Hi: I just had the same problem with my Intercom system / what i did was get 4 seperate caps at radio shack as they are all common ground. Just make sure you install the caps in the correct location as it is marked on the outside of the capicator. and make sure you connect the grounds to all 4 post on the circuit board. I installed the caps upright in the same location as the can capicator was in. also there was another cap bad the value of it was 100mfd/15v its a single cap located close to the multi can capicator noted above. hope this works out for you have a good one