These are my rough notes on the Soyuz clock. Don't expect them to make a lot of sense, but I'm providing them in case they are interesting.

Board 1: This is a schematic of the switching power supply board.
Inductor E (upper left) is the output stage of an inverter powered by the 28V supply. It generates +/- 15 volts (probably) for the
op amps and a second supply for other control circuitry.
Op amp K takes the pulses from the inverter and clips them based on the feedback signal, generating the PWM signal for the switching power supply. This signal is connected to transistor G (middle of page) and drives isolation transformer B.
The output of transformer B, just to the right, powers the "driver" transformer which is the main switching transistor.
This sends pulses to transformer C (lower right), which generates two 5 volt outputs using a forward converter topology.
That is, diodes M and N rectify the first output, and inductor A and capacitor C1 filter it. This output powers the TTL logic.
The parallel output with T, L, D, and C2
powers the LEDs and relay.

Power board 2 receives the external power inputs. It has filter capacitors. It also has a linear regulator IC (pins 1-16) to generate
(probably) 15 volts for use by board 1. It also has the relay (upper left) to signal the clock's alarm time.

Board 3: This physically represents the wiring of board 3. Tracing wiring is very tedious because of the conformal coating, so I
stopped tracing it once I had some idea of the board's function. This board implements the counters for either the current time or the
alarm time, I'm not sure which. There is a lot of logic to handle setting of the clock.

Board 4: This board selects if the current time or the alarm time is to be displayed. It also checks if the alarm time has been reached.

Board 5: This board is similar to board 3, but I traced out more detail. The symbols at the top left indicate the different digits of the
time, with low digit of seconds at the top (circle), and top digit of hours at the bottom (stored in a flip flop, not a counter).

Board 5 schematic: I traced out the rough outline of how the various counters are controlled, and carries propagate from one digit to the next.

Board 6: This board receives external timing signals. It also generates digit blanking signals, which I don't understand.

Board 6 schematic: This is the circuitry that receives the external timing signals and uses either them or the internal timing signals. This circuit has been modified on the PCB and doesn't make sense. For instance, the logic gate in the lower right has its output disconnected. Either they did something very strange to the circuit, or I'm missing something.

Board 7: This generates the 1 megahertz clock and divides it down to 1 hertz. It also implements the stopwatch and handles the stopwatch start, stop, and reset signals. 

Board 7 schematic: This is my attempt to figure out the isolation circuit that receives the external start, stop, and reset signals.
There's some weird amplification or pulse shaping going on. The quartz crystal oscillator circuit is in the middle right and lower right.

Board 7 schematic: This is the state machine for the stopwatch. It is strange because the states for the stopwatch button are handled by a counter chip that is incremented when the button is pressed, moving between start, stop, and reset states. But the external stop, start, and reset signals are implemented through three latches and some control circuitry. The three states are represented by one of the latches being low. The purpose of this complexity is so the button on the clock can't override the external controls.

Board 8: This board has the 7-segment driver chips for most of the digits. The upper part shows the mapping between the driver IC pins (e.g. IC3p4), the digit bit (e.g. D1), and the other end of the wire (e.g. 4-25, pin 25 on board 4). The lower parts is some rough notes on board 9, the remaining two driver chips.

The next page is a partial mapping of the wires between each board, from board 1 to board 7. Something like 5 -> 4-1 means that pin 5 on the board is wired to pin 1 on board 4.

Display: This page attempts to figure out how the 7-segment displays are wired up. I figured out which digit was which and then stopped.

The next page shows the wiring of the panel switches in the lower left. The lower right shows the pinout of the external connector. The upper part is some rough notes on which boards the LED digits are wired to.