The game plays but has no sound. At power-on there may be a burning smell from the sound board, with scorched diodes in one corner.

No sound and a burning smell from the sound board: diodes, then the board

Cause: The four diodes on the sound board form a bridge rectifier for the negative supply used by the DAC chip. They run hot and can fail from heat stress. If sound is still missing after they are replaced, the fault is elsewhere on the sound board, often its obsolete custom processor chips.

Checks

• Test the speaker on its own (ohm it out or try a test speaker); speakers on these games fail often.
• Check the volume pot wiring and the +5 V and +12 V supplies at the board.
• Replace the burnt diodes (1N4004 or 1N4007) and check the large filter cap near them for leakage.
• If still silent, look for digital activity on the lines feeding the DAC chip when a sound should play: none means the processor side, activity with no sound means the amplifier side.

Fix

• Replace the bridge diodes first.
• If there is still no sound, swap in a known good System 80 sound-only board, moving this game's sound ROM onto it, or fit a modern replacement board.

Systems

• Gottlieb System 80

Games

• Panthera

Related tips

• Some or all sounds missing
• Replace C33 on the speech and sound board
• Sound aux supply keeps blowing its 2N6059: shorted capacitor on the 30 V rail
• The System 80 sound board generations by game number
• Haunted House and Black Hole sound board DIP switches
• Sound supply fuse F8 blows after the game runs a while
• Haunted House: no sound 16 in the sound test
• The wrong sounds or tunes play

Source: Pinball Repair help group!! (Facebook group)