TSP #93 - Teardown & Repair of a BK Precision 879B Handheld LCR Meter

In this short episode Shahriar repairs a more affordable instrument! This BK Precision LCR meter does not power up despite looking almost new. The teardown of the unit reveals several damaged components. Without any schematic and obscure part numbers some circuit configurations have to be reverse engineered. One of the main failed components is a TI DC-DC converter IC whose datahseet is examined during the repair.
The damaged components are replaced and the unit powers on normally. The performance of the instrument is verified using a HP LCR meter.
The demonstrated Soldering Iron Stand can be found here:
goo.gl/FHNJY1
The Signal Path
www.TheSignalPath.com
/ thesignalpath
www.Patreon.com/TheSignalPath

[@ToniT800]

Hi Shahriar, Are you going to make Q&M anytime soon?

[@Thesignalpath]

If there is sufficient interest in it, I would.

[@alperenalperen2458]

You've been doing more videos than usual lately. That makes me happy

[@OnTheRocks71]

Ready room Enterprise painting?! YOU MARRY THAT GIRL.

[@koffibanan3099]

I love repair videos!! Especially applied to instruments within my price range :) Thank you!!! nice painting btw!

[@ovalwingnut]

Thank you. Always TOP quality INFOtainment. You Rock 👍😁

[@ZEROSTATIC72]

Probably 2 P-Channel Enhancement mode MOSFETs connected source to source to prevent damage from incorectly installed battery and to prevent charging battery from external DC input. I would guess damage is from incorrect connection of excess voltage to external DC input. Thanks for the videos. :-)

[@DoRC]

I strongly suggest probe Master probes. They are very reasonable and are hands down the best probes I've ever used.

[@rhysd5410]

Do R/C! I second this. I was thinking during the video how much an easier time you would have with probe master probes

[@bgdwiepp]

i third this.

[@dollerstorehack]

Do R/C! fourth that. Make sure you get the alligator clips too, they're worth the ~$3.50. Furthermore they have a really low resistance which is fantastic for higher current.

[@jjoonathan7178]

I've got a pair of ProbeMaster 8017S, and they're very good -- the screw-on alligator/0.1"/lug/etc tips are brilliant -- but for poking around surface mount boards I still prefer my Pomona 6342 probes. The overall size is more civilized and sharp, springy, replaceable tips are such a joy to use.

[@bgdwiepp]

for tiny smt stuff, i actually use a pair of microtex machine needles, soldered to some 18awg silicone insulated wire and bananas and heatshrunk, they are stainless steel so they dont corrode/oxidise much, very sharp and very strong

[@babybearkill1]

valuable demonstration on repairing what would normally become high tech bin filler. Well done

[@PapasDino]

I have to admit that my workbench looks very messy when a project is being worked on but am OCD about keeping it straight otherwise...Shariar's bench looks so clean even when it's messy as demonstrated in the review teaser at the end!

[@BrookeHedrick]

Nice painting!

[@joes5669]

Great video. Thank you sir!

[@MarkMarooth]

My soldering station was so covered with unfinished work and rubbish I could not get to my irons so I grabbed my gas powered iron from my workshop. About 90 seconds later I discovered (sic) that the lens in my 3rd hand was plastic 😪. Now replaced with glass lens and a big metaphorical note to self to keep the metalwork kit in the workshop, not the lab! Nice piece of kit from Banggood!

[@DeeegerD]

BK Precision LCR meters are pretty nice. I picked up a used 878 (previous generation) a couple of years ago. Simple to calibrate as well (2 adjustments, voltage and frequency using a scope). Afterwards I purchased the DE-5000 (also very accurate) and compared the two and they were pretty much exact. You got a nice meter for $50 and a little effort. As to what cause the fault - I suspect someone tried to measure a charged cap?

[@TheSoundtec]

Super interesting , Thanks. what would you suggest as good probes?

[@braveheart9275]

Good job, thanks.

[@ChipGuy]

Wow, that is an awesome painting. These 4 transistors of which you replaced two seem to be little mosfets connected in a way that they aresome flip flop or self holding circuit. The button turns it on directly and software can turn it off. I have seen something like that done with HEF4001 (or HEF4011?) used as RS flipflop and a BUZ171 TO220 MOSFET in a meter. That circuit was from the early 90's. However, this one is neater, only 4 transistors.

[@xDevscom_EE]

Input reverse polarity protection transistors? I'd expect see more beefer transistors instead of SOT23-3's there for that purpose though. Previous owner plug batteries wrong polarity?

