all help appreciated....

instrument warning lights all work, stop, oddo, indicators,  lights
on, main beam  etc, but no basic illumination.

all lighting controls work, headlamp on warning light sound etc.

Have checked all bulbs, four bulbs in central positions (behind the
dials) test ok elsewhere but do not illuminate in situ.

I've by-passed the dashboard dimmer rotary switch, still no
illumination.

You're may last hope...

Thanks in advance