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

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.)

"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.

"Mark D. Zacharias" wrote in message
et...

"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.

Last time I had a problem very similar to this, although not on a Yammy
specifically, it was the 10.7 MHz filter that was internally intermittent.
When it was wrong, you could get it back by sharply rapping the filter case
with a screwdriver tip. Just as you say, it would go ok for hours, and come
and go on its own.

Arfa

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.

In article .com,
"rv31rv" wrote:

So radio shack sell liquid flux? After removing & replacing the ribbon
cables, it has worked for 7 hours straight.

That's great! I don't think radio shack sells anything but consumer crap
made in China anymore. They stopped catering to hobbyists 25 years ago,
or more.

Flux is a tool. You can beat a hole in something with a hammer and a
screwdriver, but once you've tried a drill, you'll *probably* stick to
that method.

If you're going to solder, a good quality soldering iron outfitted with
a *shiny* new tip, and a little squeeze bottle of liquid flux will make
you feel like you've discovered jesus if you've been fumbling along
without those things.

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.

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

So radio shack sell liquid flux? After removing & replacing the ribbon
cables, it has worked for 7 hours straight.

That's great! I don't think radio shack sells anything but consumer crap
made in China anymore. They stopped catering to hobbyists 25 years ago,
or more.

Flux is a tool. You can beat a hole in something with a hammer and a
screwdriver, but once you've tried a drill, you'll *probably* stick to
that method.

If you're going to solder, a good quality soldering iron outfitted with
a *shiny* new tip, and a little squeeze bottle of liquid flux will make
you feel like you've discovered jesus if you've been fumbling along
without those things.

I'd guess I have a quarter million or so solder joints under my belt and I
would say that most of the time the flux in the core of good quality solder
is more than adequate. The extra bit of solder is also useful where too
little was deposited in production, as is often the case. Liquid flux is
useful, but the extra residue makes it harder to be sure that you have a
good result. I always keep it handy, but rarely need it. Correct
temperature, a clean tip that is as large as the work will allow, and decent
solder work just fine most of the time.

Leonard

In article ,
Smitty Two wrote:
If you're going to solder, a good quality soldering iron outfitted with
a *shiny* new tip, and a little squeeze bottle of liquid flux will make
you feel like you've discovered jesus if you've been fumbling along
without those things.

I've not heard of liquid flux - apart from the stuff used for engineering
soldering which is rather corrosive for electronic work. What is it?

--
*Funny, I don't remember being absent minded.

Dave Plowman London SW
To e-mail, change noise into sound.

"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.

"Mark D. Zacharias" wrote in message
et...

"Smitty Two" wrote in message
news
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.

I've used liquid flux, and it makes one's job easier, especially when
soldering a postage stamp IC. Not required for standard resoldering jobs,
though.

Just requires more cleanup afterwards.

Mark Z.

Agreed. I too have 35 years' worth of professionally soldered joints under
my belt, and have never found that I need anything other than good quality
flux cored solder to make perfect joints - that is to date, and with one
important exception. If you replace large LSIs, as one of the other posters
said, liquid rework flux is essential. If you've never used it for this, you
wouldn't believe how much easier it makes the job. It makes the solder flow
to the pins and pads so well, that it's virtually impossible to finish up
with shorted pin clusters, unless you apply ridiculously large amounts of
solder, or use an inappropriate gauge.

The situation is changing however. The new lead-free solder that's now being
used has hugely inferior wetting characteristics, and the fact that it has
to be got almost 50 deg C hotter before it melts, means that the flux in the
cores is slower to activate. I would suggest therefore, that the use of
additional liquid flux with this new material, may well become the norm.
Liquid flux can actually be quite expensive, but some time ago, I found an
Electrolube product called SMFL200D, which is a 200ml aerosol, and very
reasonably priced. You use such a small amount of it, that I am still on the
first tin. Highly recommended, if it's available in your part of the world.

Arfa

In article ,
"Dave Plowman (News)" wrote:

In article ,
Smitty Two wrote:
If you're going to solder, a good quality soldering iron outfitted with
a *shiny* new tip, and a little squeeze bottle of liquid flux will make
you feel like you've discovered jesus if you've been fumbling along
without those things.

I've not heard of liquid flux - apart from the stuff used for engineering
soldering which is rather corrosive for electronic work. What is it?

I think it's a mixture of tree sap and alcohol. Google Kester 1544.