[@avejst]

Well done 👍😀

[@gettestudios]

Ok, where did you get the test gear shelves at? they look nice and appear to be adjustable

[@psywiped]

So much left channel audio. The video sharpness was also quite soft. How does one of the $10 kit atmel powered component testers compare?

[@ELECTROxigeno76.]

Exelent, 💯 tks

[@wither8]

"That doesnt look very healthy" haha. TSP + w2aew + Mr Carlsons Lab = why I come to youtube.

[@TheRadioShop]

Agree

[@PapasDino]

Ditto, but of course I would add "The Radio Shop" to the list! ;-)

[@PapasDino]

And MikesRadioRepair (sorry Mike!)....

[@0x637A30]

Dave is getting worse and worse year after year. Just mailbags, teardowns and useless "every day bla-bla" stuff. No repair, no useful projects, no "how to use" things. Nothing really informative. He use to have "fundamental fridays" thing, but I haven't seen it for a looooong time now. The TSP videos is somewhat "outer real life" thing from a GHz and multi-US-gran equipment universe that you'll never see in your life until you get a job in that sector of business or research. But it is at least something that is interesting. w2aew and sometimes Mr Carlson are way better and useful in a hobby "field".

[@yetanotherman4486]

Well, you should check out Marco Reps and devttys0. The first one has a great sense of humor and devttys0 is like Dave's fundamental Friday, but he shows mainly analog and HF stuff and does a great job explaining everything. He is responsible for showing me that analog and HF stuff is not that hard as I used to think.

[@SONOFAZOMBIE2025]

Great fix! BTW, what Microscope & software is that?

[@johncundiss9098]

I think the battery was installed backwards and left that way long enough for that transisitor and such to burn. It looks like the type of compartment where that could happen. A momentary backwards would be ok but if it was left in there for a long period then I belive it built heat and popped.

[@kose2ik]

16:03 This toy does not display the ESR? (at different frequencies)

[@VictorSilva-rq4kz]

what is that microscope you are using in this video?

[@reff9203]

Reverse polarity?

[@procactus9109]

I don't know the circuit, But could they be an IGBT variety ?

[@jabelsjabels]

Cool, I have one of those!

[@TheLaurentDupuis]

There is already some "Nokia Bell Labs" power banks! I hope this is the happy end of the Lucent-Alcatel nightmare.

[@ToniT800]

Yep. Nokia is also releasing few android based phones this year. I absolutely loved my Lumia 930, but damned microsoft killed it.

[@milesbancroft]

Great repair video. Now all you need is the globe fishtank.

[@3ffrige]

The box in question that you’re about to review is definitely something from Keysight. That looks like their DemStock asset tag on the corner.

[@acwrench]

they are two PMOS in series (back to bak)

[@Thesignalpath]

Yes! That is what they are.

[@jjoster]

My assumption as well.

[@ChuckCLJ]

Hi, love the videos! Could you please tell me what the yellow tape you use when using your hot air gun is called and where I might order some? Thanks!

[@stargazer7644]

Charles Johnson it is kapton tape. It has a very high melting point

[@TheRadioShop]

Battery installed backwards. Nice repair.

[@user-fk3od6dh9u]

hello What is the number of the damaged transistor?

[@mahnat]

It looks like this LCR meter has only three input terminals as the connector/slot for the kelvin probe is made of one piece of metal. So using a real Kelvin probe make no sense here as it will not be real 4-wire sensing anyway. Or Am I wrong here?

[@marco56702]

17:00 That IS Awersome!

[@SatyajitRoy2048]

These two are N and P Channel MOSFETs for soft power switching.

[@witeshade]

My dad had a Helping Hand but each arm had two joints in it, which made it super useful for holding and supporting anything you could imagine. I've wanted to find one like that forever but almost every one I've seen is like this one with only one joint on the arms. Overall it's a great video but the color temperature is definitely way too blue. I feel chilly watching the video. Besides that though, I like it!

[@MS-bc4dy]

Try the dr octopus type ones. Search realacc third hand on banggood

[@witeshade]

nice... not exactly the same as I had imagined but that does look pretty handy.

[@Bmcarroll1]

I'm a TNG fan as well. I was wondering if the more affordable LCR meters were worth it. Maybe you could talk about the differences between the affordable meters and the higher end lab spec meters. I hope Patreon doesn't discourage you from the longer videos. Thanks again

[@rkstr9965]

Just for clarification were the PMOS transistors a problem/replaced? The video just seems to jump from the transistors to the voltage converter chip.

