BK Precision LCR meter 879b with ADC failure

[ElektronikLabor]

Hello everybody,
I allways wanted an decent LCR-Meter. Now I found an faulty BK Precision 879b on eBay; Dave made an Video of it some time ago:

I did't buy it yet; it's on sale right now.

The display of this faulty device shows Err E02: the manual says that this is an ADC failure. On the internet I found out, that this accours when you try to measure capacitance of a charged cap

As an beginner I would like to ask: how big is the chance to repair this meter?
I can't find any schematics or service manual, so I can't imagine what could be wrong.

Sorry that I don't post the url of the auction. I'm afraid that could affect the final cost.

Thanks

[robrenz]

As cheap as the DE-5000 LCR meters are available now (aprox $125.00), I would seriously consider one over the BK.

[omgfire]

As cheap as the DE-5000 LCR meters are available now (aprox $125.00), I would seriously consider one over the BK.

Even lower, if you don't need USB adapter.

[mij59]

There's no information how severe the damage is, it could be a blown fuse, it could be beyond economical repair.
Even if you managed to repair it, you probably need to calibrate the meter.
 

[ElektronikLabor]

Thank You all for the replies.

As cheap as the DE-5000 LCR meters are available now (aprox $125.00), I would seriously consider one over the BK.

This one looks great!

There's no information how severe the damage is, it could be a blown fuse, it could be beyond economical repair.
Even if you managed to repair it, you probably need to calibrate the meter.

Thanks for that info.

[caall99]

Vote for the Der EE De-5000!! It's a great product, stable readings with high accuracy! Really can't be beat for the price! Been using mine to detect faulty capacitors in circuit.

[mountaindude]

For what it's worth, I have a broken BK Precision 879B, with ERR02 message showing when turned on.
BK precision web site (and their support, when I talked to them - they were were friendly and quick to respond) indicate that it could be due to a broken input protection fuse (F200 on the PCB).
No luck though, after removing the fuse and measuring it, it turns out it is just fine. Something is clearly going on.
Looking at the chips on the board, it is a bunch of 40xx series logic, as well as a set of opamps. Plus the Altera and TI 430 series micro controller.
Oh, there is also what looks like a TI comparator there, marked TY2354 http://www.ti.com/product/TLV2354/description.

So... no sign of a dedicated ADC. I would have expected one.. Or is the one in the 430 MCU good enough?

Bottom line. My unit was not an easy repair


Edit: Links to BK Precision's support site, with details on what fuse to use

https://bkprecision.desk.com/customer/portal/articles/1535400-fuse-rating-on-879b-and-878b-lcr-meter
https://bkprecision.desk.com/customer/portal/articles/1535442-getting-err-02-or-fuse-message-on-lcr-meters-878b-and-879b

[IvoS]

It just happened to me as well. What an idiot....... I was doing a motor run capacitor tests and measurements, and when I disconnected the cap from the mains voltage, I didn't realize there is a high residual charge left on capacitor. Yes, you guessed it! When I hooked the cap to my BK LCR meter, I have got ERROR E02 message instantly.
So, with nothing to lose, I opened the meter up and start poking with my multimeter. Nothing obvious at first glance. When I checked for negative voltage, I found out there is -5VDC rail missing.
I powered the unit up from my bench power supply and injected negative 5V into the marked test point. The ERROR message disappeared but still no cigar. Then I realized that I probably killed the negative voltage regulator or just simply allived it by reversed voltage, have no idea. The regulator was then producing some -1.9V or so. I was expecting to have a linear regulator there but my speedy approach without looking in the datasheed (again) didn't pay off. So, I removed the negative regulator this time, and fed the negative 5V to the test point again. Bingo! Meter works as before! Current draw is 12mA positive (from battery contacts) and 8mA on negative rail injected. I ordered the regulator from Mouser and waiting for its arrival. I hope this will fix it. I will post an update as soon as I replace the regulator. The regulator is : TPS60400DBVR
Was the unit just in overvoltage lockout? Firmware disabled? I am pretty sure if I sent it back to B&K, they would just do a magic trick to unlock it and charge me arm and leg for a repair.

[mountaindude]

Nice!
I came to about the same conclusion (that both +5V and -5V rails were toast), but haven't looked further into it. Seems I have a reason to do so now!

FWIW, the reg in my unit seems to be a TPS62110 (Adjustable, 1.5-A, 17-V Vin Step-Down Converter)

Edit: My unit has the same voltage inverter, the TPS60400DBVR.
There are also a set of TPS770xx devices used to create the lower voltage rails used by the Altera MAXII (presumably)

[mountaindude]

Finally got around to tracking down the issue with my BK 879B.
Replacing the 9V battery with a bench power supply, I noticed it pulled ca 200 mA. Woah... That's way too much for a battery powered meter like this.
All that energy has to go somewhere... and ultimately become heat.

Enter the new toy on the bench: A FLIR IR camera. Makes it trivial to find the hotspots, which turns out to be two regulators (+ and - 5V).

After removing the -5V reg/inverter, the IR image becomes quite different - the remaining +5V reg is now a lot less toasty. And when powering the meter from a bench supply, with +9V into the battery contacts, and -5V into the -5V test point on the PCB, the unit works perfectly.
Just like for @IvoS, it seems.

Now, I am waiting for the replacement regulator to arrive, should be a day or two...

[mountaindude]

...and it's a winner.

Replacing that TPS60400DBVR did the trick - meter now works as new.

[mountaindude]

Full writeup of the repair of the BK879b: https://ptarmiganlabs.com/blog/2015/12/06/fixing-a-broken-bk-precision-879b-lcr-meter/

[ATCRET]

I zapped my meter this morning causing ERR 02. Checked the fuse (good), then found Mountain dude post - thanks a lot, verified a bad -5 VDC. The meter checked good after removing the part and applying -5 VDC. Ordered TPS60400DBVR on EBay.

[mountaindude]

I zapped my meter this morning causing ERR 02. Checked the fuse (good), then found Mountain dude post - thanks a lot, verified a bad -5 VDC. The meter checked good after removing the part and applying -5 VDC. Ordered TPS60400DBVR on EBay.

Sorry about the zapping, great that you found the issue! My meter works great these days, hopefully yours will soon too.

[The Chump]

I too have had a very similar failure, causing U603 to be broken.
I coudn't get hold of TPS60400DBV but I took a chance with the closest available alternative, ADM8828
Just requires blobbing the SHDN pin to GND and it works