Wurlitzers tend to rotate the keyboards up out of the way, but that was in 1966, haven't worked on a 1978 model. If the dc voltage to the keyer IC does go up & down from the 'bad keys' just like the good keys, then either the keyer IC is bad, or else as I said in the beginning, faulty power supplies are just bad enough to make one IC not work but the other ones do. You need an alligator clip lead for the negative probe anyway to nail that to analog ground. Available from newark, mouser, digikey, Fry's, etc. It is best to use a Pamona 'dip clip' and a pamona 'grabber' to check actual leads on the IC. It is best to check dc voltage on leaded parts (like resistors) that go to the IC instead of touching the IC itself. You can prove or disprove this theory with a voltmeter.
Some of them may not work, Ie the Dc voltage may be in the 'note on' state all the time. Some of them work, ie the DC voltage comes and goes as you put the key down and let it up. If there are keying IC's, then probably DC voltage comes from the keys to the gate controls.
You can check the key contacts with a voltmeter, instead of taking everything apart first.
