After installation of the battery pack and tweaking the VCO potentiometer, I thought I was done with the inside of my newly acquired Yamaha tuner. Turns out I was a bit premature in that assessment.
When I was in there last time, I took the opportunity to clean off the corrosion from the leaking battery that had migrated onto the back of the main circuit board and had dribbled down its length. (It must’ve been sitting on it’s side for years in storage.) I buttoned everything back up after the cleaning and didn’t think anything more of it.
Well, the next day when I powered it up, all the lights came on, but there was no sound coming out. Signal strength was good. Tuning was locked in, but there was no stereo light. Perplexed, I turned the power off and turned it back on. It started working normally.
I figured it was some temporary glitch and went on about my day. The next morning, I had the same problem. The same thing (off/on) fixed it again. Okay, this wasn’t just a one-time glitch.
Two days ago the single off/on trick stopped working. It took several tries to get it working properly.
Yesterday, nothing got it up and running normally other than to turn it on and just let it sit for about five minutes. It then spontaneously started working on its own.
This morning, faced with the same situation, I decided to go online and see if I could find any clues to why this was happening. It turns out the main power supply area of the circuit board was one of those areas affected by the battery corrosion (apparently this is a pretty common issue that can affect any number of functions in the tuner). So I disconnected everything and popped the cover and took a good look at all the traces and solder joints in that area (including where the corrosion had dribbled down the length of the board). The traces all looked okay, but some of the solder joints looked suspect. So I reflowed the ones that looked dodgy. I powered it up and as always, I breathed a sigh of relief when I didn’t see smoke rising. And everything worked.
At this point I think—er rather, I’m hoping—that it was simply one (or more) cracked/corroded solder joints that needed to heat up and expand ever so slightly to make proper contact. (Being the power supply area, it does generate a bit of heat.) Everything is all warmed up now so I guess the test will be tomorrow morning when it’s powered up cold.
UPDATE: 11/21: It worked!
UPDATE: 11/23: Nope. It was turned off for more than 24 hours and when I turned it on this morning it was back to its old behavior. That means there’s a bad capacitor somewhere in the circuit path, but considering there are 271 capacitors on that board tracking it down without any electronics knowledge is an impossible task—or at least one best left to an expert (which I am most certainly not.) Now all I have to do is find a local expert…