There should still be parts available for your SMR-2A3. If possible, you might just want to order a new C4S board with associated parts, as removing components can be tough.
If I had to fix the board, I would replace the 2N2907, MJE5731A, and blown resistor, then call it good. The LED's should be fine if they don't look obviously blown, and the 300K resistor is pretty impervious in this application.
-PB
« Last Edit: February 14, 2017, 08:19:48 AM by Caucasian Blackplate »
Paul "PB" Birkeland
Bottlehead Grunt & The Repro Man