So I recently re-capped my SE/30 analog board, but the focus control isn't working. Cutoff does work just fine. I have searched the forums and TomLee and trag mentioned R26 as the issue. In addition to that TomLee says this:

"If the cutoff adjustment works, and given that you have verified that the focus control has no effect, the problem is either a bad 1M resistor (the previously-mentioned R26), or a poor connection between the focus control wiper and the CRT focus electrode. Verify that there's continuity between the wiper and J2-9"

What is a focus control wiper??

Also, can I test R26 right on the board, or do I have to remove it first? Or just replace it, because it's probably a cheap part?

Thanks very much for any info.