Hi Jeff - Yep your 109 is putting out some power! But it was designed to drive a higher impedance antenna like the 100' "hank" wire provided. With a lower impedance antenna like a dipole / 50 Ω or lower, the lamp can be over voltaged and eventually fail. Carry spares...
If you want to routinely use a low impedance antenna you could change R-13 to a lower value or shunt it as Chris suggested. But then later with a higher impedance antenna you might not get enough glow to properly tune the TX.
I put a 12 ohm 2W resistor in mine vs the 20 Ω, works fine. The RS-6 transmitters have the same issue but with a different lamp. I also reduced the shunt resistor in mine as well. It's a tradeoff when not used "by the book".
When running the system off a nominal 120 VAC source setting the PS selector to 130 Volts is correct.
Everything I have learned about the GRC-109 and field ops here if interested:
Have fun with it - It's my Daily (OK weekly) Driver... I just had mine out for Winter Field Day - works great.
Tim
N6CC