Recently, I came across an electronic meter with issues (common in old meters) — the scales were not lighting up!

Patiently!
Carefully disassemble until you reach this state.

Next, I replaced all capacitors on the board because they often dry out and lose capacitance due to age, which can cause the scales to malfunction.
Replacing the capacitors didn't help, so I continued investigating the issue.
Very carefully examine both boards for cold solder joints, burnt components, and corrosion (especially under the displays).
As a result of the inspection, I noticed one suspicious spot right under the fuel display.

Visible is a suspicious residue on the track. To access it, you need to unsolder one side of the display.
It turned out that the capacitor had leaked, electrolyte got onto the track and damaged it. Cleaned up, soldered, replaced the capacitor, re-soldered the display in place
Test... The scales lit up. But not all. The daily mileage does not light up. Keep digging.
Again, carefully search for faults on the board and find them under the daily display.
Unsolder the display again, clean it, solder it back. Reassemble the display and check it.
Check... And there it is! Hurrah! Everything shines like a Christmas tree. You can start reassembling the meter.
Such a little garland!

All the best to everyone! If anyone needs help fixing their meter, I'm here. Write to me.
P.S. To power the meter, just connect one positive to the first contact in the plug and ground it to the aluminum radiator. The third photo shows this.