Adjust SQ-507X


Be careful not to get electrocuted. Also, if you short-circuit and blow the power transistor, it will be seppuku.
 The 1971 amplifier, which is a national treasure, has not been adjusted since September 2022, and the left speaker has started making strange noises when turning it on and off.

 I was looking at old Rakuten blogs and doing image training on the subway on the way home from Sakae. Let's start after taking a bath and eating dinner. Tomorrow I have a blood test at Aichi Medical University Hospital and I'll also test the amplifier.




L side DC balance ±50mV This seems to be out of range.Remove the driver board for both LR and measure one side at a time.






The L side is -252.9mV, which is terrible.It's not good for the speakers either, so I aim for ±0mV.

 Bias has dropped from 4.0mV to 1.3mV
 It's likely to rise a bit more once it warms up, but I'll keep an eye on it for about 10 minutes before starting work.




Adjust the trimmer using a flathead screwdriver.
 The L side is finished. It's like this!




Next, measure the DC balance on the R side as well. 6.1mV is great, but the bias is low. Don't worry about raising it too much, so decide on around 3.8mV, finish, and restore.




Listen to one and do a sound check.
 Tonight is DIP THE FLAG. Listening to an indie album from 1990 with an amplifier manufactured in 1971 sounds futuristic even in 2024.

 If you ask me, we live in an era where things that are taken for granted are no longer available, so I want my life partner to have this as an heirloom and be something that remains the same.

 Me, my amp, and my work are all cool.
 This is fine.


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