Hello guys, I am out of ideas and I need some help.
So my recently bought Technics SU-8080 is working fine except for the fact that it picks up radio stations ( quite audible ) instead of being dead silent at 0% volume and also has a constant hum. The hum and radio volume is louder when I change position, any touch anywhere on the chassis will create extra hum. The chassis connection to the RCA sleeve is solid, so is the chassis connection to the power supply caps. The unit has been recapped EXCEPT for the power supply caps, the symptom stays exactly the same. It uses opamps in the tone section. One more thing to mention, when I take the RCA jacks off, the sound completely goes away. If I plug in any RCA cable, it will hum and catch radio, even if it's not that specific input selected from the input selector. Also, the volume control does not affect this sound. Even with the RCA cables disconnected, when touching the jumper on the back from pre-amp to main amp it will pop on my touches.
The sound is the same on both channels, and it doesn't even matter which channel I connect to the RCA, connecting just 1 RCA will bring the noise on both. The same cable produces no noise on my other receivers. This is not a source issue or cable issue, this is something entirely related to the unit itself. I can clearly see that this is a ground issue, however the ground connections are solid at almost 0 ohm.
All pots and switches have been cleaned and using them does not change the sound. The only thing that does is the Muting button which makes the sound much dimmer but also the input signal so..
What is going on , I am out of ideas ?
So my recently bought Technics SU-8080 is working fine except for the fact that it picks up radio stations ( quite audible ) instead of being dead silent at 0% volume and also has a constant hum. The hum and radio volume is louder when I change position, any touch anywhere on the chassis will create extra hum. The chassis connection to the RCA sleeve is solid, so is the chassis connection to the power supply caps. The unit has been recapped EXCEPT for the power supply caps, the symptom stays exactly the same. It uses opamps in the tone section. One more thing to mention, when I take the RCA jacks off, the sound completely goes away. If I plug in any RCA cable, it will hum and catch radio, even if it's not that specific input selected from the input selector. Also, the volume control does not affect this sound. Even with the RCA cables disconnected, when touching the jumper on the back from pre-amp to main amp it will pop on my touches.
The sound is the same on both channels, and it doesn't even matter which channel I connect to the RCA, connecting just 1 RCA will bring the noise on both. The same cable produces no noise on my other receivers. This is not a source issue or cable issue, this is something entirely related to the unit itself. I can clearly see that this is a ground issue, however the ground connections are solid at almost 0 ohm.
All pots and switches have been cleaned and using them does not change the sound. The only thing that does is the Muting button which makes the sound much dimmer but also the input signal so..
What is going on , I am out of ideas ?
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Hello,
I don't have this particular model, but a later SU-V8 which presented same symptoms.
There are a few screws which connect ground traces from some boards to the chassis, check their contacts. Also, check Phono GND screw - this one was my problem. And gnd sleeve of signal wires to be soldered exactly where they're supposed to be.
Regards.
I don't have this particular model, but a later SU-V8 which presented same symptoms.
There are a few screws which connect ground traces from some boards to the chassis, check their contacts. Also, check Phono GND screw - this one was my problem. And gnd sleeve of signal wires to be soldered exactly where they're supposed to be.
Regards.
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The RCA shield acts as an antenna because the low impedance RCA shield-to-chassis path is broken. You need to find out exactly where. Usually, it's the oxidation to blame. Post well-lit, in-focus photos of the inards, and we will help further...