using the wrong bulb

im using an hps system that i got with a burnt bulb.
it is a 150 watt ballast and original bulb.

i had a few 70 watt hps bulbs laying around and screwed one in and it worked. and it seems to be working well..
is there any reason not to use it? could it burn out the bulb faster than normal? or overheat the ballast?

i maybe wrong but i think you can get away with a lower wattage bulb in a higher ballast because the bulb isnt drawing more juice than the ballast can put out, if you use a higher bulb in a lower ballast the bulb is pulling more than the ballast can supply and thats what causes overheat etc, but i wouldnt advise it either way, get a replacement 150w bulb

you sure its not a 70w ballast? that could be why it blew the 150w bulb and runs the 70 fine?

Watching this thread.

It is said that you can't do that, but from electronics I took 20 years ago I don't see why it would be an issue. Don't they all work on the same voltage and put out the same voltage? (talking magnetic ballasts here, digitals are another story probably)

Maybe the caps are beefier on the larger models for more current draw but a cap can only carry the voltage put across it, which I thought was the same regardless of wattage. Or maybe the bigger cap can put out too much current which would mean a simple cap change could make it run a smaller wattage bulb?

im not entirely sure mate, i know that i have read other threads in which people are using a higher wattage ballast with lower wattage lamps, im sure i read one where this guy was running a 400w ballast with a 250w lamp just for the summer grows and a 400w lamp for the rest of the year and no problems, but still i wouldnt wana try it, hid lights in my opinion shoudnt be mismatched or messed with in any way, especially not if your growing in your home. isnt it just the cap thats different between the wattages? arent the ignitor and coil and whatever else the same in all ballasts?

yea. the voltage stays the same whatever the draw of current or wattage of bulb, the voltage will stay the same on any electrical appliance unless that appliance uses a tranny to raise or lower the voltage??