[R-390] Removing 390 non-a varnish

[Dan Merz]

Hi again,  looking around a bit in the archives,  I suppose this varnish is
the MFP stuff.  Was this used on all 390 non-a's?  Evidently some types
contain mercury with some potential hazard if overly consumed or inhaled.
I'm not worried yet !! None on the switch solder joints so I guess they
sprayed it before assembling the switches so the contacts wouldn't be coated
- clever fellows that they were.  Anyway,  I gathered that this stuff is
probably best just flaked off where heavy deposits lie if I'm going to
solder there and make as many connections as possible without messing with
the original coated soldered connections.  I'm open to other methods if
there is some experience that would simplify this task,  thanks,  Dan.

Dan Merz wrote:

> Hi,  sure this has been discussed before - on a 390 non-a i.f. chassis,
> there's what appears to be varnish on many of the solder joints (not
> all,  none on selectivity switch).  I am doing considerable connection
> modification to convert the filaments to the 390a  6 volt hookup.  Is
> there an easy way to clean this stuff off prior to applying the iron?  I
> have some solvents such as acetone, laquer thinner and alcohol.  This
> stuff appears to be selectively applied to various connections and not
> sprayed over the entire chassis though I can't be sure,  Dan.
>
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