On Wednesday, May 4, 2016 at 2:59:17 PM UTC-4, Jeff Liebermann wrote:
On Wed, 4 May 2016 10:23:09 -0700 (PDT), wrote:
I removed the switch assy, the main IC socket, and the variable capacitors from the board. Several rounds of 91% IPA bathing has not cleaned the sticky electrolyte off the board, except where I could get an acid brush in to scrub. Two remaining options are to remove every other part off the board and scrub with a fiber brush or go to a more aggressive cleaner. I'm going with option two and see what happens.
John
Older electrolytic capacitors used ethylene glycol and boric acid for
electrolyte. Later versions used dimethylformamide,
dimethylacetamide, or butyrolactone. If you look these up on
Wikipedia, the table on the right includes solubility:
https://en.wikipedia.org/wiki/Ethylene_glycol
https://en.wikipedia.org/wiki/Dimethylacetamide
https://en.wikipedia.org/wiki/Dimethylformamide
https://en.wikipedia.org/wiki/Gamma-Butyrolactone
I would try detergent and water first, followed by a distilled or
deoinized water rinse. If that fails, start up the ladder of
chlorinated hydrocarbon solvents, starting with alcohol. I wouldn't
go much past trichlorethane or trichlorethylene which will probably
peel off the PCB printing, labels, and maybe the silk screening. Some
of these will also attack the epoxy that holds the PCB together. Be
careful and good luck.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
That makes a lot of sense. As I was unsoldering all the leaky caps, I never once got a whiff of low tide. When I was rebuilding Sony and Canon camcorders in the 90s most of them needed 40 or 50 smd caps, and my bench smelled like catch of the day. Clearly the formulation is different for the caps in the Flukes from what we see nowadays.
Anyway, your advice to avoid ultrasonic cleaners made way too much sense so I went ahead and soaked the board with my favorite circuit board cleaner; Fantastik. After a few soaks and rinses, the board looks, well, fantastic. It's clean as a whistle and all the goo is gone, including the crap under the inline packages and ICs. I rinsed in distilled water and now it's getting it's last IPA bath. I'll let it dry and reassemble in a few days and hope for the best.
And if that's your ground mail, I can send you two screws I have off a non-working 85 that I think needs a main chip. This meter crapped about 8 years ago and I misplaced one of the screws, but if you want the other two, they're yours. I'm on the east coast so it'll be a week.
John