[BillDWVA]

Hi,
You have identified the capacitor most likely to cause trouble; namely C19, which couples the anode of V3 (pre-amplifier stage) to the control grid of the output pentode via what looks like R22 (sorry the image is a bit blurred). Another one to check, and possibly replace on sight, is C20 the coupling capacitor from V2, in the previous stage. Modern axial polyester capacitors are OK as replacements and are not expensive.

These capacitors have a high DC voltage stress across them and if they become leaky affect the biasing of the following valve. At best causing distortion and at worse, damaging the associated valve.

Going back to a previous post regarding the screws holding the components to the deck plate; these are plated, domed, countersunk cross-headed and may be difficult to source replacements for. I have only been able to find plain steel screws in BA sizes when looking for new. If you need spares then Terry Martini-Yates at Ferrograph World is your best source of parts for these decks.

Hope this helps?
Bill