[Premium-Rx] Cubic R3030

[Charles Steinmetz]

Reviewing the 3030/3080 schematics, I have to agree with the 
suggestions to remove or relocate CR12, the 430v MOV connected across 
the +/- outputs of the bridge rectifier.  Its only possible function 
there is to cause the bridge to fail.

There is one 430v MOV (CR14) directly across the AC line input, 
followed by a line filter, feeding the AC inputs of the offline 
rectifier bridge (CR13, which we have been discussing).  The DC 
output of the bridge has another 430v MOV (CR12) directly across it, 
and a pair of NTC thermistors ("surge protectors") feeding the 
offline filter capacitors, C20 and C22.  Putting an MOV directly 
across the bridge is just asking for trouble.

Either remove it (it is completely unnecessary), or move it in front 
of the rectifier bridge (electrically, in parallel with C21).  While 
you are at it, check both MOVs with an ohmmeter to make sure they are 
not leaky.

Best regards,

Charles