Repair Yaesu FT901 DM suggestions/recommendations

[LFibich]

 Looking for repair /suggestions as to what area and/or components to look at.  I had a unit with a bad transformer and it burned - met a person on line and he offered a chassis with a good transformer that had been cannibalized for the boards and removable components - I don't know what it was cannibalized - but the unit and wiring really pristine... so I used ALL the boards and removable components from the unit I had - checked them before and again when assembled in this 'new' unit -- I have another unit that works - and ALL boards worked fine.  OK when completed the 'new' unit display blinked and nothing worked -- traced the difficulty to a voltage regulator transistor and replaced it -- Unit works PERFECTLY on receive; and perfectly on AM; CW; and FSK - BUT no power output on SSB (upper and lower); and FM.  Studying the schematic I thought surely the diodes on/around the mode switch (that appear intimately involved in SSB) would be the cause -- checked all (6) and they are fine.  Also 3 other diodes wired on the board connectors - ok but not really involved.  ON SSB section - audio monitoring works, relay's click/work; vox works - all appears OK except no power out put and of course minimal IC..   Looking for suggestions as to where to look/check...  Since ALL the boards work and removable components HAS to be something on the chassis - perhaps the reason it was cannibalized in the beginning???  Any and all suggestions most appreciated... 73  Larry LFibich@sbcglobal.net W6EF

[m3vuv]

does it get any drive to the 12by7 driver valve?

[bob91343]

Break out the oscilloscope and track the signal, as hinted by the above post.