[volt-nuts] HP419A Meter Pegged to Right
eb at telight.com
Tue Nov 11 02:43:35 EST 2014
If you're talking about washing the board only, I'd say go for it.
Just run the hottest tap water on it, and a little liquid dishwashing
detergent, and scrub it thoroughly with an old toothbrush. Then lots
of rinsing and drying - compressed air can knock out a lot water from
parts that may trap some.
If any greenish films persist you may want to pour vinegar over it,
scrub it, then repeat the above process. Just make sure that any
final washing step is with an alkaline (detergent) - not acidic - material.
If battery juice has worked into the board edge connector, you may
have to flush it out too.
At 07:28 PM 11/10/2014, you wrote:
>I'm trying to bring an HP419A back to life.
>I managed to replace the corroded nicads with two obsolete power tool 13.2v
>nicad packs. The bucking cell, I swapped for an LR50 alkaline. When fired
>up, the meter pins to the right. Randy Evans posted elsewhere the same
>problem with his 419. Perhaps this is a pattern failure due to the battery
>salts that have invaded the instrument. Anywhere these salts have worked on
>a non-noble metal, the corrosion is permanent. There was a good deal of
>salting on the main amp board connector...easily removed from the gold
>plating with an abrasive eraser. Numerous component lead to solder joint
>areas are corroded, but in no way has the corrosion worked its way to the
>point of opening connections. I can spot faint pools of salts right on the
>FR4. I would like to wash the board in water. I can plastic wrap the pots
>which are all ganged in the upper right of the board, but I'm not sure what
>a water wash would do to the composition resistors, and the electrolytics.
>Since I'm certain there must be salt all over the board that is invisible,
>mechanical removal of visible salts would be an exercise in futility.
>Any votes for a water wash? Any better ideas?
>BTW the neons are shot. That's another big unknown. My first take is to try
>and replace them. I have on order NE-2Us, and NE-83s. These are better for
>photoconductor illumination due to having more radioactive Krypton than
>NE-2Hs...Very important to fight the Dark Effect. Unfortunately, I suspect
>the original neons were probably custom manufactured for HP chopper work.
>We'll just have to see....
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