Maurice, because you mention the pcb connectors and supply voltages i assume you have seen the inside of (this) tv before and are confident working on tv's.
The 140V is only present when the BV3 comes out of standby, otherwise it is around 8V which is there because you have the red light.
An easy start can be unplugging the tv (from the mains) and than do an Ohm-mesurement on the +140V line you mentioned, to check for any short circuits.(leave the connection between supply and defl pcb connected !!, only interrupt the +140V line)
Another test is to desolder a component on the deflection board which makes the +140V go to the HT transformer, so you actually disconnect the +B supply to the HT transformer.
And than you connect a bulb of 40Watts to the +140V (temp solder onto the quite big capacitor for the +140V based on the supply board).
If you try to switch on the tv now the bulb should glow (and you should be able to measure around 140V).
In this way you can already determine if the supply is the problem or the deflection board.
I have to be honest in saying i did this on an Avant RF which basically has the same chassis as the BV3 but i'm not totally sure if this should work on the BV3 (nevertheless worth a try.....at least if the bulb lights at 140V you can quite safely assume the supply is ok, but if it doesn't it may therefore not necessarily mean the supply is defective).