This game was done in time for Halloween but with all the Joust threads at the time, I wanted to make room for other folks cool Joust restore posts. Found this amazing survivor Joust "not booting" as I was told for a good price and jumped on it.
Turned out that, as I figured/hoped...power supply issue. BR1 was melted, connections burnt up, some previous repairs as well on PS...7905 -5v reg had been replaced with NEC part(that regulated WAY differently than the original part unloaded), one LM723 IC regulator chip not original, R10 was removed probably to boost voltage on those oxidized/burnt connections...initial PS pic here:
Recapped, installed all new square pin headers, new connector housings with trifurcons, new Texas Instruments LM723s, installed a new higher rated long leg BR1 sat a little higher off the board and added a heatsink(through hole plating was perfect, but still I still solder both sides, burnished and deoxited fuse clips(left -5 reg and R10 unpopulated to test....NEC 7905 voltage unloaded was crazy different than the original, +5V voltage unloaded was 5.2, a little high with R10 clipped)
New housing with trifucons on heat sink transistors...fresh transistors installed(2n6059 and an On Semi 2n3055 I like to use in my rebuilds)
Replaced the -5v NEC 7905 regulator with an On Semi part which regulates unloaded like the original part did(-4.97v unloaded at PS, loaded at the MPU board it was -5.01, perfect)...reinstalled R10(51k) and my unloaded voltage at the power supply was now 5.1...voltage loaded at the lowest ram on the MPU board was +5.01 volts...perfect!

Game booted right up no errors! Clean power, perfect voltages