Inaccessible filter caps - draining query

[Steve Blackdog]

So you mean zero Volt at "HT PS"? If so, you have no PI and preamp supply. Check if R203 is open. Do the EL34s have screen voltage?

Why don't you post the complete schematic?
Not even clear what brand and model this amp is.

So tested voltage at plates: 559 on both.

new problem- switched on channel 2/od puff of smoke and the HT fuse blew. The od switch goes straight into the IC10, which is a programmed PIC16f57, and not obtainable. Hope that hasn’t gone.