Products > Test Equipment
Repairing Fluke 8845A/8846A Multimeters - Part identification
floobydust:
Using the entire SMD marking code- it does not search well. Finding the root marking code, by removing a possible data code/manufacturing plant number etc. helps a lot.
Another aspect that can help is a search query including the package name.
It's mostly experience that tells me what type of part it could be, based on the circuit sections I can estimate.
Orting:
Okay, humor me here! I’m a hardheaded 67 year old medical retiree. Learned electronics in the Navy way too many moons ago! I’ve repaired and built amps for musicians for years and still work on things that I buy dead and repair them, however, trying to repair these DMMs is a royal pain! I just don’t have your experience, wish I did at this point.
I didn’t ask about U2, but upon looking closely, the nomenclature looks like uA 6. The number 6 is at 90 degrees to the uA. The u is the Manufacturer correct, but seem to remember seeing uA as a manufacturers code. The only thing left is the 6, so how do I find a part with that?
Dazed and confused!!!
floobydust:
This is supposed to be fun, 3-10x magnifier and bright light included ;)
People here will help out.
SMT markings use the alphabet/numbers (not Greek) so U3 is possibly "HA" or "MA". It's a SOT-23-6 package. Not important right now, it seems to be part of the isolator circuit. I don't know this model Fluke really well but worthy of a repair. When I'm more awake I can look for the IC and let you know what steps I took.
You don't need to know all the parts until you find something wrong and need to trace up or down stream.
For now I would carefully (don't slip and short something out) on DCV measure the voltages on Q5 with needle probes. If you can't fit a probe there, then use nearby traces to other parts, or the vias etc. as a place to poke.
TP5 looks like DGND, a place top keep the -ve probe of your working multimeter.
AVGresponding:
Definitely HA. Worth noting also that the solder on that probable pass transistor looks like it might have seen some unscheduled heating
Kean:
On U3 (which I think you meant rather than U2), I read it as HA or MA, followed by rotated 6, and a SOT-23-6 package. A better photo might help to confirm the first letter.
One website that can help for looking up SMD part codes is https://smd.yooneed.one/ - you start with the first two characters and then filter by package type.
Except for diodes and transistors, I've found it rarely gets you direct to the part - there is just too many options and many manufacturers use shorter codes so they can include batch info. You often need to analyse the circuit and pin connections, as well as surrounding components, to narrow down what type of device it might be. Then start looking at datasheets of potential candidates and hope the datasheet actually mentions the SMD markings. In several cases I've seen the marking information get lost in newer datasheet revisions.
Note that sometimes it isn't the first two characters that are significant, as manufacturers may use the leading characters to indicate batch or manufacturing location. More an more manufacturers do seem to be rotating these characters to help differentiate them (like the 6 on U3). Sometimes they will underline (or overline) certain characters - but you need to look at the datasheet, or the specific manufacturer part marking standards to understand what they denote. On these small parts, there is generally no indication of manufacturer, although sometime you do recognise a marking standard.
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