Here is what I have been able to deduce / theorize what is happening.
1. The flyback transformer has secondary windings on it that are also used to supply +15 and +25 volt dc source via rectifier diodes D514 and D508.
2. Checking the +15 volt supply confirms it is working.
3. Checking the +25 volt supply indicates it is NOT working.
4. D514 test good.
5. Resistance from pin 11 to pin 6 of the FBT indicates very low resistance as expected.
6. Resistance from pin 11 to pin 8 of the FBT indicates about 11 Meg and indicates an open winding on the FBT and this is what supplies the 24 volt supply.
Conclusion... I doubt a FBT could be found and I have a 1983 curb prop.
Let me know what you think
.
Steve