OK, I suggest the following next steps...
1/ please visually inspect the area where you removed the flek... is there any chance the copper track is visibly bridging between pin 3 and pin 4? Another photo would help ifpossible please?
2/ with the 15V power supply completed disconnected, and with the four pin track power plug also removed please take five measurements with the meter set to the lowest resistance measurement setting. Please measure resistance between pins 1 and 2 - then again with the probes reversed. The please measure resistance between pins 4 and 3 - then again with the probe pins reversed. Finally measure the resistance of the probe leads by touching the two probe tips together directly.
This data should help with final pin-pointing ofthe problem...
I still suspect the site of the flek of debris I am sure together we can get this powerbase back into full working order... which continent do you live in?
Ok, on the bad side. That the side closest to Q3, where I think I might see some heat distortion on the back side (pic coming)
I get a slow drop from 1 ohm to .6 regardless of which lead is on either pin.
On the good side, I get no resistance from pin to pin in either direction of lead placement.
Lead to lead I get .4 ohms. My meter (I'm using a cheap one because my good one is in my car, but it is functional) is set at the lowest setting of 200ohms.