Drilling a solder filled feedthru can cause the inner plane connection(s) to be lost if the drill removes the feedthru barrel. So if you have really tiny drills, accurately centered, ok. Better to suck it out with a antistatic solder sucker, solder braid, or melt it and punch thru with a stainless steel wire that the solder will not wet. However in this case I think there are other grounds and you will be ok. That feedthru probably went to the inner ground plane and probably did not ground any inner layer traces.
C5 positve bypasses two sound chip voltage reference pins to ground. So the positive end of C5 connects to UB10-15 and UB11-15. Once the pad is gone or even lifted, that really skinny trace is the devil to connect to even with the finest copper wire (flexible power cord is a source for fine bare wire).
C6 positive goes to UB11-7, a sound chip pinout that needs a 1 uf bypass to ground.
C4 positive goes to UB11-10. This is the right channel sound output on its way thru the blocking capacitor C4 , series resistor R12, EMC supressor L2 out to the phone jack J1.
I have had some success resecuring lifted pads with 5 minute quick setting epoxy. But when you hit a freshly glued pad with the hot iron, who knows what the chemicals emitted will do to you, so have some good cross ventilation going. Soldering first then sticking down the pad might be better if the arrangement of things allows this. Clean the board and pad surfaces with denatured alcohol before gluing. If the pad is corroded away you can make a new pad from copper foil or even a smashed down bare wire, epoxy it in place and then you have a somewhat secure place to anchor the replacement part. But when at solder temperature, both the epoxy glue and the epoxy in the PC board is practically liquid under the pad, so a gentle touch with the iron is necessary. No harm in applying a bit more epoxy after the soldering is complete if necessary.
C5 positve bypasses two sound chip voltage reference pins to ground. So the positive end of C5 connects to UB10-15 and UB11-15. Once the pad is gone or even lifted, that really skinny trace is the devil to connect to even with the finest copper wire (flexible power cord is a source for fine bare wire).
C6 positive goes to UB11-7, a sound chip pinout that needs a 1 uf bypass to ground.
C4 positive goes to UB11-10. This is the right channel sound output on its way thru the blocking capacitor C4 , series resistor R12, EMC supressor L2 out to the phone jack J1.
I have had some success resecuring lifted pads with 5 minute quick setting epoxy. But when you hit a freshly glued pad with the hot iron, who knows what the chemicals emitted will do to you, so have some good cross ventilation going. Soldering first then sticking down the pad might be better if the arrangement of things allows this. Clean the board and pad surfaces with denatured alcohol before gluing. If the pad is corroded away you can make a new pad from copper foil or even a smashed down bare wire, epoxy it in place and then you have a somewhat secure place to anchor the replacement part. But when at solder temperature, both the epoxy glue and the epoxy in the PC board is practically liquid under the pad, so a gentle touch with the iron is necessary. No harm in applying a bit more epoxy after the soldering is complete if necessary.