[@matthewkriebel7342]

Rk Str you mean the one that let out the magic smoke? I'm pretty sure it was bad.

[@rkstr9965]

I guess I didn't see any comments later about replacing the component. I also thought he had trouble finding the part number off the package. So where the 2 component failures related??

[@techguy12426]

Hey Shahriar, I am persian too lol. Nice videos BTW.

[@danblankenship5744]

This damage is usually caused when a non-rechargeable 9v battery is installed and the AC adapter is used at the same time. The user manual warns against this (it's made to charge a NIMH battery).

[@AliMoeeny]

"Show me your secrets"

[@Arek_R.]

That video is soo random, first this "puzzle quesst" then out of nowhere you start talking about this DC-DC converter, then review of this magnyfying glass/holder from BG and paiting at the end, I was soo confused...

[@7head7metal7]

Looks like a spectrum analyzer to me at the end of the video, based on the large screen and single type N connector. The only one I worked with so far was a Tek unit, so this might not be a Tektronix one.

[@Thesignalpath]

It is a spectrum analyzer! But like you said, not a Tek one.

[@stanilastefan1687]

Let me try to guess. Judging on the fact that this is a battery powered device and you are keep mentioning the ac supply i would say that those 2 transistor are P-channel mosfet type arranged in a bidirectional switch configuration.

[@chevsev]

WHY WONT YOU TAKE MY MONEY lol. You have not make a long vid after I became a Patreon supporter. Edit: its a pnp npn battery disconnect so you don't pull from or back feed to the battery when AC power is connected

[@Thesignalpath]

Thank you for your generosity. Hopefully I will post my next review on Patreon. And the transistors are not PNP/NPN. ;)

[@ovi_4]

Hi, nice repair but your video lacks a great deal of really needed detail. For instance you did not say why you've changed the IC if you've found the transistors to be the problem. Also you never mentioned ( not even in the comments) what is the exact part number of the P-ch. MosFets you've decided to replace it with ? Now if my meter would have had the same defect and decided to follow your video to repair it, it wouldn't be of any use to me since I simply do not know what part number to purchase

[@Thesignalpath]

I don't think you listened to the repair carefully. The DC/DC converter was damaged as confirmed by the measurements before and after the component was replaced. The transistor is a generic PMOS.

[@ovi_4]

@@Thesignalpath Tnx for the quick reply. Yes, you are right. I must have somehow missed that part with all the ads that KZbin is pushing these days every so, often you know? Thank you once again

[@knalliebar]

hey Shahriar, about those probes. Coincidentally I replaced my even shittier probes with the ones you also bought. Why do you think these are shitty? (I do not have a reference to judge why they are good or bad)

[@Thesignalpath]

The tips were sharp but pretty soft. The insulation felt stiff. The probes consistently made poor contact.

[@knalliebar]

Agreed. The funny thing about these probes is that you see that they sell two models, I guess for the thicker ones they just grind off the smaller tip. fortunately for now... these are better than the ones I had previously. Those tips exploded when I probed 230v with the probes in the Amps socket... oops!

[@gacherumburu9958]

👍👍

[@WaltonPete]

Interesting diagnostics and repair. I see no one has yet attempted to identify the obviously faulty component and I won't spoil the surprise! My only problem with Banggood is that no matter how large my order they always break it up into lots of separate deliveries which inevitably leads to one of them going missing. Although they are quick to offer a refund I'd much rather just have the items I ordered. Perhaps if everything was shipped together it would be more reliable - it would certainly be more convenient! I live quite close to London so it's not like I live in the middle of nowhere so why do Banggood orders keep going astray? I don't get the same problem with eBay orders from China.

[@ckm-mkc]

You should buy some ProbeMaster probes. Made in USA, surprisingly cheap and probably the last probes you'll ever buy - no affiliation just a satisfied customer.... (edit - ninja'd by @do RC!)

[@yaghiyahbrenner8902]

Keysight Spectrum Analyser 17:31

[@Thesignalpath]

Yes it is! But which one? :)

[@yaghiyahbrenner8902]

Tricky... looking at those connectors on your table it's the high end one. Guessing a N9030B-RT2 the connector on the top right and Black color... clue :)

[@jjoonathan7178]

2x PMOS. I suspect MOS over BJT for efficiency reasons, and I suspect PMOS over NMOS because they're already on the + rail so fully turning on a NMOS would require a ++ rail. I feel like this reasoning is cheating since it requires zero knowledge of the circuit in question, but I suppose simplicity is a virtue as well. I made an implicit assumption that the devices were enhancement-mode on the not very good basis of never having seen depletion-mode FETs in power circuits. Does anyone here know of any?

