Q: Ebay fluorescent ballast

[wilfred]

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[Zero999]

If it's not as bright, it's possible the ballast isn't really outputting 32W into the tube - the power output of cheap ballasts is often overstated. An electronic ballast should theoretically give a brighter light, for the same power output.

In nay case, I wouldn't recommend a florescent for intermittent operation, since it takes awhile to warm up and achieve full brightness.

EDIT;
If you keep the heaters permanently powered with a small twin 6V secondary transformer and the tube will start instantly but you need to consider the standby power consumption will be high.

[Gazucha]

 Hi,

 I'm not quite sure why you wanna buy what must be a common-type ballast from China but providing the tube is happy, a 32W ballast for a 20W tube should certainly give you more reliability (and light) than your 21W.

  Personally wouldn't  recommend going to a much higher wattage than 32W though (30% more), as you may damage the tube when starting up with the larger coil if you went to say 40W.
 For example if I am changing a 4ft 40W choke (ballast), I won't go buying a 75W - 80W choke (50% more).
 
 That said, for 7 bucks, the worst that can happen is you need to find a more powerful tube (or a slightly lower wattage choke), and you'll have learned where the limit lies with choke to tube-wattage ratio.