This compact CD-Tuner set had a very intermitent failure. First time I returned it to the customer without being able to verify the symptom. More than one year later it comes back with same problem, according to the customer: CD skips. Again, it doesn't do this initially, but after some hours working it starts making a cyclic mute, with a period of 2 seconds. Some audio is heard for a fraction of a second, then mute, repeating this forever. No problem through headphones. Not sensitive to knocks / vibration. Same from all sources (CD, Tuner, Aux in). Looks like a S-Master amp problem instead of a CD issue.
Once opened ("design" equipment is usually not easy to disassemble/reassemble, and this one is a good example) I detect a dry leakage around C501, a slow discharge double layer capacitor (ELNA 0.22F/5.5V) used to backup memory (settings? radio presets?). This leakage has affected a few SMD around it and, more importantly, a lot of pins of IC500 (main controller) at side of pins 1-30. Solder looks dark and dirty. About 10 of these pins go directly to the S-Master controller IC301.
I've cleaned the board thoroughly with IPA, toothbrush and cloth (the other side too!). Slightly brushed pins of IC500 with fiberglass brush, apply flux and ressolder all pins 1-30. Same with affected SMD resistors and caps. Replaced C501 with a new one.
I'll wait for a few days of testing before celebrating it, but looks very promising. It's not the first time that I repair a failure caused by a leakage of this kind of special caps.
Once opened ("design" equipment is usually not easy to disassemble/reassemble, and this one is a good example) I detect a dry leakage around C501, a slow discharge double layer capacitor (ELNA 0.22F/5.5V) used to backup memory (settings? radio presets?). This leakage has affected a few SMD around it and, more importantly, a lot of pins of IC500 (main controller) at side of pins 1-30. Solder looks dark and dirty. About 10 of these pins go directly to the S-Master controller IC301.
I've cleaned the board thoroughly with IPA, toothbrush and cloth (the other side too!). Slightly brushed pins of IC500 with fiberglass brush, apply flux and ressolder all pins 1-30. Same with affected SMD resistors and caps. Replaced C501 with a new one.
I'll wait for a few days of testing before celebrating it, but looks very promising. It's not the first time that I repair a failure caused by a leakage of this kind of special caps.
