Either me or wayout440 , but someone is mistaken (I think I'm right). but according to the manual , Twilight Zone doesn't use the soundboard with the TDA2030 dual amps, but uses the much more common board with the single amp LM1875. You are also experiencing the same symptoms as if you have a single amp. If you unplug the cabinet speaker, you are effectively taking both speakers out of the circuit. I see only 2 ways this can happen. The speaker itself has its coil shorted or it's cone popped out. If you have a multimeter , unplug the cabinet speaker and measure resistance, how much is it ? It should typically be 4 ohms. If you measure the 4 ohms ,the cones must be broken. If you measure less than 4 ohms the coil is most likely shorted. You can use a 9v battery to basically test a speaker and see if the cone moves. Disconnect both leads of the speaker before you use a 9v battery. Just briefly touch the contacts to the battery, if the cone moves the speaker *should* be ok. Don't do this test too much to be sure you don't damage the wires connecting to the coil of the speaker.

I think wayout440 looked at the wrong sound board schematic in the WPC Schematic manual, as the board with the dual amplifiers is shown in there , but that's not the one used in Twilight Zone.

The speaker wiring I took from the fish tales manual , as it is missing from the TZ manual.

speak (resized).png