F4 dc offset problem

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Hello everybody , i have a problem with my f4 amplifier.My right chanel the dc offset when i turn on i have -70mv and after 3 hours is near 0mv , but with my left chanel i have some problems when i turn on everytime i have different value and and goes up and down very fast and the las value was from 86mv to 120mv in 10 minutes.

Thx for help, greetings from Romania.
 
as I said in PM - post pictures

double check mounting of outputs on heatsink - are they tightly & evenly screwed on heatsink , check all solder joints (including all resistors in biasing network)

replace TL431 - it's cheap anyway

luckily - your problem isn't connected to input Jfets in any way 😉
 
I had similar problem caused by P2 trimpot (500 ohm). Change it then. Besides I noticed that it's very easy to set DC offset very close to zero within range of -3 to +3mV or smaller. If problem still exist replace TL431 as Zen Mod said.
 
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