"Bob Parker" wrote in message
...
I remember seeing intermittent FM operation in several Yamaha
receivers of that vintage. It wasn't bad soldering, but one of the
tiny trimmer caps in the FM front-end module going intermittent. I
suggest you check it out before going over all the soldering with a
magnifier.

Bob


On Sat, 11 Feb 2006 14:16:19 -0800, Smitty Two
wrote:

In article ,
"Mark D. Zacharias" wrote:

"Smitty Two" wrote in message
news In article .com,
"rv31rv" wrote:

OK, so I search for Yamaha tuner problems (intermittent FM) & find
the
threads for LC7210 problems. I replace the IC for $21.50 & same
problem! Tuner works for long periods (hours) & suddenly the signal
strength drops to "0" & white noise only, no FM stations. AM & all
else still work. I leave the unit on & it just as suddenly starts
begins working again. This is really a great receiver & want to fix
it. So: Does any one have a Schematic and any suggestions from the
experts?
Thanx - Bob

Get some very strong reading glasses *and* (NOT "or"!) a very powerful
magnifier, along with the brightest light you can find, and look for
one
tiny little cracked solder joint. It might be so tiny that you won't
be
able to see it even then, unless you wiggle the components one at a
time.

Then get some liquid flux, and reflow that joint. Don't even think
about
skipping the liquid flux. You *need* it.

(I'm not an expert, but I play one on usenet.)

More specifically, the front-end pack may need resoldering. Better if a
professional does it, but liquid flux is NOT needed. 60/40 solder
(rosin-core ONLY) contains flux already.

Mark Z.

Yep, so it does, as does 63/37, which has been the industry standard for
at least fifteen years. I stand by my assertion, though, because
reflowing the joint with liquid flux produces a solder joint that is
orders of magnitude better in every respect than just adding more
flux-cored solder. It's also a hell of a lot faster.

Those that don't believe me are welcome to try their own side-by-side
comparison. I imagine I've overseen the soldering of at least 100
million solder joints in the last 25 years, of which I personally
hand-soldered *at least* a half million, maybe five times that. Liquid
flux isn't an optional extra, it's absolutely required for good
soldering, period.

I wouldn't even know where to look for the FM section in a receiver, but
I do know something about soldering.


Ah, yes! Trimmer caps!

Had one just the other day - on a Carver receiver.

Mark Z.