SX 1050 - another dodgy channel problem!

[ex brickie]

I bought one of these a few months back - lovely cosmetic condition, all original boxes, and sounded great (I had some radio reception issues but largely resolved those).

Recently, one (left) channel started going quiet and distorted. But with no consistency. Sometimes worked, sometimes cut out, sometimes ‘half’ the volume of the other channel.

Now the right is playing up. If I switch on sometimes both channels are fine for 1 minute, then they are both fade to very low output (almost nil). I tried connecting something to Aux. Same problem.

Is this likely to be the same issue as the thread about the dead channel on this receiver? I don’t have any real electronics knowledge (apart from knowing the difference between a capacitor and a resistor!) so it will need to go to someone who fixes vintage stuff. I’m in the UK. I would like to get an idea of where to start looking - I’m comfortable taking the hood off (unplugged of course!) and having a nose around. I also have a multi meter if someone gives me a step by step guide what to try out

To be honest I don’t mind spending a bit of money on it and get a number of parts replaced at once. Would be good to know where to start looking and fixing

I have a detailed manual with circuit layouts but may need a parts guide at some point

Thanks folks!

 

[Watthour]

That's all good information. The fact that the channels drop out, distort, and sometimes return to normal operation might indicate that there are no real issues with semiconductors. If an output transistor were to fail, it would be unlikely that operation would return to normal sometime after that. Some of the upstream small signal transistors could potentially have thermal problems, and that might produce the symptoms you describe, so it cannot be ruled out completely, but it is very important to perform some basic service to assure that the functions of switches and potentiometers are reliable so that we don't end up chasing our tails. Once the controls are cleaned, exercised, flushed, and lubricated the focus can move to other components, if necessary.

One advantage of the SX-1050 is that the output power amplifier section can be de-coupled from the input and pre-amplifier sections. If there is another source available, that can be connected to the power amp section to help determine whether the main problem is within the power amp, or the pre-amp sections.

 

[ex brickie]

@Watthour are there any 1050 parts that are impossible to get? I realise your response will be from a USA perspective (I’m in the UK) but good to know whether there is anything unobtanium

cheers

 

[Watthour]

"Impossible" is something that the AK community doesn't understand. "Difficult" is only a matter of degree.

My guess is that anything you may find causing the problems you describe would be easily replaced by modern components which are readily available. Going out on a limb, and without any real feedback from analysis, I'm guessing you will find some failed or marginal capacitors, some thermally failing transistors, and possible fading resistors. Replacement components can be selected to potentially make it even better than it was when new.