THE INFAMOUS SONY INTERMITTANT TUNER

     When the solder connections break loose inside the tuner, symptoms
range from dead channels (just a few or a whole band, etc.) snow on all
channels, oscillation, screech in sound, blank screen, etc. Any or all of
these symptoms can be intermittant with time or temperature. The repair
involves removing the tuner and the little metal box sitting next to it
and resoldering the grounds and feed-thru connections. Unsolder the tuner
and IF pack from the main board and pull the covers. Resolder inside the
tuner around the perimeter with a large tip iron (I use a Weller WTCP
with a PTE-8 800 degree screwdriver tip). I find it easiest to heat the
case from the outside and apply solder to the inside when doing the
grounds. Always apply new solder... don't just reflow the old. Check and
resolder any other connections in there that look flaky. BE CAREFUL
around surface mount components and don't move any coils when you work...
it will detune them. You might want to use a smaller iron for rework
inside the tuner. Resolder the feed-thru connectors. The trouble spots in
the IF pack are the little coils... they need to be resoldered. Solder
also the feed-thru connections. Put the covers back on and reinstall the
tuner and IF pack.
     As preventive maintenance, examine the main PC board. Look for bad
solder on heat producing components like power transistors, power
resistors (1 watt or more) and large inductors like the flyback, H driver
transformer, etc. I just resolder all of that stuff anyway, no matter
what it looks like. With power resistors, you will find they don't want
to solder because they normally run hot and that heat oxidizes the leads.
You can either pull the part and scrape the leads, or (as I do) apply
more solder and use a hotter than normal iron. You don't want to overheat
the PC board or the pads will start to lift off. A larger iron doesn't
need as much time on the connections as a lower wattage unit. After you
have taken care of that stuff, the set should be very reliable from then
on. Kind of a grunt, but worth it. Avoid inhaling the fumes.. use a small
fan to blow them away.

Ray Carlsen
CARLSEN ELECTRONICS... a leader in trailing-edge technology.