Sony TA-1010 noisy phono circuit
 

Hello All,

I've started to have a look at my Sony TA-1010 amplifier, to see if I can sort out the noisy phono circuit.

Playing through all of the other inputs, it is absolutely fine. But when I select phono 1 or 2, the music comes out crackly / distorted.

I've done a quick visual check of the capacitors on the pre-amp and power amp board. None are throwing up any issues that I can tell.

Also I have tried to find information around various sites and some point toward faulty transistors. Apparently the type of transistor on the pre-amp are prone to failure. I happened to have some new equivalent spares lying around, so fitted those 4. However, it didnt make any difference.

So instead of chucking more parts at it, i wondered if anyone would have any ideas of where to go next?

manual is linked at https://audio-circuit.dk/downloads/s...010-int-sm.pdf

Re: Sony TA-1010 noisy phono circuit
 

What turntable/record deck cartridge are you using for the phono inputs ?

This amplifier is intended to be used with Moving Magnet (MM) cartridges.

If you are using an old fashioned Ceramic or Crystal cartridge, then it almost certainly would overload the phono inputs and cause distorted signal.

If you are using a modern Moving Coil (MC) cartridge, then it would not give good results into a MM phono input.

David

Re: Sony TA-1010 noisy phono circuit
 

C101 and C106 in the phono equalizer stage are 1uF electrolytic capacitors.

Small electrolytic capacitors have a tendency to dry out.
They are not the easiest components to verify as working OK.

If there was room on the circuit board I would try to replace them with film type capacitors.

The signal from a moving magnet cartridge might be in the region of 5mV.

Re: Sony TA-1010 noisy phono circuit
 

Ah, ok. Maybe that explains it then.
I initially plugged in a random 90's sony turntable, Which ive now sold.
I then plugged in an RCA to 3.5mm jack into a digital walkman :-[. Just as a test.

I never realised this would do this and it was only compatible with a certain input type.

Glad I put the message on here now and did think it was weird the other inputs are perfect.

Re: Sony TA-1010 noisy phono circuit
 

Thanks for the quick replies, its appreciated.

Re: Sony TA-1010 noisy phono circuit
 

The input sensitivity of these Phono inputs is 1.2mV at 47kOhms so a very sensitive input, the TA-1010 specification states that 30mV is the maximum input capability.

If the Walkman signal was anywhere near line level, then it would easily overload a phono input.

David

Re: Sony TA-1010 noisy phono circuit
 

Sounds like it's definitely the issue. I will try a different turntable when I have one available.

Thanks for the rapid responses, it saves a lot of time.

Thanks

Re: Sony TA-1010 noisy phono circuit
 

It's not just a case of overload distortion: you may have been lucky not to have nuked the phono amp transistors.

Re: Sony TA-1010 noisy phono circuit
 

Yeah, I've definitely learned something with these replies.
Hopefully they will be ok, as I kept the volume low (if that means anything).

Will soon find out when i get the chance to check on a suitable turntable.

Re: Sony TA-1010 noisy phono circuit
 

The bottom line is that phono inputs on an amplifier should only be used for turntable/record deck signals, in this case with a moving magnet cartridge.

Another device with low (< 30mV) signal output + matching impedance maybe could be used, but due the phono pre-amplifier applying RIAA equalisation may not sound quite right.

David

Re: Sony TA-1010 noisy phono circuit
 

Although ...
This does use use transistors KNOWN to sometimes go noisy / bad in the RIAA Eq stage. No problem if this is the case, it can be fixed for a few pennies :)

I would think the 'phones output', with the volume turned down as low as it will go (on the walkman), should not overload the input. As already mentioned, the RIAA Eq will make it sound rather unusual, like you turned the treble to maximum and the bass to minimum. Having said that, some digital amplifiers (in the walkman) don't play nice if they don't have a low enough load impedance but the better brands work just fine ...

dc

Re: Sony TA-1010 noisy phono circuit
 

Yeah, I read that these transistors have known issues. This is why i initially thought it may have been this, so changed all of them on the pre-amp. Which diagrams show are connected to phono (if im correct).

The left channel does have some random crackling at times, But the right is fine. As it happens I do have quite a few compatible transistors, from a previous repair.

Re: Sony TA-1010 noisy phono circuit
 

Surely the RIAA compensation would boost the bass and attenuate the treble ie bass to maximum and treble to minimum?

Re: Sony TA-1010 noisy phono circuit
 

Just as an aside, you can get a nice colour scan of the original Sony TA–1010 book with nice turquoise PCB track layout Diagrams in it from here, free of charge :–

https://freeservicemanuals.info/en/s...al/Sony/TA1010

Chris Williams

Re: Sony TA-1010 noisy phono circuit
 

That's the response to noise coming into the stage.

For noise created within the stage, the result isn't necessarily the same.

David

Re: Sony TA-1010 noisy phono circuit
 

Thanks very much for that.
The manual i was using, was awful. I couldn't find another, so this is perfect.

Re: Sony TA-1010 noisy phono circuit
 

I decided to replace all the transistors on the power amp board, as these are known noisy transistors.

I had a load of spares anyway, so whilst it was open i thought i might as well.

Luckily the noise on the left channel has now gone, So these must have been the culprit.