[volt-nuts] HP419A Meter Pegged to Right

Stan Katz stan.katz.hk at gmail.com
Mon Nov 10 22:28:21 EST 2014

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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