[Amps] SB-220 filament problem

[Keith Hamilton]

I have a SB-220 I got from the e place. Unfortunately its not
working (go figure!) The filaments of the tubes will not light.
I have another set of 3-500s and tried swapping them with no
luck. I do have lights on my meters and they light ok. I see
from the schematic that the lights are on the same circuit
coming from the filament transformer.

Well now I am stuck. I am not familiar enough with high voltage
amps to be poking around to much. Is there something else I can
check easily or should I start looking for a new filament
transformer?

Thanks for any help!  Keith W8GX