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| Bricked Fluke 177 |
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| AVGresponding:
--- Quote from: andyB2022 on July 17, 2022, 12:15:09 pm --- --- Quote from: AVGresponding on July 17, 2022, 10:29:23 am ---Before any of that though, can we recap on some earlier measurements? If the ADC is meant to be getting 3.3V and it's getting 5V that's not good. In the 8x series the ADC is supplied with +/- 2.5V, the REF and VIN are connected to GND. It would be useful to know which is correct for your case. --- End quote --- REF- is the only pin tied to GND. VCC pin has 5V on it (datasheet says between -0.3V to 7V) REF+ 2.5V IN+ 2.5V IN- 2.5V All display related traces come exclusively from the microcontroller, most of them are on the top layer. So the ASIC has nothing to do with dispaly (I guess). --- End quote --- I'll go out on a limb and suggest that those voltages are correct. |
| Fungus:
--- Quote from: andyB2022 on July 17, 2022, 04:11:14 pm ---I've found a great offer for around 16$ shipped to my country (Romania, Europe) for the ADC and ASIC chips. The question is, may it work with those things new? (I know meter will need recalibration). --- End quote --- It's worth a shot at that price if you have the equipment to replace them. |
| AVGresponding:
I'd be reluctant to condemn the ADC without further testing, but if you can easily afford the parts, and if as Fungus mentions you have the tools to replace them I can see no harm. A couple of things would be useful to know. 1. Could you sketch a quick drawing to show how exactly you connected it up when you tried to measure the current draw. 2. Is there a Fluke ASIC for switching the front-end ranges, like there is in the 8x series? Given your reported input impedance of 2-ish megohms, when it should be 11, I'd want to look more closely at this first. If the MSP is getting bad/no data from this ASIC it might explain why it appears functional using some of the buttons but doesn't respond to the rotary switch properly, as the front end ASIC and not the MSP is the one directly connected to the rotary switch and the range function buttons. Granted, I'm guessing a bit here, based on the 8x series design, but I think it's reasonable to suppose they'd use a generally similar system architecture, as it would save time and therefore money during the design stage. |
| andyB2022:
Here is the way I did the thing, of course first time I saw nothing on the display and decided to swap the testing leads in between them... it was too late anyway as first time I connected the GND of the battery to COM lead... As I've read here on the forum, the COM lead is very low impedance (like DSO GND) and you've gotta be really careful where you place it. Probing just with the V+ lead would be harmless (impossible to measure current without COM of course, as my intention was...) I have a hot air soldering gun, flux, solder wick... I've soldered even smaller packages, so no issues here. The only idea would be not to damage even more things while replacing the ADC and ASIC. Even if the ADC seems fine, it's worth ordering that thing too, just in case. But, I have a stupid question here, the ASIC comes already programmed, doesn't it? I know these things can do only one task... from Bitcoin mining ;D p.s. The idea of the whole topic is to try to fix those things and help other people... I could just go and buy a new meter and that's it, learn my expensive lesson, but that won't make the forum interesting, wouldn't it? |
| Fungus:
--- Quote from: andyB2022 on July 17, 2022, 06:03:23 pm ---But, I have a stupid question here, the ASIC comes already programmed, doesn't it? I know these things can do only one task... from Bitcoin mining ;D --- End quote --- ASICs aren't programmable, their functions are hard wired. It's like building a fixed-function computer out of 74-series logic chips instead of a CPU+MEMORY. They can also incorporate some analog elements in there as well. Disclaimer: I'm sure there's some ASICs out there that have a programmable section of the chip and also some FPGAs with built-in opamps and comparators. |
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