Need Help: Lynx II Q12 MOSFET gate pad ripped off

[EmOneGarand]

Hey all, I got my hands on a "broken" Lynx to see if I could repair it. It actually functioned just fine with batteries but the Power Connector had broken off inside. I soldered in a new connector so I could use an AC adapter to power it but that didn't work so I tried to replace the power circuit parts that typically fail. However while trying to remove the Q12 MOSFET which was being a real pain, I ripped off the pad for the Gate pin... Where does that Gate pin pad connect to? The schematic made it look like it was to R71 but I'm unsure, there is also a trace underneath where the stub that is the Drain pin is but I couldn't tell if that was connected while trying to remove the old one. Now it won't power on at all even with Battery power. Anybody else had this issue and been able to fix it?

[EmOneGarand]

What the damage looks like if that helps.

[+Stephen Moss]

The schematic I have also shows a connection to  R71, but it will of course also be connected to pins 6 & 8 of U6 and having visually check on my Lynx confirms that.

 

From the image it definitely looks like the Gate Pad has gone and so you have lost connection to both R71 and U6, the latter of which appears to connect to the underside of the PCB through the small Via pin between Q12 and D12 and then back to the top (component side) of the PCB through the small via to the left of pin 6 of U6. 

You should be able to remake the connection with a patch wire, use one end to make the Gate to R71 connection and solder the other directly to Pin 6 of U6

 

Visually the connection for the Drain pad look OK but it would be best to check the continuity with a multi-meter if you have one just to be sure.

 

[EmOneGarand]

42 minutes ago, Stephen Moss said:

The schematic I have also shows a connection to  R71, but it will of course also be connected to pins 6 & 8 of U6 and having visually check on my Lynx confirms that.

 

From the image it definitely looks like the Gate Pad has gone and so you have lost connection to both R71 and U6, the latter of which appears to connect to the underside of the PCB through the small Via pin between Q12 and D12 and then back to the top (component side) of the PCB through the small via to the left of pin 6 of U6. 

You should be able to remake the connection with a patch wire, use one end to make the Gate to R71 connection and solder the other directly to Pin 6 of U6

 

Visually the connection for the Drain pad look OK but it would be best to check the continuity with a multi-meter if you have one just to be sure.

 

Thanks a lot! That worked, got it working again under battery power.