Technics SA-401 stereo balance issue - Page 1
Forum section: electronics / repair

author: zierro
author_rank: Newbie
timestamp: November 30, 2018, 10:05:25 pm
content: 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.htmlAny help would be appreciated, thank you.

author: Specmaster
author_rank: Super Contributor
timestamp: November 30, 2018, 10:57:06 pm
content: Quote from: zierro on November 30, 2018, 10:05:25 pmI 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.

author: fixy88
author_rank: Contributor
timestamp: December 01, 2018, 04:38:17 am
content: When you connect the left speaker and turn it all the way up, does it sound normal, or distorted?

author: shakalnokturn
author_rank: Super Contributor
timestamp: December 01, 2018, 09:31:33 am
content: 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?

author: Simon Spiers
author_rank: Regular Contributor
timestamp: December 01, 2018, 12:27:18 pm
content: 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.

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 03, 2018, 01:55:57 am
content: 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=schematicsFeed 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.