Dilshan Jayakody has written an article about Sony TC-252 reel to reel player repair:
As a first step of the restoration we remove the LA4440 module attached into that recorder and rewire the player with original wiring layouts. After rewiring we check all the transistors in that player and find-out that the couple of 2SC634 transistors are damaged in that player. Because 2SC634 is not available in the market we replace those damaged transistors with BC548 transistors.
For the front panel potentiometers we use standard 10K and 20K (log) potentiometers available in the market.
To fix motor speed problems we replace 1.5MFD + 0.5MFD multi-section can capacitor with two separate 1.5MFD and 0.5MFD (450V) AC fan capacitors.
More details at Dilshan Jayakody’s blog.