Sir bushtech . . . . . . .
On that MELF profile diode that you pulled , do a Vf "diode" test on it, vice the ohms test that was resulting in its giving a 30 ohms forward reading.
Then see if its reading in the 0.500---0.700 VDC range, as would be expected on a good silicon diode junction...
THEN to see it it has a Zener action, series clip two 9VDC batteries M & F connectors together for a resultant 18VDC , a series 1500 through 2200 ohm current limiting resistor clip leads to the + battery connector.
Then the tested diode has its cathode/band going to the free end of that resistor while its anode lead goes to the battery negative connector.
Then you DC meter across the tested diode, with your third and fourth hands, and expect ~9 or ~ 3VDC if they are using a Z diode for the acquisition of the sub power supplies.
If it reads on up in the 18VDC range , then you have no zener action in the range we would expect to find being used. . . . . assuming it to then be a common silicon diode.
So THEN you go back to your good working unit and measure across that equivalent diode on its board and get its DC voltage reading across it.
73's de Edd