now if we take a look at the back panel here, interestingly, this third channel here which has the boards in it obviously is not populated. so I don't know why.

Well, there is without one missing board up the back. Here we saw but like I don't see the function of having why you would need that board. any boards in there. populated law if you weren't going to have the connector on the back I mean we can just solder a connector on there as well.

See soon, there's a room to solder one of these terminal block connectors on the back. but anyway, very very strange into a GPIB interface of course. Interestingly, three little what look like I'm SMB Tiny Coax is down here for ready start and step so some sort of programmable thing actually I Just realize this why this board is different to this one here and this other one over here. Look, they've actually got a plate on here 60 volts 10m.

So this is a hundred and twenty what? This unit is capable of 180 watts total across all three channels like this. So we've got a 30 volt 10 amp 60 watt unit over here. 60 volt 10 amp by the looks of it. I Assume that you know when they configure this thing at the factory, they would have put the correct plate on there.

It needs both of those boards. Maybe they're 30 volts each and it needs both of them to give a combined 60 watt 60 volt output. Aha! I Should have thought of this before I started recording. Anyway, it's just dawned on me why they've got that extra board in there I Suspect and that actually makes sense if you have a look at the ribbon cable, they've actually got like a daisy chain ribbon cables.

There's quite a few daisy chained ones in it like cables in here, and they deliberately haven't put an extra one there. So obviously it wasn't designed to have three channels. But I think that's why this is actually I Believe a fully populated one that has 180 watts total output. But these two boards combined give a total as a 60 volts output.

And yet. Bingo! That makes sense down in here. - they've strapped these two boards together. There you go.

There's some Spade lugs on there and the output voltage is down. in here are strapped together like that, not in parallel, but they're putting them in series anyway. before I got sidetracked. There thing I wanted to show you is that up? Yes, it is 110 and 220 volts capable.

Supposedly it gives you the different ratings on there, but it looks like it's factory configured to a hundred and fifteen volts. So hmm. let's have a look inside. Now if you have a look at this mains switch mode board here, aha, look at this as a jumper link in there.

110 volts and 220 volts thank you very much. So you think uh-huh you just swapped that over to 220 volts there. But let's have a look at these caps now. These are very nice niche Econ caps spared no expense there.

Well, actually these are only 85 degrees C rated, which is a bit unusual why they didn't use 100 and not 5 degrees I Got no idea Anyway, I'm 680 micro farad's each, but this is why it's a bit cautious about thinking that I can just change that jumper over and I shall be right now, these are only two hundred working volts and if you're going to put this up to 240 volts, well, that's not good enough if these are in parallel for example. and same for these ones here. These are right. nip on chemi-con rather than use the same brand and run entirely.

Sure anyway, 200 and fifty volts. and if these are wide in parallel on the board, then one that's going to ruin your day. So I'm thinking that there is certainly a distinct possibility that this board, well, it does have that jumper on there. it may not.

It may just be that they supply the board for a hundred and ten volts and use lower rated caps in here because that's only a single wire jumping over. It's not like can easily configure in series and parallel combination on those caps. So hmm I'm just I want to get this board out and check what this jump is actually doing before? I Just walk it over there to 240 volts and and shove it in. I Don't want to blow the ice out of these caps that are ruin your day I'm Interestingly, they've got a yeah nice and big ass heatsink just flapping around in the breeze there on top of that diode bridge under there thing.

I Really like about this is that they've got these are sliders in here. the sliding support posts. you can just look slide those across like that and then they just pop out. Boom Ah well, close to it anyway.

Ah, probably should have taken the cables off first, but yeah, they just pop out. Very nice. We've actually got a manufactured date code on this 1996. There you go for the border here.

You got to love the tin copper traces there for increasing the current handling. Yes, it does actually have solder mask up the top for the signal wire type stuff, but they're trying to increase their capacity there anyway. My hunch paid off because this here is the 240 volt terminal and there's no trace connected to there at all and there's no trace on the top ever. It goes absolutely nowhere.

So if I plug that in to 240 volts it, well. thankfully it wouldn't have blown up. it just wouldn't have done anything at all. So this board is specifically laid out for a hundred and ten volts.

Ah, bummer. So that's alright. I do have a hundred and ten volt transformer here so I can get it up and running, but you know I don't want to use that all the time if I had to use this thing. so that's a bit of a shame.

