AndrewF

Thank you @Scorp007 you had the answer I needed.

I also removed TX7 to check it...using a desoldering technique shown on You Tube where a thick 2.5mm dia piece of solid core copper wire is wrapped around All the pins in a row then with powerful Iron and added solder, the whole area is heated up to release the soldering of one side of the transformer, the transformer is then simply pulled loose carefully and same procedure is repeated on opposite side still soldered to board....the result was a perfect unsoldering of TX7...The last time I tried similar thing I destroyed tracks and pads so went looking for ideas...

Hi would it be possible to isolate the DC to DC SMPS converter mosfet gate pulses so that there's no switching on DC to DC converter and therefore no BUS voltage and then do test method injecting RasbPI signals into IGBT inverter circuit.
So use the inverters SMPS to power all circuits instead of using external power supply to power up as described in  journey of repairs....., the only external power supply would be the 25v - 150v DC injected into the BUS to confirm that IGBTs are working OK..
Just a thought.....

I use Stainless Steel(solder can't/won't tin SSteel) Electric fence wire holding solder iron on opposite side of pad to to heat up solder then push through towards the solder iron. Works very well, after struggling as much with "solder balls" jammed inside pads/vias....

Thanks that makes total logical sense now, As QB has sine wave But QA doesn't have , need to trace where that opposite cycle wave has gone missing  !!

I'm looking for waveform screenshots on input pins on all optos driving the Inverter IGBTs if anyone has captured them for reference.. some of the waveforms on this board seem unhealthy/not good..
 
 
Many thanks to Coulomb and  BritishRacingGreen for your valuable input shared above ..... this Will No Doubt help many members going forward with this valuable topic....
 
so somehow i selected the incorrect reply box , LOL , anyway . the last issue was -12V pulled down by......, i found a damaged TL074 as well as 16V Zener short circuited(removed both), for IGBT gate driver, and -12V is back(whew, relief.....) not sure which one caused it . I forgot to check -12V before and after these 2 discoveries .. but getting there it seems, will get replacements and start looking(scoping) for sine wave and switching waves respectfully..