http://i284.photobucket.com/albums/ll33/bonosurf/470Lamp.jpg
I am working on a 470 and have run across a simple lamp driver circuit issue which is driving me mad. The B channel lamp will not operate when the switch is put in the B channel mode. I have checked both bulbs, replaced Q211/210, resoldered every possible node.
It looks like the drive transistors get the correct base bias voltages but the collector on Q210 reads 26V instead of 33 in the B channel mode and Q211 collector is at .7V instead of .3V in the B channel mode. I'm stumped by this very simple circuit.
I am working on a 470 and have run across a simple lamp driver circuit issue which is driving me mad. The B channel lamp will not operate when the switch is put in the B channel mode. I have checked both bulbs, replaced Q211/210, resoldered every possible node.
It looks like the drive transistors get the correct base bias voltages but the collector on Q210 reads 26V instead of 33 in the B channel mode and Q211 collector is at .7V instead of .3V in the B channel mode. I'm stumped by this very simple circuit.