So I'm so what I'm going to do Anyway, let's continue. Shall we? this board here. Even if you didn't have the you know, the service manual configuration menu or anything like that for it, it's obvious what they're doing here now. It's got like D s and M s over here.

that could be like you know, data select. it's some sort of selection thing. They've actually got all these pads along here and this one over here. their bridge just solder bridge.

those two bit of a body thing, but you know it's not that uncommon and this one over here is on the second position there. So obviously if you had a third board over here and had an identical board you would have a third address there. And when the processor talks to the board and it tells it, okay, I want to set channel 1? It knows this is Channel 1 because that's got the address there. That's almost certainly what that has to be.

So for troubleshooting purposes, if you had to swap these two boards, then of course you'd have to change that jumper. If you want to move this one over here, just move that jumper linked over. And as it turns out, this is the digital to analog and analog to digital board has its own microprocessor on there. How do I know that without even taken out? Well, I Do have the service manual here, complete with the schematics.

I'll link it in down below and as you can see, we were right on the money with the selection line there, there's the MS thing. I've got no idea what master select or something like that, perhaps, but yet this is for selecting the different channels obviously. and we've got some serial data galvanic isolation here with on the transmit and reset lines. and if we go over here and have a look at the rest of it, Tada, it's an 8 OC 3-1 They've got their own processor on there just to handle the analog-to-digital and digital-to-analog The reason that they do that it's as an old-school design probably who dates back to the early 80s.

Got Sony Squared Prom and its own EEPROM By the way, it's not a micro controller, it's a micro processor so needs that external to 7c 256. Fantastic! Here we go. These are our arm. We've got our Dax here and this 75 28 here.

this is only a lowly 8-bit DAC So I'm presuming that might be for maybe a course or a current set resolution for example. And this duck 82 48 Here this is actually a jewel 12 bit DAC so this is used for a voltage output control. Get decent resolution with our 12 bits now. I Pull the board out here and this is rather interesting.

Look at this. We have actually got two analog devices a DAC 4248 so this is different to the schematic. so maybe they've yeah, they've upgraded it from the 8 bit tool to the 12 bit resolution from since that whatever version. service manual I've got.

You can certainly see that here. There we go look. physically smaller chip here for in 302 and there. Yeah, so they've upgraded that.

Ah, interesting. Now the interesting thing about this board is that even though got two ducks on here, you won't find any reference. I Mean you'll find some in a nice precision Op-amp so P2, hundreds and the rest. but there's no voltage reference whatsoever.

So but you go over to this other board which we saw has the we saw. This one is actually slightly different to the other two. so double sided load here which is really interesting through all on the top and a whole bunch of surface mount on the bottom. and Bingo! We're going to find another precision Op-amp but take a look down here.

Whoo-hoo there it is. Ref Oh - with a nice 10 turned trimmer in there. Now we can actually get down and see the main power supply board. That's the stuff that does all the magic.

Now this a digital 803 one microprocessor rubbage and it's got a mounting plate slash Heatsink that's effectively what it is. They've got a SIL big seal pad on the bottom like that to isolate that and they've got these look like the output power transistors here. So yeah it things going to be reasonably efficient because this thing like it's obviously a switcher. look at this huge transformer.

we got here so we're going to have some output switching. That's how you can get you know 60 watts per module into one of these if you had like a 60 watt linear supply or a hundred eighty watt linear supply total. well in a big thump and transformer and all the rest of so what? I saw as an output switching regulator I Guess the only thing I don't like is that the main output filter caps here all underneath the heatsink and that's not terrific. but we do have airflow from the fans at the back so I Don't mind the system configuration of this thing at all.

As I said, they've got this daisy chain data cable coming over here like this and this just runs in parallel between all the boards and it has different selection lines so the data is going to be the same. Obviously can't send 8-bit data bits obviously sending serial data across. it's saying, you know, please set the voltage and read back as well. So it's doing that serially and then we've got our main voltage output here and it just has another daisy chain cable and you can plug it in.

If you've only selling a single output module in this size case, you just don't populate both of these. or in this case, we've got a 60 volt option. I Believe it. I Think it might even be able to go to higher voltages.

Maybe you can not cascade to 120 volts our total by putting the three oh sorry, 90 volts a total, putting the three in series. So they're obviously putting 230 volt modules in here to give you a 60 volt output capability. wire in them in series and then they've got that just daisy chained up the top here once. As I said before, showing that wired in and hence why they've only got the single output wide in here, so it is quite configurable from a customer point of view.

You just order it and they just you know, easily make this thing to whatever requirements possible. And as I said, they put a different board over here if you want the 240 volt options on in different markets around the world. So really, it's nicely configurable. and from our point of view for buying these sorts of things on ebay, it's fantastic because we have these modular boards.

