Fluorescent Lamp Inverter 12 volts

[barry wilkins]

The lamp inverters failed in my caravan ,a couple of 2A transistors had died.After cleaning up the mess and replacing them with a couple of BD 139 transistors ,the inverters would not run when I connected up to my bench power supply .The current was over 3 Amps and the psu shut down . I traced the reason to the 2 bias resistors of 470 ohms ,increasing the value of these to 1K or even more made a big difference to the current drawn . The only reason I can assume for the design is to ensure the lamps would strike if the supply voltage had dropped below 12 volts .
One inverter has bias resistors of 1K and the other has 4.7K fitted ,both seem able to work as low as 10 volts ,so I will see how they behave if the future .

Barry Wilkins

[Th3_uN1Qu3]

Re: Fluorescent Lamp Inverter 12 volts

I think the original transistors had lower gain hence higher bias current.

[kc8adu]

Re: Fluorescent Lamp Inverter 12 volts

often they are house marked and hand selected.thinlite does this.i dont have too much trouble fixing them.

I think the original transistors had lower gain hence higher bias current.