What I meant was, is it possible that there is a chassis ground built into the pt so it is grounded through a mounting bolt? See the ground symbol at the bottom of the pt windings in the schematic?
No, not like you mean.
The ground symbol you're talking about runs up to a dashed line running through the center of the PT symbol. That indicates an electrostatic shield; this is a shield that is placed between primary and secondary, helps reduce noise and parasitic components, and must be connected to ground. That shield cannot be connected to the PT secondary the way you guessed, because it would not perform its intended function.
When we think about "point-to-point" we sometimes think this means old Fender amps with an eyelet board and easy-to-follow wiring. In reality, it means "rat's nest" construction styles as typical in some Gibson, as well as Supro-related and many other old amps. The component leads generally form the connecting wiring, and tracing the circuit can be very difficult. There are ways to arrange parts that yield the correct electrical connections, but don't lend themselves to easily seeing what is connected where.
What is that little brown wire that we see above the 220 Ohm resistor attached to? And is that 220 Ohm resistor supposed to be 3.3K Ohm or a 130 Ohm resistor?
No clue on the brown wire. I'd need this amp in-hand to figure the wiring scheme.
You're on the right track, though. I don't see a 220 ohm resistor anywhere on the schematic. In the picture, I do see a 3.3k resistor (Orange-Orange_Red bands, thought the red is hard to see) connected to one of the filter cap positive leads.
I also see a short hunk of wire running from the PT CT and filter negative leads. It goes to one end of the 220 ohm resistor, and what may be a small cap.
As I said, there's no 220 ohm resistor on the schematic. It looks to me like with climbing wall voltages, someone decided to raise the value of the cathode bias resistor to tame output tube current.
Topic: Gibson GA-5T (Read 10582 times)