I think those 2sa912s run hot. Mine desoldered themselves from the board. You can pop the cover off and reach them without removing the faceplate and board. Wiggle them and look to see if they are soldered well, or try reflowing them. You can replace them with KSA1220AYS. You will need to drill out the holes and then pad are small. Mine were gone so I had to scrape some green off and solder to the trace.
You sir are a true Gentleman and a Scholar. I tried re-flowing the transistor contacts and it was a no-go. By sheer blind luck I had mis-ordered the transistors on this refurb effort as per the recommended list on this thread (Post #14):
http://www.audiokarma.org/forums/index.php?threads/sa-7800-with-burnt-out-resistors.487176/
It recommended the following transistors and substitutes:
Transistors,,,,,
"1,2",2SA1114,KSA992,,,
"3,4",2SC1117A,KSC1845PBU,,,
"5,6",2SA912,KSA1142 + heatsinks,,,
This is actually my first re-cap and repair effort on my own (previously I had installed a number of old Quad kits like the 34, 44, 306 and FM4 which came with everything and instructions - kinda like recap by numbers). The repair part was the u/s left channel of the Phono which I didn't think I would be able to do so was going to take it in to a tech if I couldn't sort it out myself.This was really my first ever attempt at finding a suitable order list and then ordering from an online parts seller (Digi-key and now I am looking at Mouser Canada). I had not messed with transistors before this and only ordered two of the above not realizing it called for 6 Transistors. One of the two that I received was the KSA1142 which also appears to be a replacement for the 2SA912 you mentioned as per the order list. I thought they were one in the same and didn't realize the 5,6 referred to Q5 and Q6 and i should have ordered two. It was Q5 that was duff. I had bought some thumb drills on a recommendation from the local electronics store and sure enough I used one to bore out the holes as you mentioned. It was a good buy! I plugged the amp back in and hooked up the Turntable and "POW", it frikkin' worked on both channels with the phono!
This was the final thing to compete the refurb/repair and I am absolutely tickled pink. I will of course order the balance of the transistors and install them when they arrive to finish it up. It sounds real real good now....
Next I will be doing my matching TX-7800 and then a SA-8500II so thank you very much for getting me past this final hurdle.