DR #12 - Fluke 8050A Multimeter Troubleshooting and Repair

everyone its Nick welcome back to another duality repair video I recently bought this lot of six fluke 8050 a bench top digital multimeters and I already plugged them all in I tried to turn them all on and really none of them display anything except for the bottom one the display was a little messed up anyway so we'll see if I can take all six of these and make at least one good one maybe a couple I don't have a bench top multimeter so it'd be good to have one out of this most of these are in fair to poor condition cosmetically I'm not worried about adhesive or anything like that I can remove that stickers but anything cracked like this one you can see the front bezels cracked I'm gonna say that one's gone cosmetically anyway it's a few others that have some chips and scrapes but there are a few that are in pretty good shape so I'm gonna try and make one at least one good one maybe two or three out of these so let's zoom in on one of them and take a look at the front panel here's a closer look at the front panel of one of the units they're all pretty much identical other than three of them have a little battery charge status LED right here this one doesn't have it they are all the same model at least that's what their designation shows in the front panel so I'm not sure what that battery charge why that's on some of them not the others I'm sure we'll figure that out as I open them all up but fairly simple on the front you know this little LCD display this is gonna be a concern as these can can wear over time and some of them might be broken or damaged and then you just have it's all push-button right so you have power on/off button you know this relative on/off button I'm not sure exactly what that does I assume measuring voltage relative to something else I look in the manual to see exactly what that is on the Left we have a capability of measuring AC and DC waveforms right or voltages and then here's where you select your your measurements here they're gonna measure volts milliamps or resistance in ohms and then here's where you can these all these selectors show the different scales within those measurements so within volts we have 200 millivolts 2 millivolts 20 millivolts excuse me 2 volts 20 volts 200 volts and it looks like we go all the way up to a thousand volts TC so that's nice and then in the milliamp range we can go down from 20 micro amps 200 micro amps since it's nice all the way up to 2,000 milliamps which is 2 amps so that's not bad and the resistance we start off in the 200 ohm range and we can go all the way up to 20 mega ohms also very nice so I get at least one of these work and would be a nice handy little bench top multimeter to coincide with the standard multimeter that I have so I think I'll just start with this one there's no reason why I shouldn't start with this one over or any other so I'll open this one up we'll take a look inside before I open it I suppose I should show you it looks like when I powered on we at least do have a display but it's definitely not correct first of all something is drifting and let's see what happens if I change modes here so I'm in the Volt mode mode K ohm mode no one changed what the display looks to be a little wacky so hopefully that can be resolved but if not I'm sure at least one of these others will have a good display so anyway as a reference that's what this display is doing the one that I'm gonna open next ok here's the unit removed from the case disassembly couldn't have been easier there was one screw on the back and the whole thing just slides right out very easy did a very small amount of work already so obviously this is not how it is laid out internally this display board here sitting on top just screwed in so I unscrew it and fold it over just so we can get easy access no that's it's pretty simple there's not much going on in here obviously there's two boards we have our power board over here on the left and then our LCD display board on the right pretty simple and since we're having display problems let's just dive right in schematics there's only two pages for schematics this one has the power as well as the display up here and so we know we have power for sure because we do show something on the display we're having issues with the display so let's zoom in on the display here it's laid out exactly how it is on the actual display so we have looks like we have a this BT which i think is a battery and then you have plus here and then you have your four seven segment displays and then you have some other DB HV and relative there and so I assume when you powered on these should all be you know close to zero or something they should all be reading then obviously but I think we were missing number three and we were missing part of two something like that so obviously each of these seven segment displays is controlled by an individual IC and the one we were most concerned with was I believe the second one second or third so that's going to be you thirteen or you fourteen so if we look at those they're all laid out identically pins nine through sixteen excuse me fifteen control the output with the reference to pin 16 which was ground so let's take a look at a good a functioning seven segment display which I believe was this last one here and we'll check the outputs relative to ground and we'll compare them to our bad one which was two or three and see what we're getting so let me plug it in and power it on all right powered up yeah might as well just look at the display yeah and it's upside down right now remember that so this is actually the farthest right and I can see know if you can see that see when I put pressure on it the display changes so that tells me