yk_heli
New Member
Hello all! I'm a new member but have been reading this site for the last two years since I first got exposed to vintage audio systems. I am a happy owner of both a Yamaha CA 610ii and a CR 620 and right away fell in love with the natural sound and the aesthetics of the yammies.
A few weeks ago my girlfriend was listening to the radio on the CR 620 while I was at work, and she heard a fairly loud pop before the system went dead silent. Later that evening I tried to turn on the system but the protective relay would not click. (she was not sure whether the pop came out of the receiver or out of the speakers)
I decided to open it up yesterday and check out what would be wrong, along with browsing AK and checking out the service manual schematics. The unit is very clean and I did not spot any blown fuses, leaky/bulged capacitors, broken solder joints, or improper grounding . I tried to turn it back on and the relay clicked miraculously. I checked both idling currents after a 10 min warm-up on AUX and a low volume and set VR701 and VR702 to 8mV as specified in the manual as they were off (11-12 mV).
I remembered that the unit would always run exceptionally hot after a while and I was not comfortable with this "easy" fix for future listening sake; there had to be something else wrong. Therefore I let it cool off over night and went to check the idling current again today, measured in 5 min intervals. Strangely, the idling current between T3-T4 (for VR702) remains steady at 9mV whereas between T1-T2 (VR701) the current drifts to over 160 mV!! (attached graph).
I couldn't find anything on AK about drifting idling currents in Yammies way over the rated values; therefore this post. What is going on and what to do? I am somewhat tech-savvy but unfortunately cannot bring it to a professional (I live in subarctic Canada).
A few weeks ago my girlfriend was listening to the radio on the CR 620 while I was at work, and she heard a fairly loud pop before the system went dead silent. Later that evening I tried to turn on the system but the protective relay would not click. (she was not sure whether the pop came out of the receiver or out of the speakers)
I decided to open it up yesterday and check out what would be wrong, along with browsing AK and checking out the service manual schematics. The unit is very clean and I did not spot any blown fuses, leaky/bulged capacitors, broken solder joints, or improper grounding . I tried to turn it back on and the relay clicked miraculously. I checked both idling currents after a 10 min warm-up on AUX and a low volume and set VR701 and VR702 to 8mV as specified in the manual as they were off (11-12 mV).
I remembered that the unit would always run exceptionally hot after a while and I was not comfortable with this "easy" fix for future listening sake; there had to be something else wrong. Therefore I let it cool off over night and went to check the idling current again today, measured in 5 min intervals. Strangely, the idling current between T3-T4 (for VR702) remains steady at 9mV whereas between T1-T2 (VR701) the current drifts to over 160 mV!! (attached graph).
I couldn't find anything on AK about drifting idling currents in Yammies way over the rated values; therefore this post. What is going on and what to do? I am somewhat tech-savvy but unfortunately cannot bring it to a professional (I live in subarctic Canada).
