main burner on apollo 65/50 b won't ignite?

When the sensor gets hot enough from the pilot flame the control board opens the main gas valve.

You may have a weak pilot flame from a partially blocked injector - a defective sensor - a defective control board - a defective gas valve. You should be able, if you have a multimeter, to check for voltage being sent to the main gas valve. Any sensible sevice engineer would make this check first - it's quick, easy and costs nothing. He would then work backwards from there.

I an not quailified and have no experience - my advice is worthless.

Good luck...

Peccavi
March 2010