Hi time for a repair video. It's the Classic Fluke 23 multimeter, which is sort of like the in more industrial version of the Fluke 70 meter. Anyway, it's up. It's yellow instead of uh, you know, the charcoal type color of the Classic Fluke 70 series and I don't know where I got this from.

I found it in the bottom of my multimeter box. Everyone's got just like a box of multimeters, don't they? In fact, I have several box of meters. In fact, one of them. Hang on.

Hang on. One of them's just over here like this. Um yeah, there's just a this is one that I've got here in the lab and there's another one in the bunker which is where I got this one from. So anyway, um yeah it.

um I well I just whacked it. One of the little rubber feet just came off by the looks of it. Anyway, uh yeah, uh, bugger, that's ruined now. All the electrons are going to fall out the serial number for those playing along at home.

Made in the United States of America of course. and these are still very good meters. And as you can see, um, it actually works. I'm feeding in 30 milliamps from my uh, programmable Dc source and you know that's good enough for Australia 29.95 No worries.

But unfortunately, um, that's as good as you get. Trust me, there's a compliance voltage coming out of there and it's just reading zero. So yeah, that's gone. Ski.

Um, same with the 300 millivolt range and the Ohms anything will probably work on me. Yeah, it just decided to oh no, no, no, there we go. No, it's not a happy camper. Yeah, it was doing.

That's what it was doing before, just without any leads. So if I, oh yeah, yeah, there we go. it was doing that. So that's one sick puppy.

So obviously the main chipset works. the measurement actually works. But what? What's going on here? The bar graph is just going schizo and look, the Lcd looks like it's got, um, I don't know whether or not that's in the Lcd itself. It doesn't look like, uh, your regular type of Lcd damage.

Anyway, we'll get in there and it's now showing negative mega ohms. So yeah, it's one sick puppy, but does work on milliamps, so that's interesting. Let's crack it open anyway. as cracker open.

Yeah, it certainly does seem to be inside the Lcd, but the contrast is still really excellent on it, so it works. so it's not a problem. But the good thing about these old flukes is that you can buy replacement Lcds for them on ebay, so I don't know if they're genuine fluke ones or somebody's done like, third party ones or whatever. but a bloody foot came off again.

Anyway, there's the bottom of the case for those playing along at home and the, uh, switching. Um, all the you know, the plastic indent stuff. It's in there. so I'm going to actually switch that off before I get in the wrong switch position.

and um, there we go. We're in. so let me take the battery out and let's have a squiz. Now from memory, this jumper here.

That's the one. Um, you can actually change. This works. I don't know about the 20 series, but certainly for the 70 series.

If you've got a fluke 75. if you just change the jump link over, you get the function. You get the touch hold functionality of the Fluke 77, but this one already has touch hold so I'm not sure what the. Not sure if that's the same deal or what not.

But anyway, um yeah, is that our sampling cap up there? I can't remember. Anyway, that is the classic 70 Uh series. Pcb never really understood why that uh, cutout was there. It was always a bit weird.

but anyway, um yeah. the amps, uh, 10 amp range doesn't work because there's no fuse in there. Um yeah, this is all you remember. This is all pre, uh, you know, modern cat standards and stuff like that.

So I don't know if the original uh fluke would have had a uh, ceramic, uh job in there for the milliamp uh range if you know, let us know. But anyway, um, nothing obviously blows a tag tent down there. Oh, there's pesky tag tantalums, another one in there. Um yeah.

never trust tag tents. uh, especially in something this old. But anyway, there's our 10 amp current shot. Anyway, nothing obviously blowing on the front end there, but whip the board out and have a squeeze.

We've got our shielding on the bottom and then the oh, oh, hang on. what the what the heck? that was just sitting on the bottom? No, right that would have come from there. Okay, that's to connect. Jeez, that's it's all a bit, how you.

Oh, there we go. Oh, got some corrosion up there. that's not a happy camper. Yeah, it looks like the battery is leaked, so I'd be checking.

As a matter of course, I'd be checking that trace continuity of that trace around there just to make sure that is still good and hasn't been corroded away in there. Um, because that's a that's a distinct possibility. But apart from that, um, nothing serious. All the, uh, front-end banana jacks are still.

um, the solder condition is still good on those. they're not cracked and everything else looks pretty hunky-dory And of course that's the uh, the custom fluke. Uh, front end chipset. That was back when they did it all in house.