[@sbreheny]

How did you manage to afford all of that test equipment?! I probably have about $75k sunk in mostly eBay-bought test equipment over the last 10 years but it looks like you must have spent at least $500k.

[@drkastenbrot]

its both pnp and npn to disconnect the battery completely the one on the battery anode would be pnp.

[@Thesignalpath]

Nope! ;)

[@KX36]

GaN MESFETs ;-)

[@vossiam]

When are we going to see a video with the RSA600 hiding in the last few seconds of the video?

[@Thesignalpath]

Yes, I will. It is in the pipeline. :)

[@DoRC]

Dude my gf is painting me an enterprise right now:) weird.

[@PedroDaGr8]

I would be perfectly OK if you charged for every certain number of short videos on Patreon; for example, every 4th or 5th short. These shorts are not zero time for you. Others may disagree but that's how I feel.

[@PlasmaHH]

A lot of cheap ebay probes are actually rather ok after you thorougly cleaned their surface and subjected them to some mild acid and cleaned again.

[@totaldude155]

that PXI system... drool

[@JimBob1937]

While I believe you when you say you're not getting paid for the link. I am curious why you bothered to UTM tag it for analytics acquisition tracking.

[@Thesignalpath]

The link to the product is the link provided to me by Banggood. I assume they do this to keep track of products they have sent out. It is helpful for me because it is a short URL and easy to manage in the video description. Other than that I have no idea what happens to the tracking information.

[@JimBob1937]

Ah, didn't know they provided the URL, that makes more sense.

[@TheAmmoniacal]

You should consider getting a new camera, the picture is not that clear.

[@witeshade]

ah I thought it was just me.. yeah the video quality is quite soft, even in 1080 mode. It's weird because it doesn't look out of focus, it just looks off.

[@Thesignalpath]

I did set it as one of my Patreon goals. I think I'll go and get a new camera today.

[@sykskysyk]

I highly recommend a Sony RX100 Mark IV or V or A6300 / A6500!

[@TheAlfieobanz]

....The Mantis....

[@jeanious2009]

Hey I have this meter, hopefully you approve of it...lol!

[@JGunlimited]

2 x NPN? Logic, 25% chance this is the correct guess

[@jeanious2009]

PNP and NPN transistors 06/56

[@douglasRbrown]

The oil made the video

[@KX36]

The painting is really good, but it would be better if it was TOS, not TNG.... ... let the nerd comment war commence!

[@Catstorm99]

Nice repair. Only spoilt with no guest appearance from "pooch" is it pooch? ...your furry helper.

[@Thesignalpath]

Pooch was there, but sleeping on top of one of the instruments. I am sure he will be there to bug me on the next video. :)

[@johncundiss9098]

How come Mr. bangood solder helper don't have its own batteries? Useless. Go to grandma's house and grey tape her magnifying glass to some clothes pins.

[@matthewkriebel7342]

John Cundiss so the stupid coin cells they'll use don't die when you need them most, corrode the battery compartment, and make the whole thing garbage. Also, I think a lot of hobbyists these days are using 5v USB for at least some of their projects and would have a power supply of that type handy.

[@AxelWerner]

PLEASE!!! No bangood and other cheapo adverticing. thumbs down for that.

[@SatyajitRoy2048]

Yes! it just doesn't assimilate with the quality that the videos he has been producing.

[@dgedi78]

I'm totally ok with cheapo with a good quality/price ratio...

[@dsfs17987]

are you seriously suggesting not to share some inexpensive and functional tool he found somewhere on the interwebs just because it is not made by some brand name company - industrial supplier who usually charge 5x of what that tool could/should cost? I bet most of the audience are sort of diy amateur tinkerers without the bottomless company expense account to buy tools for their home shop

[@AxelWerner]

This is sponsored content.

[@witeshade]

Ordinarily I'd agree with you, but he's not getting any kickbacks for it. And, I trust Shahriar to be honest with what he presents. Not all of us can afford super expensive gear, and we also can't afford to throw away $20 here and $35 there on useless junk, so when he says that the product is pretty good, I'm willing to believe him. Especially when he's used to top end lab gear, he's not gonna settle for some crap.