Technics SA-401 stereo balance issue

[zierro]

Hello,
I was recently given an old Technics SA-401 stereo receiver from my in laws, the only problem is that the volume balance seems to be stuck fully going to the right side. Turning the balance dial does nothing and neither does switching the speakers or input. If I only have the left speaker connected and turn the volume up all the way, sound does come out of the left speaker. Is it a problem with the balance potentiometer, or is there something else causing the problem?

Service manual: https://elektrotanya.com/technics_sa-401_sm.pdf/download.html

Any help would be appreciated, thank you.

[Specmaster]

Hello,
I was recently given an old Technics SA-401 stereo receiver from my in laws, the only problem is that the volume balance seems to be stuck fully going to the right side. Turning the balance dial does nothing and neither does switching the speakers or input. If I only have the left speaker connected and turn the volume up all the way, sound does come out of the left speaker. Is it a problem with the balance potentiometer, or is there something else causing the problem?

Service manual: https://elektrotanya.com/technics_sa-401_sm.pdf/download.html

Any help would be appreciated, thank you.

I would think that it is more likely that that you have a lost a channel of the main amplifier. You can check if the balance control is working properly by testing it with a meter set on resistance.

[fixy88]

When you connect the left speaker and turn it all the way up, does it sound normal, or distorted?

[shakalnokturn]

If you don't know the amplifier's history (was it working and suddenly stopped before being given to you?) it may not be worth the time you'll spend methodically troubleshooting.

A good starting point on HiFi of this age (who still builds HiFi today anyway?!) is to check / refresh the solders, clean contacts on all the switches and potentiometers before actually starting any real troubleshooting.
It's also a good idea to check the speaker protection relay's contact resistance.
Have you tried an external source on various inputs rather than only the tuner?

[Simon Spiers]

A number of things to try.
1 If your using an external source like a cd player ect swap the input left and right over.
2 Try another input.
3 Try headphones.
4 as said above swap speakers over.
5 it could be a dirty selector switch on the input or speakers, work them rapidly in their full extent and try again.

[mzacharias]

Troubleshooting audio is usually pretty easy. Best to use a sine wave input, 8 ohm load resistors, an oscilloscope and a (usually digital) multimeter. Service manuals would usually be available from Hi-Fi Engine or Electrotanya. For example:

https://elektrotanya.com/showresult?what=technics%20sa-401&kategoria=&kat2=schematics

Feed a signal in (1 kHz sine wave is often used) and use the scope to narrow down to a stage. The volume control is a good place to start.

From that point, often the multimeter, on a DC volts function, can give a clue as to the nature of the problem when compared to the working channel.

Asking some guys on an internet forum isn't all that likely to narrow down your problem. Troubleshooting is required.