But let's let's get the cover off. Self tappers. Fluke. Were fond of the old self tappers.

There you go. That's our little, um, shield over there. This certainly looks and feels like plastic, but I reckon that sucker got to be conductive. Yep, there you go.

There's our hybrid divider down there and it doesn't look like much on that side. but I think if we flat flip that over, it doesn't look like much either. But if we get that in the right light, should be able to see all the patterns on there and they'd all be laser trimmed. That's the idea of these uh, ceramics? Is that? um, these hybrid ceramic resistor dividers? Is that you can actually, uh, laser trim them without any worries? And yeah, then coat the sucker and bob's your uncle.

That's why these things are still accurate 30 40 years later, and because of the voltage reference as well. Mlm385 is that a 1.2 volt jobby? and that's the Uh standard part that's under uh 30 ppm drift. but I don't know if there's any other grades or anything like that or what, uh, what fluke do to them. So we can also get the Uh Lcd out of there as well.

But anyway, um, yeah, I'm going to measure a few things around the input, but uh, first of all, I think we'll get a schematic. I do believe that's uh, the 32nd week 89. So yeah, we're talking about uh, 31 years or more. Wow, let's have a look under the tagano here and the uh, wafer switch down here.

This all looks in really good nick. Check that out so I don't think there's any any worries down there. The rain switch is one of the things that you want to, uh, suspect in an old needle like this. that.

uh, as I said, yeah, there doesn't seem to be any any visual damage at all there. Sort of tried to clean up that a bit. Um, anyway. I did want to measure that trace, but it actually once I've cleaned it up, it does actually looking good.

Nick, let's sew in. Yep, we're in. buzzer. Hopefully that comes on the audio.

Um, and it's got a visual alert too. There you go. Um, so let's go from there. Yep, no workers.

That's fine. So that track hasn't been in a way. The one? yeah, if that hasn't been eaten away, then the one below it's not a problem. Yeah, it's all good.

After a visual and that, um, we are going to go to the videotape to the schematic. so let's do that. Now this is the Uh service manual for the Um Series 2 model. This is the original one and because Series 2 will have Series 2 written on it, I believe.

Anyway, um, and this is, as I said, covers the 73, the 75, the 77, and the 23, and the 21.. I believe this is the same because if you have a look at the board here, trust me, I've had a good look at this. This is the overlay and it looks absolutely identical. As far as physical components and everything, it it looks fine.

So we're going to run with this. Like I said, here's your divider resistors here. That's that. uh, ceramic hybrid jobby.

That's uh, that does all the precision here. and your voltage reference there. it is down the bottom there. no workers, so that's all fine.

So the voltage reference is fine, because this thing works. But as I said it, it only seems to work in current mode. Okay, so we've tested the milliamp here, so that works, right? So that path there and that bypasses, of course, the ceramic, uh, resistor divider and the other input protection stuff up here. Yeah, and that just like goes into the converter and whatnot.

So all that sort of stuff, right? So all this all this should be working. We, we know, that's all working. The problem is is that our Dc path over here certainly doesn't work. and now Ohms is doing something really oddball.

Anyway, we've got a spark gap there, which they call E1. It's a 1500 volt spark gap and you can, physically, um, see that over here. You physically see the split in it. There it is.

It's a one, one to two kilovolt. Or is it one point to get? No, it's one to two kilovolts. So one point, fifteen hundred kilovolts. Um, average.

So um, just as a matter of course, like I'm going to measure that one Meg resistor. but it's like it's unlikely that you would get, like, say, say the one Meg was just open for some reason, right? It's you know, it's blowing. Whatever. So we've got an input here for the uh volts and uh, millivolts range.

We've got uh, mod protection down here like this. Um, Rb1 and Rv2. Yeah, here's where the schematic differs. because.

uh. this one shows Rv1 and Rv2. It shows two mobs there. But uh, yeah, we don't have those.

So that's interesting. We've got a 1k fusible resistor here. There's our input. Okay, so it goes to both of those.

There are two different paths there. There's your one Meg. Okay, so that's your owns path, right? So here's our two paths, right? So this is the upper. So this one Meg is, uh, the upper part.

