Studer 169 help psu

Hello everyone. I'm restoring a Studer 169.
This model has the external power supply and an internal DC / DC converter.
A problem appears over time, the tension is coming down.
I do not know what produces it.
An exessive consumption in some module? Although I have removed one by one ...
DC / DC plate? Neither seems to be, I have connected another 12V PSU and works well.
A problem in the external PSU?
A detail, see the photos.
The two coils of the secondary, should not go in parallel? Same colors?

Welcome.

> the tension is coming down.

From 14.3V to 1V? Or from 14.3V to 14.1V?

Basic debugging. What is the voltage across C1 C2? Has to be "more than 15V", probably over 20V, but not like 35V. If C1 C2 have dried-up it will be low and VERY unsteady (100Hz ripple).

We could go on and check the uA723 for 7.15V, and R14 making about 0.2V into pin 10..... but these days _I_ would grab the big axe, clear the old wood, and drop in a 7815. It gives the right voltage (I'm sure "14.3V" was convenient not essential), is self-protecting against over-current and for over-heat. It will fit where the MJ2955 is (just use one screw).

Technical note: taking pictures of computer monitors is not as good as using a "screen grab" tool. Screen-grab gets the full range white to black without the 'moire' pattern. Some screen-grab tools also let you re-size down from enormous 4000-pixel images.

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Hi. Thanks for the reply.
Sorry, I did not describe the whole situation.
The voltage drops to approximately 5 volts.
All the condesadores are new, including c1 and c2, there are 24 volts. But transistor Q1 does not pass the correct voltage over time.