If you are using a known working AV lead, TV, power supply, and have bridged the B34-35 pins together, get the power LED turn on, and you still get nothing at all (audio or video) then common culprits include:

• Bad BIOS (check BIOS Boot for confirming BIOS is working firstly)
• U23/U24/U33/U34 (Work RAM)
• Bad Lower Expansion Address or Data buffers (U30, U31, U26)
• Bad Crystals
• Short Circuit
• Bad AV Circuit (see Video Output section)
• U29 (68k CPU)
• U15 (Jerry) or U13 (Tom)
• Trace damage on board between Tom/Jerry/RAM/BIOS/Buffers/AV circuit
• Short on any of the above ICs or bridges between pins
• Bad capacitors causing shorts

If you have an oscilloscope you can check out lots more on the circuit first like BIOS Boot and Video Output section.

Audio But No Video or Game Load

If you hear the Jaguar roar on boot, but never the game loading, and you know the Video Output circuit is good, and your AV lead, if the address pin A18 (going to U14 input 1A3, and Jerry pin 118 and so on) is bad, it can cause black screen and failed load, but still the roar on boot.