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
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.
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. :)
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.
"Mark D. Zacharias" bravely wrote to "All" (12 Feb 06 13:54:08) --- on the heady topic of "Re: Yamaha R8 Receiver Tuner Problem"
MDZ> From: "Mark D. Zacharias" MDZ> Xref: core-easynews sci.electronics.repair:358141
MDZ> I've used liquid flux, and it makes one's job easier, especially when MDZ> soldering a postage stamp IC. Not required for standard resoldering MDZ> jobs, though.
MDZ> Just requires more cleanup afterwards.
Roll your own liquid flux. Paste flux dissolves in alcohol. Add flux to the alcohol until as thick as desired. Pour into a small syringe and squirt it onto the solder work as needed. Easy as 3.141592654...
... That was a fascinating period of time for electronics