it may be a connection issue somewhere let's just take a look so again we know that the furthest right is working again this is upside down and it's the third one that's not working well at all shows nothing and that one is here which is gonna be you that's tough to read twelve thirteen fourteen fourteen so that's gonna be right here so let's use one of these others for reference maybe this one put my meter here and we should have some sort of small DC voltage nice I can slide this up oh yeah okay again let's test a functioning one for reference and we have pin sixteen let me see pin six teams up here this one we know is working so sixteen to this pin negative two and a half next pin negative two and a half two and a half okay so to display one of the seven segments we need approximately negative two and a half volts so let's take a look at our problem right here you fourteen let's do the same thing ground probe on the ground and negative two and a half I'm just going to skip a few negative two and a half negative two and a half okay so this is outputting the proper voltage to our LCD display but for some reason it's not working as I said since I can apply a little pressure and that changes the reading the readout I think it's gonna be a connection issue so I'm gonna power it off I'm gonna see if I can disconnect this somehow from the board I'm not sure if it's soldered in or what and we'll take a closer look to see if there's anything wrong there so I was able to remove the ribbon cable really easily I've never seen a mounting like this but uh basically it's just kind of pressed into place against the board here and so you press it into place it seats around there's these holes on the edge of the cable here and they seat around these mounting post and then they push up flush against the board here and then you just press this strip down onto it tighten it down and it makes contacts that's interesting so I way to do was disconnect this so now we have the board the board separated and I noticed that so I took these two screws out and it looks like I will be able to unmount this and you zoom in on here I already see something so that's not a black hair that's a crack here so I wonder what it's gonna look like when I take it apart let's take a look and see how not sure how hard it's gonna be I don't think it's gonna be too hard tools start with the flat head it looks like it's clipped into place on top here and of course it was screwed on the bottom but it's still rigid so I'm gonna try and separate it here sure the plastics hold and brittle by now which is probably why it cracked on that outside there so I'm gonna try and be careful there we go okay that does pop out and let's see what happens there we go okay there's our screen and it just slides right out there we go let's take a look all right so here's a strip that was on the screen here and this must be what's interfacing between the board and the LCD let's take a closer look at that it's still a little strip it it's kind of it's very flexible it's kind of rubber rubberized but you can see the little striations in there and they happen to be the same width as the width of the solder pads on the board as well as the strips on the LCD so I don't know if you can see that let's see what's gonna help you see it yeah you can see those little striations on this side here that's what's making contact with this strip which is making contact down here with the board so let's see how that oh yeah there we go look at that see that that's pretty obvious so we have a crack right here see if this comes yeah comes right out so this is our mounting block this sit oh my gosh no bad it is on the bottom this sits into the board our LCD sits flush against here and this kind of sandwich is the LCD to this and really your little strip is going to lay right in this little seam here and the downward force is gonna push down and force the strip against the board and should also force the LCD against the board like that so there you go so your strips gonna sit right here in this little seam and then it's gonna press on the bottom it's gonna make contact with the bottom of the LCD and I bet ya that you're just not getting solid contact due to this crack there's no way and that's probably why our third one is making no contact cuz it's cracked right there terribly it's really just cracked all the way around so it's in rough shape I bet that's our LCD problem right there so I have five other ones the odds that all five of the other ones of these are correct as well or I would say low so I'm hoping I can pull one off of the other and install that so I'll go try and find a good one from another unit you know be back got pretty lucky the first one I checked no cracks so I'm gonna throw this new one in it's not new but intact I have the strip in there I think it's aligned throw the screen in there and see all right it's installed we put the ribbon cable back on I'll show you how this kind of worked kind of interesting again you see the holes on the side of ribbon cable here it's fit right inside these little studs here and once you get them in you can slide the lay this over it and on the back I want to drop the screws it's got this soft little pad to push on the top of the ribbon cable put that on tighten her down I think so wait let's plug it in see if that helped all right I'm gonna try us here we go again we're upside down hopefully we get some something different yeah oh so close then we'll save it that last one there I don't know what that is I'm not sure what that's about it's not quite right either see I got it to go there again that's just the connection issue anyway we're about there maybe that's it see yeah I got it let me push some buttons here see what