Gang, I'm the original owner of a CR-620. Never over-worked, and always treated well. The only maintenance performed on it during its life was to clean the pots with Deoxit in attempt to fix "scratchiness", which worked perfectly.
Turned it on in August 2018 and, low and behold, the output relay never kicked in. Checked a lot of obvious stuff -- fuses, disconnected speakers, etc., with everything checking out. Still no relay response, so I think it's stuck in protection mode. The dial lamps and LEDs all light up. With the exceptions noted below, the entire board looks decent. Very clean, no burn spots, no bulging caps, etc. Solder junctions for the relay all look good.
I combed the threads on AK and began to suspect TR802, which is a 2SD234 attached to a u-shaped heat sink. Upon inspection of the back of the board, I noticed that the 3 solder junctions for TR802 showed evidence of excessive heat -- degradation of the solder and some rosin surrounding the junctions. Noticed the same for C802, 1000uF 50V. So, based solely on physical evidence, I replaced TR802 with a TIP31A from Mouser, and I replaced C802 with a Nichicon PW Series, exact same values, and also from Mouser. Still no go. Relay will not kick in. I never tested the old 2SD234, but I did test C802 after it was removed, and it was definitely bad. I know, I know. Stupid to run around replacing components before they test bad. I guess I got lucky on C802.
I absolutely adore this old CR-620, my first hi-fi component, and would love to save it. Any advice you guys could provide would be greatly appreciated. I have the full schematic (can share if need be). I'm a newbie at electronics. I have a decent multimeter and know how to use it, but I have no skill with testing components in place. I might be able to do some testing with guidance. I basically don't know where to go from here, and I don't have a trusted shop I can ask for help or repair. Again, any advice you could provide would be greatly appreciated.
Turned it on in August 2018 and, low and behold, the output relay never kicked in. Checked a lot of obvious stuff -- fuses, disconnected speakers, etc., with everything checking out. Still no relay response, so I think it's stuck in protection mode. The dial lamps and LEDs all light up. With the exceptions noted below, the entire board looks decent. Very clean, no burn spots, no bulging caps, etc. Solder junctions for the relay all look good.
I combed the threads on AK and began to suspect TR802, which is a 2SD234 attached to a u-shaped heat sink. Upon inspection of the back of the board, I noticed that the 3 solder junctions for TR802 showed evidence of excessive heat -- degradation of the solder and some rosin surrounding the junctions. Noticed the same for C802, 1000uF 50V. So, based solely on physical evidence, I replaced TR802 with a TIP31A from Mouser, and I replaced C802 with a Nichicon PW Series, exact same values, and also from Mouser. Still no go. Relay will not kick in. I never tested the old 2SD234, but I did test C802 after it was removed, and it was definitely bad. I know, I know. Stupid to run around replacing components before they test bad. I guess I got lucky on C802.
I absolutely adore this old CR-620, my first hi-fi component, and would love to save it. Any advice you guys could provide would be greatly appreciated. I have the full schematic (can share if need be). I'm a newbie at electronics. I have a decent multimeter and know how to use it, but I have no skill with testing components in place. I might be able to do some testing with guidance. I basically don't know where to go from here, and I don't have a trusted shop I can ask for help or repair. Again, any advice you could provide would be greatly appreciated.