[Heathkit] sb200 R15 question

[labernathy]

I'm working on an old SB200. In the process of changing out the bias
cap (C3) and C19, I found that r15 (1.5 ohm 1/2 watt) was in two pieces.

I have some questions:
1. Any ideas as to what would cause this resistor to overheat and break?

2. How critical is the resistance, will 2 ohms work just as well?

3. Is this resistor expected to open as a "safety device"? I know
that in some Kenwood xcvrs, a resistor doubles as a fuse and changing
to a higher wattage unit can shift the failure to an expensive part.