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Thread ID: 98857	2009-04-10 08:17:00	Electronics question: Parallel backlight inverters	george12 (7)	PC World Chat

Post ID	Timestamp	Content	User
763794	2009-04-10 09:32:00	unmodified inverters in series that or find the base/gate of the main driver and cut the base/gate on the other one and solder a wire from the unmoded one to the base/gate of the one with the cut base/gate line. the base/gate line should be the thin track on the driver transistor/mosfet the other two being drain source or collector emitter I actually cut the collector and and linked it, because the transistor used is quite capable of running both! Bridging the capacitor as suggested by you was much, much more effective though.	george12 (7)
763795	2009-04-10 09:33:00	ok, im not sure but higher values will possibly work. failing that try lower values make sure they can handle the voltage (at least 1Kv)	williamF (115)
763796	2009-04-10 09:39:00	ok, im not sure but higher values will possibly work. failing that try lower values make sure they can handle the voltage (at least 1Kv) It seems to be 0.06nF according to my meter. However the meter claims the air is 0.02nF.... I'll have a look at work tomorrow (working at Jaycar makes this stuff rather convenient!) and try a few higher and lower. What type of capacitor would it be? It's blue and kinda lumpy looking... Thanks heaps for your help.	george12 (7)
763797	2009-04-10 09:46:00	assuming your fingers werent contacting the pins or testing leads the cap value is probably 0.04nF or 40pF has it got a number printed on it eg 40, 400 or similar and perhaps a picture and try the resistance range try a 1nF, 10nF and 20pF	williamF (115)
763798	2009-04-10 09:50:00	Ah, I missed the number on the other side. It says 22 (just 22), and 3kV. So is it 22pF? I can only find a 10pF 3kV ceramic cap on the awful Jaycar website so I may try that. Otherwise could I perhaps use a resistor?	george12 (7)
763799	2009-04-10 09:52:00	Ah, I missed the number on the other side. It says 22 (just 22), and 3kV. So is it 22pF? yep make sure the caps you get can handle ~2.5 - 3 kV	williamF (115)
763800	2009-04-10 10:00:00	yep make sure the caps you get can handle ~2.5 - 3 kV Hmm OK. That 10pF one might be the only high voltage one they have, in which case can I use a resistor? Final question, how do I know if 12 watts inverter draw per tube is too much or not? For all I know that may be the intended brightness...	george12 (7)
763801	2009-04-10 10:08:00	the flouro lamps possibly actually run at <1000 volts so a lower voltage rating could be used for continuous. resistors on high voltages not only is inefficient they can also become a fire hazard, capacitors produce less or no heat while still acting like a resistor on AC/pulsing DC if you do use resistors use ~15k - 150k or higher and at least 1 watt and bypass the capacitor with it	williamF (115)
763802	2009-04-10 10:16:00	the flouro lamps possibly actually run at <1000 volts so a lower voltage rating could be used for continuous. resistors on high voltages not only is inefficient they can also become a fire hazard, capacitors produce less or no heat while still acting like a resistor on AC/pulsing DC if you do use resistors use ~15k - 150k or higher and at least 1 watt and bypass the capacitor with it Ah, I suspected as much, thanks. Won't be using a resistor. If I get stuck I can always use several of those capacitors in parallel and/or series I suppose. But how do I tell how much power the tubes should be getting?	george12 (7)
763803	2009-04-10 10:48:00	its hard to tell, but the tubes should be fine if a little overdriven its hard to blow cold cathode tubes with too much voltage, the high voltage is mainly to strike the arc and the lamp pulls the voltage down to a few hundred volts and the inverters cant supply more than what is put into them so most flouro tubes should be fine with whatever is applied to the terminals	williamF (115)
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