If there is a tape record out, this is tied directly to the other inputs. Select an input (say, CD). Take a DMM and place one probe in the left CD input and the other in the left tape out. There should be a resistance of 1k to 5k. If there is a short, then the rest won’t work.
Take a cheap pair of RCA cables and plug them into the tape record out jacks. On each of the other end RCA plugs, solder a 10K trim pot, pin 1 to the inner positive and pins 2 and 3 to the outer ground. Adjust the trim pots for any volume you want and then hide the end plugs so the tenant can’t see.
What this is effectively doing is acting like a shunting volume control.
Take a cheap pair of RCA cables and plug them into the tape record out jacks. On each of the other end RCA plugs, solder a 10K trim pot, pin 1 to the inner positive and pins 2 and 3 to the outer ground. Adjust the trim pots for any volume you want and then hide the end plugs so the tenant can’t see.
What this is effectively doing is acting like a shunting volume control.