Sparton 16A211 Width Problem

[teevee]

From your earlier, you had stated that the drive waveform (W18) was per the schematic (120V p/p) If so, it would be worth scoping the cathodes of the 6BG6's. (Just to confirm that C131 is doing it's job.) Also, it's interesting that the schematic is showing these freq's as 7875 cps, rather than 15,750. Maybe that's a ref to showing 2 cycles on the scope? Yes, the "capacitor across the damper" trick will increase width some, BUT will result in lower HV, boost, etc.