This thread makes a comment about the triac in the RS-1
https://ogrforum.ogaugerr.com/t...nc----not-for-resale
I have no knowledge about the RS-1 but the triac used in the MTH Z-controllers which have similar power ratings are about $1-2. If no one else comes forth with specific info, open it up and post a photo of the board. We can at least tell you which part is the triac and you should be able to read the markings on the component to find a replacement.