Help request for Fluke 233 with SEVERE Corrosion - Page 1
Forum section: electronics / repair

author: srmahaffy
author_rank: Contributor
timestamp: May 31, 2022, 04:25:37 pm
content: Hi Everyone,I enjoy purchasing certain non working Fluke multimeters, and repairing them as a hobby. My latest purchase is an old version, battery consuming Fluke 233.I knew it had some corrosion from a pic of the base battery compartment from the seller, and was hoping a thorough cleaning would bring it back to life, or with minimal trace or part fixes….When I opened up the base unit, it was the worst corrosion I’d ever seen!!! (The display unit looks fine).On the back side of the base PCB, (where the battery terminals are), after inspection and cleaning with white vinegar and alcohol, F102‘s pads were very corroded, but electrically is okay. R113, had a lot of corrosion, and even has a chip, but it measures okay. (10K).On the front side of the PCB, the main chip, U102 had an horrible amount of corrosion, and was so severe, that most of its leads were lifted, or the soldered ends were eaten away!!!!I spent about 16-20 hrs resoldering the leads down with painstakingly probing over and over, lead by lead to check continuity to its traces, but have 2-3 corner leads, with no traces that I can see (?).Here’s my status:1) Received meter with red LED always on even if the meter is in the OFF position (?)2) After soldering two sides of the U102 chip, I powered it up with the meter assembled, but without the top cover on, so I could probe around U102. When doing this, I used a plastic probe tool, and gently pushed down a few leads on an un resoldered side of U102 ( the side that is parallel to the top of the meter), and the red LED intermittently went out, and I could see that it had remote display communication from looking at the display, and it showed it was in resistance mode! After seeing this, this gave me hope that if I resoldered the two remaining sides of U102, maybe the meter would be more alive, without the red LED stuck on.3) after resoldering all sides of U102, I have same original problem, with red LED always on, even when the meter is set to off ;(.4) I probed some of the test points with reference to the “com” port. (see pic)Questions:1) does anyone have a schematic of this meter?? It’s so frustrating not having one!!!!!2) can anyone take the time and probe the test points on their 233 and provide that info?3) can anyone provide info on the red LED? (I know its purpose is to illuminate at higher voltages), but does it also light up momentarily at power up? Is the meter stuck in reset or something?4) how does the meter sinc with the base? (What circuit does that?)5) any advice or starting point is appreciated!!I know this meter, or base PCB may not be able to be saved, but I would like to work on more before I give up. I hate throwing in the towel.Thank you!!!Please see attached pics

author: srmahaffy
author_rank: Contributor
timestamp: May 31, 2022, 04:49:08 pm
content: Here’s some voltage test point info

author: srmahaffy
author_rank: Contributor
timestamp: June 01, 2022, 05:27:35 am
content: Hi everyone,I looked at the meter a little more and decided to throw in the towel with the traces and leads being so bad around U102. Even if I got the meter working, I would feel the integrity of the meter wouldn’t be up to par.Thank you everyone.