I Have no doubt that this bottom board is identical between all three. Absolutely no doubt whatsoever. these boards are identical over here. These boards are the same apart from the dress selection and things like that.

so you know we can just swap things around and hopefully get at least one of them working. And these vertical riser boards here. you know, with the surface mount stuff on it? No surprises whatsoever. These at companies like this, they're not.

you know, building a million of these things in going to Reis pin the ball because they want to change some parts or something like that. You know they're gonna and upgrade the models between. you know from previous generations and things like that, it's going to say uh yeah, let's just work in a modern you know, surface. Now boarding here, everything else completely through-hole We'll just keep that it works.

a treat. Why redo it so we'll whack in a little surface male control board and what do we got there? I Can barely read that on the screen I Think it's some Math 4000 series. see more stuff Beauty You'll notice on the backside of that board there look they've got to resist amount Lawson standoffs. and I'll show you a few more examples of that in here as well obviously a select on test resistor.

and they've got another one of those right down in there as well and also another one right up near our output there. And of course, these things are designed as I said: either select on test or some sort of like a product configuration after the fact. So this allows them to do some sort of product configuration and or trimming after they've actually had the boards manufactured. It's easy way to do it.

You just solder the posts in there and then someone can come along on their production line. Now, test cheek and then just go right. We need this model this week. Well, let's put that resistor in there.

You'll notice that this middle board here. ah, screw missing down there, Someone's how they go at this puppy. and it's interesting to note the tiny little ferrite bead around our negative sense line there, not around the positive sense line. no thank you, just around the negative.

taken the edge off something there. So there's only one thing left to do. power this thing up. I've actually disconnected these two internal boards like this, so they're not actually connected.

I'm going to bet on this channel over here being the winner considering that this one looks like it's been disturbed with in some ways. So I've got my 110 volt transformer, so let's switch this on and fingers crossed. Fan going initializing. Can't see it, but there it is.

Process is working. Beautiful. initializing. Jeez, it's taking a long time to initialize that's for sure.

Wow Come on, it's no smoke escaping. But error One one. What the dear to the manual. But actually I just cleared that.

I just and I've got my voltage and my current met in here setting here. V set 1 volt Wow I Just press my select button and it just reinitialized there. So maybe you should know we might have to reset the process so maybe it's already like it's configured for that second board and it's looking for that second board and it doesn't like it? That would be a reasonable initial guess. Anyway, not the most user-friendly thing to use of course.

Um, but yeah. I mean jeez, if you can pick it up for the 30 bucks like I did and at least get one operational channel and it's an absolute bargain. And sure enough, I Looked at the reference manual. it lists all the error messages.

Of course in that error 1 1 This is the source of the error. In this case, it comes from the output and this one is a well. it's a summation of all the error codes in decimal. but basically what that translates to is yes, it's the output channel is not responding.

So yeah, probably no wonder because I haven't plugged in that second 60 volt channel, so that's probably it. It's already hard-coded in the firmware to to be configured as this particular type of output model, so it's just not seeing the board. Bingo. So yeah, let's plug it in.

By the way, I Just noticed under this heatsink there's our current shunt. There we go. It's not a 4 terminal job, but they would be tapping that off somewhere I'm sure they've actually got three extra caps right under that heatsink in there. Jeez, they could have done a bit better than that.

I Think. And of course just before I put this back on and pair up this channel. here. you just go over visually and check for any leaking caps, any blow holes in parts, any burnt resistors or or diodes or anything else, so you know, just give it the what for.

The fuses are intact so it obviously hasn't been overloaded in any way. They look like the original ones and yep, so it should be okay to power up. All right, let's see if we get same thing initialize in. come on, you can do it.

Ah, error to one. let's find out what that one is actually I Got that wrong last time. What it is is that it to one is now now no output response from Channel two. That's what I mean.

So this before will getting no output response from channel one which was interesting because well, we have Channel 1 and now unless there's more than one error which I don't know how to look at, then yeah oh one. Okay, one is enabled so does now does one now work? Let's have a look these. Set 1 volts. Okay, so now it just comes down to a Peb CAC thing and I'm not using it correctly because it it went into standby mode and well, that is standby right? There is no power switch on this thing.

It just always runs. It's a system power supply so that's what it's doing. Enabled one and then we can very well actually Channel One select hello, No, we don't want that. There we go and we set it for one one volt.

What do we get? Tada One vault on the output. Winner Winner Chicken dinner Bloody Beauty. Okay, just a quick check of the other voltages. Let's say 5 volts.

So V Set 5 Enter Beauty 10 We don't win I 20 Whoa whoa whoa. What happened there? Holy junk wall. It doesn't like that. That's one sick puppy.

