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Technics SA-300 with a constant sound on left channel

I was just listening music through my record player and all of the sudden my left speaker start to make a constant sound, like a "bmmmmmm", I replaced both fuses and still getting that noise, on both remote and main left channel. What should I do? What should I replace? Thanks!



Re: Technics SA-300 with a constant sound on left channel

A constant humming is not a good sign. Could be a problem with the power supply or a bad component in the amplifier. If the problem is only with the turntable, then it may be a bad ground connection in a cable or at the headshell.

Re: Technics SA-300 with a constant sound on left channel

Unfortunately, the humming is constant with all the inputs, radio, aux, or phono...

Re: Technics SA-300 with a constant sound on left channel

Constant Hum on a channel, with all inputs points to a problem with the outputs or driver stage.

Re: Technics SA-300 with a constant sound on left channel

Actually looking at the service manual. This unit uses a hybrid output IC not discreet output transistors and drivers. It's not uncommon for these IC's to fail, and either cause a hum, or blow fuses.
The chip is a "STK0039"

Re: Technics SA-300 with a constant sound on left channel

I checked my inventory ( I have a lot of original STK's) I don't have any STK0039's, but I do have a bunch of STK1045's which would work. 0039 was rated at 35W. 1045 were rated at 40W, but slightly lower DC supplies in the unit will result in probably 35W using the STK1045

Re: Technics SA-300 with a constant sound on left channel

I've been reading in other blogs and a guy said that he replaced the R625, STK0039 & Q605

Re: Technics SA-300 with a constant sound on left channel

I guess depending on how the chip fails, other parts could fail as a result. but my experience almost always was just needing to change the hybrid IC.

Re: Technics SA-300 with a constant sound on left channel

Success! One of the STK0039 was bad... flawless and crispy stereo sound coming from both Left and Right channels...

I really appreciate your help guys!