I'm working on an upgrade modification for this GFP-750 preamp. Once the cap portion of the upgrade was installed, I noticed I had no right channel when the unit was out of passive mode. I've checked components, traces, solder joints, and voltages. Some of the voltages are off on the right channel, but I can't figure out what is causing them to be off. Any help would be appreciated.
That's not easy to follow 🙂
What do the red crosses mean? If it means no voltage then...
You seem to show 60v on parts that are close to the ground point. Are you sure you are measuring form the correct ground point?
What do the red crosses mean? If it means no voltage then...
You seem to show 60v on parts that are close to the ground point. Are you sure you are measuring form the correct ground point?
Sorry about that. Stars mean voltages look good. I measured the other channel with the same ground point, and everything checked out.
Right then... your missing a ground connection on the board by the looks of it. That line at the bottom should be zero volts. The fact you have 60 volts pretty much everywhere suggests its floating (not connected).
You're right. The two grounds (in blue)
that both sides share are not showing continuity. The left channel is.