is it okay to run MV lamp base down. I know on SOX lamps you shouldn't run them Base Down.

It is ok to run a MV lamp base down, but not probe-start MH lamp.

It is ok to run a MV lamp base down, but not probe-start MH lamp.

thank you for the information.

It is ok to run a MV lamp base down, but not probe-start MH lamp.

Not always, you're better off checking the suffix in the lamp model number. I've listed the typical ones below. Most probe start lamps are actually rated for universal burn.

/U - Universal burn, IE any position
/V - base up or down with 15 degrees of vertical.
/BU - base up only within 15 degrees of vertical.
/BD - base down only with 15 degrees of vertical.
/HOR - horizontal burn only, requires a special mogul socket.

It depends on the individual design of lamp. Some lamps of most types (except LPS) are universal burning, some demand specific positions, this is usually marked on the packaging or the lamp etch. It is by no means a universal statement that lamp X must be run base up or lamp Y base down, or whatever.

For standard MBF lamps it is universal statement - They are made for any burning position. However, in the vertical cap down position there is some chance of the Mercury eventually shorting out the probe, in whcih case the lamp won't start. This is then repairable by unscrewing the lamp and giving it some shaking