21fb j p22

[timmy]

I have a spare 21fb and testing it on 2 different bk440 testers shows the red gun is weak but when I check the tube in the moto it shows all 3 guns are good on the 440 testers but I have a bk tester from 1978 and both tubes show good all 3 guns I don’t get why the newer bk shows the tube with the weak red gun as good. I know 2 different testers but all work fine it’s odd. Which one do I believe.