Furrion DV1230-BL Radio/dvd player has 3 zones, I was trying I determine why the set of speakers on zone 3 could hardly be heard with the volume all.the way up, I swapped the wires with zone 2 and they worked just fine, I determined the radio had a faulty zone 3 and was defective, I ordered a replacement and the new one has the same issue-- so I simply swapped the speakers to zone 2 and put the soundbar on zone 3 since the soundbar has a volume control which seems to work ok, long story short I'm looking for some type of meter or piece of test equipment to measure audio output to determine if the problem is actually with the radio, any ideas on what test equipment I would need?