we can get mmm okay so that's where am i out here that's resistance and let me change the scale see if that changes anything yeah should change the position of the decimal point yeah seems to be working let's try what's next current now let's change the scale here hmm seems to be working I'm not sure what that looks like the division symbol want to see what that is let's go to volts volts let's see oh I see that's just positive it's supposed to be the positive versus negative yeah that's looking really good but one thing I'm gonna do before I put it all back together I'm gonna check some voltages here because I imagine a any any of these electrolytic SAR really old and they need to be replaced and they're gonna be filtering our power rails and and then be our regulators here they're old as well six volt negative five volt these regulators might be uh you know getting old and as well so let's see some test points here for voltages test point two isn't positive thirteen test point three is positive six test point four is minus five test point five is minus 10 so that should be easy enough to locate and test those and if any of those are off try and get those corrected but just play is still working it looks good so I'll check those will choose next okay I checked all the voltages everything checked out just fine no concerns there so I put everything back together put it back in the case clean everything up really well got all the stickers off I was able to clean the front faceplate up really nicely including the buttons so everything looks really nice and it's time to test it out so I have it hooked up to my HPE 36:12 a power supply that is from cleared so we'll start off by checking voltages powered on supply and we're in the we'll start off to the low lowest range and it can go really two volts it's got the two hundred millivolts but I don't supply isn't really capable of that kind of resolution I guess we can try it out so we'll be in the 200 millivolt range and it's already reading you know so many 5 millivolts so if I increase that yeah so we'll keep in the 2 volt range and I'll put it at 1 volt on the supply see what we're reading on there okay one volt on the supply 1.08 four on the multimeter very good let's jump up ranges here and we'll go to ten volts ten on the supply nine point nine eight two on the multimeter very nice let's go up the next range and we'll go 250 volts 50 M supply 49.7 9 I'm a multimeter I'm ok with that and we'll keep it in 200 and we'll go up to 100 volts on the supply this supply can go up to 120 really 130 but uh going up to a hundred is about as good as it'll get so it's 200 volts on the supply see what we get on the meter 100 point zero on the supply ninety nine point six on the multimeter I'm pretty happy with that so first of all my supply isn't calibrated and then of course I haven't calibrated this so for them to be that close all the way up the range from really 1 volt 200 volts I'm pretty happy so next let's do we'll do resistance and for that I'll just get a few resistors I guess I have a some 8 ohm power resistors I suppose I can Maya for those I can do one and then connect them in series to get up to 32 ohms so that'd be good so we'll start with that ok so I have it hooked up to my 8 ohm power resistor obviously that's looking pretty good at 8 ohms put one of those in series just to get 16 ohms and we'll see how that looks and here we go should be about sixteen sixteen point one three that looks good okay and I'll have to dig up some resistors to to check the higher ranges so let me get some of those and I'll be back alright I have a five point 1k resistor hooked up and I'm now on the 20k range and you can see it's reading pretty well four point nine five let's see I have a 10k resistor here we try one of those stay in this 20k range nine point nine seven K good all right I'll have to find some more to bump it up to the 200k range okay resistors all right here's a 47 K see how that looks yeah forty seven point three looking good and I'm not sure I can go much higher I don't have many higher value resistors to go into 200k range wants to stop there so we'll just jump ahead to current alright I have my meter in series with the output of my power supply and my power supply is limited to 50 milliamps or 500 milliamps excuse me so that's a as high as we can test it so I'm in the 200 million range on my meter and so go ahead and crank up the voltage to draw some current and I'm going through my 8 ohm 50 watt power resistor so here's my voltage output on my supply my current current output on my supply and then of course the current reading on my meter so let's turn it up to 100 milliamps on my supply and see what we get 103 on the supply 100 and 506 on the meter pretty good keep going here let's go to 200 and okay of course kind of change scales there so 201 on the supply 207 on the meter it's still not bad yeah let's keep going let's just go to 450 so 451 on the supply 467 on the meter so you know good 15 milliamps off I'm still happy with that again I can calibrate this later but everything at least is reading very close again the supply isn't calibrated itself so who knows which one is closer to accurate they can both be off so anyway this guy is fixed pretty happy with that I was able to clean up really well so this is uh this is gonna stay on my bench and I'll be able to use this in the future and I'm going to take a look at the next five of these multimeters and see if there's one that's feasible for fixing if there is there'll be a part two to this video if not I'll probably just have a bunch of scrap laying around for that so either way thanks for watching I appreciate it subscribe if you haven't subscribed and we'll see you next time thanks you