Bush VHF90

[Yorkie]

This is curious as the Bush data sheet I downloaded says the lamp shunt resistor is 30Ω. I'll be interested to see what's actually fitted.

- Joe

Of course the lower the value of the shunt resistor, the more current that will flow through it. and the less current will flow though the bulbs, thus conserving their life. Maybe Bush realised this at some stage, so lowered the value of the shunt to 30R? If you check the voltage dropped across the shunt, when you check the actual resistance you'll be able to discover the current flowing though the resistor (I = V/R), and from that, the correct wattage (W = I x V).

If a shunt resistor goes high due to aging, that will mean that less current will flow through the resistor, and more will flow though the bulbs, putting them at risk. If for the sake of example, a 30R shunt resistor drops 10V, (I'm not saying it does drop 10V in the VHF90), the current flowing through the resistor would be 333mA. If that resistor went high - say 50R, it would then only pass 200mA, so that would place a higher load on the bulbs.

Best of luck with it Joe - do keep us posted!

David