CMH with switchable ballast. HELP!

I use a 400W CMH on a magnetic HPS ballast and I love it. So i bought a 250W CMH for a Sun Systems switchalbe 250W builit-in ballast. However it will not fire. I got this from a friend and do not know about the ballast other than I have 250W HPS and MH lights that both work in it. If a 250W HPS works in the ballast, shouldnt a 250W CMH? Is there anyway I can trick the ballast into thinking the HPS is plugged in or am I having some other problem? THanks

And both bulbs are Phillups Mastercolor CMH.

n dubbya

i need to get hte yellow out of the right side (250W HPS)

i have a 400 watt ballast that seems to have a similar issue. it fires up hps bulbs at ease. but it just doesn't like cmh. within a day or two, it fries the bulb or just won't fire it up. i asked in the cmh thread and everyone said to get a new ignitor. i recently got another 400 and 600 watt system so this isn't my #1 priority at the moment. i'm interested to find out if it worked for you tho. a new ignitor is pretty cheap. other than that, i have no idea

You cant put a CMH bulb in a switchable ballast, period.