Uh-huh I Think it might be a trap for young players there. Let's go into our current output. Our current set is very low, so obviously like excess leakage at the higher voltage and that's what it's doing there. that's why it's throttling back.

So either output current protection enable you'd say well, it doesn't matter if it disabled. so let's set that I set to an amp. There we go. Excuse my hand in the way there.

There we go. So now our current output is set to an amp and our voltage. There we go. Now if we set this V Set 10 No dramas whatsoever.

Here we go: 20. it'll work now. Yeah, there we go. Trap for young players go all the way with LBJ go to 30 Beauty, we're not so I have to test it under load.

of course get out my electronic load. But yeah, I'd have little doubt it's going to work I think Channel 1. But the problem is, look, we can't select our channel 2 because we got that error message when we booted up. So that's understandable.

It's not talking to Channel 2, hence why they would get in the boards. And you know, maybe using this as a part unit or something. It looks like Channel 2 has failed in some way, shape or form. Ok, how many you saw that and were screaming at the screen because I didn't plug this in? I'm not sure if you notice that, but I just noticed that door of course Channel Bloody 2 is not going to work if and I plug in the damn data cable.

Ah, don't let's try that one more time. Shall we? Here we go? Initializing. Come on. Whoa.

look at that select. Can we select Channel 2? They'll do that. We're in like Flynn Beautiful now. select Channel 2.

Okay, well, let's get the hell out of standby. Oh no, no, it would disabled our bloody thing. Assistant Power supplies Pain in the butt? Evil? Yeah. Enabled number 2.

There we go. Ah, now we're talking B Yeah I set it to a vault and is it what? So it'll be jumpy. Yeah, it's a little bit jumpy. Oh, then maybe we've got our web do? Yep, let's try that.

Let's set that to a nap. and no, it's still a yeah, it's still a bit jumpy. Don't like that. I think we have an issue on Channel 2 there.

mmm a stability problem, but not at 10 volts. looks rock-solid at 10. and let's go all the way with LBJ Again, right up to 60. Oh, it's taken a while to ramp up.

Oh, look at the current Oh some sort of know what's going on there. Me: don't like that. so this is interesting. Now What I've done is change the current limit from one amp down 2.1 amp and it seems to be working reasonably well.

So I can pretty much set it to what anything it's A it's the output capacitance has got a discharge there. There's no load, just fair enough I guess. But although this is a two quadrant supply, so you think it would be able to sync that back down instantly. But anyway.

um yet. let's I don't know about the architecture of it as such. but yeah, I mean I was up to I was able to go up to 40 volts there before. haven't got any higher than that, but it's jumping around.

It's nice and stable. Let's go up to 50. Yeah, no worries, let's go up to 60, which is its maximum output capability. Why can't do 60? But that's alright.

Maybe there's some. you know there is some performance limit. Maybe it doesn't actually reach its claim. So although it's no load, so it should.

so it's not like it's You know, because there is like a wattage limit. So there's like a performance envelope for these power supplies where they won't deliver of course, the maximum voltage at the maximum current, for example. But anyway, it's going up to 50. and hmm.

I've got my beak. A precision electronic load setup over there. Sorry, it's not easy to get both of these in the same shot. Here and there we go.

I'm drawing point: 1 amps constant current at 30 volts. it goes over voltage on there. If I go any like. if I go up to 40 volts, it doesn't like that at all.

so it's everything's hunky-dory nice and stable. on the second channel at you know, 0.1 amps, no problems. So I've actually set 1.1 amps on there now. and I'm drawing 1 amp at 10 volts.

so 10 watts and it's nice and stable. No problems whatsoever. Yep, so I don't know what was going on before. Hmm, by the way, I forgot to show you the processor board on the bottom.

We got ourselves a Panasonic lithium battery in there. Don't know how long that puppy's been in there, but looks sort of factory original kind of. But let's uh, let's measure that's not leaking. so let's try it out.

And three Point three. No worries at all. Although you know if you're going to put this back into service if it is the original one, you know just change it as a matter of course. probably because we are talking 95 vintage board there.

So yeah, hmm, that's our version. number 27. Oh, Five Two and let's check out the processor. Aha, Well got ourselves an Intel 88 C 196 that's part of the MCS 96 family microcontrollers.

and yeah, pretty old-school Well, you know, well discontinued now. but hey, you know these were very common back in. sort of. You know, industrial controllers and automotive stuff and things like that back in the day.

