Electronics > Repair

Fluke 289 not quite sorted.

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MihaiV:
.

Arhigos:
Board looks different from other nuc that i saw, but could be just a different revision. Or you could have a board from regular fluke 287 swapped inside the nuc case. The one i saw had a big resistors under resistor network and shield was different so that modified PCB can fit inside the meter.

Also, maybe i missing that, but what was the current draw when meter turns on? Also, it seems like you missing beeper for some reason. Did you just removed beeper?

MihaiV:
Hello,

Thanks for the details. Maybe only the LCD bezel with the NUC inscription is changed.

I removed the beeper to be able to apply heat from under the MXS. Being plastic, I figured it could get some damage.

The back-up capacitor had a trace of corrosion so I removed it before anything else.

F1 fuse was missing from the beginning. Only F2 was installed.

I also changed the MXS crystal, as the original one was not oscillating at all. But the boot splash screen displayed without it. I used a low capacitance probe for it. With the new one it is strong and stable.

The current draw is each phase is:
- in sleep (9V applied, meter off): 36uA;
- during boot (while green led is on): 44mA
- after boot (led off, screen gray): 15.2mA

Boot appears to be divided in two: for ~1s it draws 7mA, then for 0.5s it draws 10mA and after this the led turns on and it jumps to 44mA.
After the power on button is pressed the beeper makes a very short beep (barely audible, 10us) and the same thing just before the screen goes gray.

I must mention that the 5V rail for the analog side is not enabled, the MSP keeps the regulator disabled, so those 15mA are only for the digital side.

Arhigos:

--- Quote from: MihaiV on January 10, 2022, 04:43:09 pm ---
- after boot (led off, screen gray): 15.2mA

I must mention that the 5V rail for the analog side is not enabled, the MSP keeps the regulator disabled, so those 15mA are only for the digital side.

--- End quote ---
Yeah that sounds little bit low. It should be somewhere over 20mA.
Have you checked l1 and l2 inductors?

MihaiV:
L1 and L2 are ok, and so are all regulators. I have 1.805V at TP18, 2.950 at E35, 21.174V at E41 and 3.055 at TP32.
U17 is also OK, meaning it provides 5V for a moment, but is quickly disabled by the MSP430.
Yesterday I breadboarded and validated a IR serial link using a FTDI and I'm building it on proto-board.
I configured the link in loopback (IR led looking straight at the phototransistor) and I started the FlukeView. With a port sniffer I observed several identifications commands sent by Forms: ID, ~ID, *IDN?  with 115200 and 9600 baud.

Just to make sure, the IR receiver is CR13, the component with the dark package, right?

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