This is the Ohms. Okay, so that's the one Meg input. Um, and then this one is. our fusible is our 1k fusible thing here.

but the 1k fusible on the other side of that. It shows that there's two two mobs there. Okay, Oh, okay. it goes.

Goes back down here. It's got a spark gap. and there's the other series. Okay, it's got one mob and a spark gap.

Okay, rather than two mobs. Okay, there you go That That explains yes, because that one, that spark gap goes back down here. Okay, that's yeah. Yep, it's different.

Okay, got it. So we don't have a precise match, but it's going to be good enough for Australia, Trust me. Uh, we need to go into I guys goofed this up on the video the other day. We'll go into Ohms mode and that's our one Meg input.

And yep, it is One Meg. No workers. Okay, and this was 1k. Fusible.

Is that blown? Haha. There you go. That was too easy. So that is a white that's green and blue like that? I I don't know.

Anyway, that's supposed to be a we could like. You don't have to put a fusible resistor in there, just place it with like a large carbon 1k uh resistor in there would be absolutely, uh fine. Our spa gaps open and uh yeah, just want to check our mob there. Our mob is open whether or not they're still functional.

Of course you would have to, um, overload, test those to find out, but don't you know? there's no visual damage? So okay, so that's definitely why our Volts doesn't work. so I would be tempted to fix that first. Aha. that being open would actually explain the Ohms as well.

because it's Volts, millivolts, and Ohms, because you've got to have source and read back as well. And um, and of course this up here is for the Ohms range. but we know that one meg is fine, so it could be. The only thing blowing is that 1k input resistor there? Wow, that would be nice and of course you know.

Look, we've got our Um. transistor clamp. uh, down here. our transistors clamp.

I've done a video on that. I'll have to link it in on how that actually uh, works. Did a whiteboard uh thing as part of my 1000th video. I think that was clamps work.

Don't know whether or not it was invented by Fluke, but fluke have been using it since the 70s. So anyway, and all multimeters to this day. well, a lot of them. Um, use the transistor clamp method like this.

Anyway, it's very interesting. You know, if if something like this was blowing like, then, well, you know your chip's going to be blowing. Anyway, yeah, I'm just going to replace that resistor with a 1k uh, hopefully I've got a big enough uh, carbon 1k resistor and I'll whack that in there. and um, see if she works Because as I said, the main adc and everything seems to be working the reference because the current works so could be as simple as that.

But uh, let's work that out. I don't have a 1k, um, in a suitable Ah size. Ernie Bernie Uh, so I'm just going to whack in a little quarter watt jobby and uh, just to see if it works and then after that, like maybe I can. Like, you know, salvage one because 1k is pretty standard for an input surge resistor in input protection resistor on Um meters.

So you know I can, maybe, uh, just salvage one from somewhere and to be fit the age of this thing, I'm going to use one of my original stock 1k. Look at the rust on those. Look at the corrosion on those legs. Ah, no workers.

We can fix that. Just get a scalpel and uh, and just give her a scrape. rotate around and uh yeah, that'll be good enough for Australia. Actually, I think this resistor could actually be older than this meter because I have actually got I've still got.

I'm showing in a video somewhere. I've got my original component cabinet um, of my original stock of pass that I had as a kid or some of them. So yeah. so there you go.

That's been how you doing and clean that up later. so we'll just whack that in there. I know that's that. that is that is terrible, right? That is so wimpy.

I'll just lead at least some lead length on that. But I don't care. I don't care. I just want to see if this fixes the problem because it would explain both voltage and Ohms mode.

Uh right. Oh sorry, you didn't see that off screen professional engineering video blogger. All right. I'm going to whack that back together.

See what's what? We don't win. A chicken dinner feeding in 300 millivolts that's in the vault range? Try the millivolt range. Oh look at that. Look at that.

Oh bang on. Bang on After 30. What? Over 31 years or something so common for flukes like this. Anyway, does the Ohms range work? I haven't? The case is still a bit springy.

Look at that beautiful go boom look at that boom shaker Boom My whackers? let me get my uh. precision resistor out. Uh, wrong, wrong polarity. Oh, look at that.

Look at that 1k bang on after 30 years? That was it. So it's yep. there we go. Look at that.

Look at that. look at that bang on to the least significant digit. that's fixed. That is a winner winner chicken dinner.

