Hello,
The story is the following: back two years ago, my restored HF-81 developed a static noise in the left channel. Usually, wiggling the left 12AU7 cured the problem. Forward now to 2017: it was now like a thunder noise and by pushing slightly on the chassis, I was able to cure it for a day or two.
Tired of this, I opened the beast and finally discovered that a ground solder joint (made by me) was flaky. One wire going from the selector switch to this ground lug (a lot of stuff on this one BTW) was losing contact sometimes, thus the scratching noise. Reflowed correctly and now, all is ok.
The story is the following: back two years ago, my restored HF-81 developed a static noise in the left channel. Usually, wiggling the left 12AU7 cured the problem. Forward now to 2017: it was now like a thunder noise and by pushing slightly on the chassis, I was able to cure it for a day or two.
Tired of this, I opened the beast and finally discovered that a ground solder joint (made by me) was flaky. One wire going from the selector switch to this ground lug (a lot of stuff on this one BTW) was losing contact sometimes, thus the scratching noise. Reflowed correctly and now, all is ok.