So the only thing left for this apart from a cover is the spacers to hold this puppy in. Mmm I think I might know where I can find some? surely somewhere in here I've got what I'm looking for? Hmm I just have to find it. Only 330 tins. Hmm.

where's Wally? Hmm, you see him. more bloody cow feet. Never know when you might need a HT standoff rings. Bloody bet your ass.

look at those damn Andy more cow feet. That's just nuts. more cow feed. I swear I'm not doing the same one.

I'm going through him Oh Nope, nope and nope. and again, you guessed it. Nope. Wow Check it out.

I might have actually found a new packet of little miniature screws and nuts. Check it out. Wow Nice all right pivot spaces. Not what I want though, but neat.

Surely I can find the space right one out of all these. Hmm, well, he's in there somewhere. Surely think I'll call that one a win. What do you think? Awesome look at that and surely I can find my matching self Tapper in that lot.

Actually, the one on the left there might do the business. Shame. I've only got one of them. hmm and I found the three on the right.

They're the original ones on the left and well and a to shabby at all. She'll be right I didn't even have to resort to BA Janine just regular metal threaded ones instead of self tappers because well, ya got a few of those Oh black ones. Hmm Well, I'm walking back from the bunker. Score by parts.

think I got a reasonable match but it was light when I walked there and now I'm walking back. it's dark, it's raining I Score by parts. Was it worth hoarding all those parts to get these? Hmm. What's the moral of the story? I'll let you figure it out so they have it.

That's a flute P.m. at 2800 series. More specifically the 28th one - and it's quite a nice unit. Looks like I've scored a winner here for 30 bucks and need to do some more our performance testing on it.

Got to install my screws that I just got and spaces and stuff. put it all back together. Got to build a case for it if you've got any good ideas for building a case. I'm not thinking like a sheet metal folded metal case or something like that.

I'm thinking maybe a nice wooden case too for this puppy to go into. What do you think? Hmm. got any good ideas? Let me know. anyway.

I Thought that this thing would be faulty in some way. shape or form. Initial impressions: is it looks like it actually works? I'm not sure what happened to the intermittent thing on this second channel Could have been like a loose sense connection at the back or something. I'm not entirely sure I have to do some more performance testing, but it seems pretty good.

I Expected to have to swap out some of these boards and this is one of the Holy Grails of of buying stuff on eBay and repairing things like this even if you can't get the schematic. If you've got modular based ones like this, you can swap boards. You've got a known good board you can compare parts with. You don't necessarily need a schematic, even if you had a faulty board, so you know it's always expected enough to fix this.

but I didn't But even if I had to, it doesn't matter. Turns out, the schematics for this: I've only got the schematics for the top board and the processor board. That's it. Don't have the schematics for the back board here, so the analog to digital digital analog I've got the schematic for that.

Don't have the schematic for that. It's not in service manual nor the power supply, nor the actual switch mode power supply base board itself. What a bummer. So if anyone's got those schematics, oh, please link them in.

but the service menu I got moi doesn't have Am I afraid. So anyway, and these are quite a reasonable power supply if you want to have a look at these on. eBay There's a twenty eight one one going at the moment, which is the small one here. single output for like a hundred and fifty bucks.

fully working. It's like, you know, bargain if you can score one. But yeah, thirty bucks. Winner Winner chicken dinner.

And some people might be wondering, can we put binding posts on the front here just like we did for those HP slash Agilent supplies. Now this keysight rubbish. Can we do it on these? Well, there's nothing stopping you, but they don't have it. Looks like it's not a stand.

It's not an option at all on these models. Put front panel binding posts. These are system power supplies designed to be used at it. you know, bolted into racks, screw terminals at the back and you know, most likely RPC controlled via GPIB The front panel is just for kids, you know? So yeah, really? I Mean, but there's nothing stopping you.

You could, actually, you know, drill out these front panels. There's enough room behind there to actually put them in, so if you're really keen, that's a really thick front panel. Yeah, yeah, you could do it if you're you know, really can. But uh, the front panel might look a bit messy because this backer, you have to have a mount.

maybe a mounting plate on the front or or something. Heck, the plastics. Maybe even strong enough to like. If you had a metal backing plate or something like that.

you can mount the binding posts on there and then just drill a few holes in here for the wires to go through. That might work. It's doable. So that was yet another hopeful repair video.

Just popped like an ebay and Wells bloody thing works. Unbelievable. Can't copper break soaping to get something recently foamy so that we could do I repair video Honor but not know such like Murphy gets me every time it's either fully working like this or apparently fully working or it's just beyond economical repair And so anyway, we've got what we got. If you like that video, please give it a big thumbs up on YouTube because it always helps a lot.

the other direction thumb, you know what I'm talking about. You want to sky sit links down below all that sort of jazz? Catch you next time you.