I'm sure the 10 amps will work if I actually whack a 10 amp working 10 amp fuse in there. I'm absolute. I have absolute confidence in that. So um, there you go.

It needs a good cleanup. I might give it a clean. Um, so yeah. get some isopropyl on there.

And oh yeah, check out the side. It's just yeah. of course. So it used to have the holster.

That is the shape of the holster so you can see how it's discolored like this, Is this due to like Uv over the years? Or is that, uh, will that clean up with isopropyl? Yeah, I know. I won't leave that resistor in there. I'll try and source a better. It's not like I don't have a lot of scrap meters.

So yeah, I can just get an input surge rated resistor Um, Carbon joby from somewhere. No workers, a bit more elbow grease. I might be able to get the Uh 36 off there. This discoloration around here? I think that's permanent.

You might have to treat that, um, chemically somehow. I don't know. But the, um, these two screws here are stripped. I've lost another foot.

it's somewhere in the lab. I don't think I'll get those back. Um, might just take them off permanently. And of course the uh trick with not threading the self tappers on um, fluke meters.

When you go to screw it in, what you do is you just rotate counter clockwise until you hear it drop into blend here and feel it drop into place and then screw it in. So it uses the existing thread on there rather than cut a new thread because if you cut a new thread um, x amount of times, it's just going to. yeah, the whole plastic stud in there is going to strip. You can see that these up here.

I can just push that straight in there. it's it's completely stripped. So yeah, somebody hasn't uh yet used the existing thread when they change this. Although that you know, these things have got like 2 000 hours battery life to change the uh, you know, the 9 volt uh battery in there very often.

But anyway, so yeah to fix that, either I don't use a bigger screw or I don't know, bog it up somehow. Maybe. And just for completeness, I'll take the Lcd off and up. Yep, there's our zebra strip.

Our elastomeric connector like that. top and bottom made in the Usa. None of that gold plating rubbish either. That's just that's just good old tin plate.

Yeah, good on you fluke. Unbelievable. Anyway, yeah, there we go. Fluke branded as well.

Oh yeah, that just clips off. Yeah, it's gonna be nothing we can do about it. that's inside. Oh, this still still stuck.

Ah, there you go. There's the part number for those playing along at home. Yeah, that's just. uh.

that's one sick puppy if you want to fix that new Lcd. But as I said, you can buy them. Let me go look up the price. Actually, I can't find the 77 Lcd on ebay.

Um, I can get like the 79 and 29 series 2, but um, I believe that's different. I did find a 77, but that's a series four. Um, yeah, I thought they were more readily available than that. But in any case, like some were, you know, like 40 50 bucks something like that and it's certainly not worth that unless it was dead.

Given that it works, I'm yeah, not gonna worry about it. I'm just gonna leave it as is. So anyway, there you have it. There is a repaired uh fluke, 23 multimeter.

Uh, and the Lcd doesn't really bother me that much. Kind of adds to the like the character. It's got a bit of street cred this one. Um, so yeah, that's is that a common fault in these meters? I don't know.

There's a lot of people out there who do, uh, buy like second-hand flukes on ebay and uh, repair them. Wouldn't surprise me if that's a common fault, but I don't know, um, offhand if that input, uh, resistor is like commonly failed. Well, it is fusible so um, yeah, I guess it did its job. It fused, does that like.

so if you get an overload on there, that's his job. It just goes open. so you know, like I wouldn't bother like putting another fusible uh one in unless you're you know, unless you're that really keen. I think just a regular 1k input protection resistor from, you know, scrap from another multimeter or something, or even just you know, a big like to what jobby or whatever it is, Um, that'd work just fine.

So because if you want the utmost in uh, you know, cat rating and safety and everything else, you'd be buying like a proper modern uh one designed to meet the standards and whatnot. But anyway, still a very nice, very useful meter. The Fluke 70 series, hands up. In the comments, If you still use your original 70 series, who's got you know, like did you get like a first batcher or something like that and they almost always still work and they almost always are still within spec and you saw it here.

Bang on. Except for like the current ranges which were just a couple of digits off. but that's like well, within spec. So yeah, no worries whatsoever.

And yeah yeah, the touch hold the button works. Um yeah, that's it. Just the fusible resistor did its job. That was too easy, wasn't it? should have been a like two minute video.

but you know this is the Ev blog. Catch you next time you.