EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: mrflibble on March 08, 2014, 01:59:11 pm
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I've got a Fluke 23 here that's a wee bit wonky. As in, doesn't work properly at all. And of course no information on how it went *poof*. That would be too easy.
The behavior is roughly the same on all ranges. It looks like it just keeps integrating until it goes out of range. So when I change from Ohm to 300 mV or V==, you can see it slowly integrating towards the negative supply. Until it goes out of range and then it's just OL on the display.
The speed with which it integrates toward minus overload is different for probes shorted vs open. With probes shorted it integrates faster and goes into overload faster.
I did a visual inspection and I cannot see anything dodgy. All components look fine. Measured movs ... no shorts. Fuses are also fine. No dodgy caps (I think). But who the hell cares about components that looks fine if it doesn't work. :P
Any hints on how to troubleshoot this thing? Service manual? I am hoping that this is a well known failure mode that one of the many Fluke fans on here know how to fix. And I'm also hoping it doesn't involve replacing the Fluke 683052 asic.
Thanks in advance for any help. :)
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You can use a serie 70 service manual, they are very close.
http://www.transmille.net/ProCal/Procedure%20Library/Fluke%20Digital%20Multimeter%2073%20%5B1.10%5D/Technical%20Data/Fluke%2070%20Series%20%28PN731034%20January%201984%20Rev%201%2005-89%29%20%20Service%20Manual.pdf (http://www.transmille.net/ProCal/Procedure%20Library/Fluke%20Digital%20Multimeter%2073%20%5B1.10%5D/Technical%20Data/Fluke%2070%20Series%20%28PN731034%20January%201984%20Rev%201%2005-89%29%20%20Service%20Manual.pdf)
First, check R1 (1K), it's a fuse resistor.
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The usual suspects are all the input protection components like the fusible resistor (R1), thermistor (RT1), and varistors (RV1 and RV2).
A good IPA cleaning of the pcb doesn't hurt either after replacing any bad components.