Addition to solving the problem.
After some time, after replacing the capacitors, again began to disappear MIDs and volume decrease. I, on the advice of hurghanico, checked the power supply again. And saw that the voltage at the output to 13.7 Volts!!!! Then I changed the power supply and the problem was solved. So check the power supplies first!
And before doing a check of the power supply, but not an hour after turning on, and when he lay unconnected 5-6 hours.
Now there are no complaints. Everything works fine!