Electronics > Repair
Fluke 289 not quite sorted.
Old Don:
Purpose - if you have a can of air handy you can turn it upside down and spray the board with it. It should freeze the components and help with locating the hot chip(s). First to defrost are the hottest ones. Also, making the PCB cold can help with finding a cold solder joint. Spray sections of the PCB and turn on, when it functions every time a section is cold you've localized the problem area. A soldering iron or hot air gun to reflow should solve a bad solder joint, but not a flaky chip.
purpose:
Thank you Sir... sound advice... No air handy but just ordered some.
Yakuzza:
I’ve checked voltages and compare it to @purpose readings. Most of the readings where consisten with the “good” meter. Here are some issue I’ve found:
TP “good” mine
... ... ...
8 6.53 I couldn’t locate the TP
9 1.11 ~0
10 -2.49 I couldn’t locate the TP
11 0.46 It goes from -1mV up while measuring (I've waited until -33mV and stopped measuring)
... ... ...
The rest of the readings are very close to the “good” meter.
I managed to check with a thermal camera that there is a region with higher temperature, but the camera was really crappy so it might be a false positive. I shall check the chip name and spec and see if it makes sense to have higher temp in there. Actually higher temp was on 4 resistor and 1 capacitor on the right side of that chip (ad8617).
I guess, I can try to trace the path from TP 9 and 11 to see if it leads to anything suspicious, but without a service manual it will be like chasing a wind. Any advice anybody?
frenky:
@purpose: Is there any progress on the repair?
I have bought faulty Fluke 287 from ebay and it has very similar voltages on test points as yours.
When powered on the power led stays green for ever and on the lcd is Fluke logo. Current consumption is 42mA.
I have already removed all the MOVs and super cap. And washed it with IPA.
Next I'll check the power supply voltages on all ICs and frequencies of the oscillators.
frenky:
The only two components heating up are main IC and Q9 with markings: 1.R
Q9:
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