1) Make sure your power supply is fully working as well. PCE uses the same as a Genesis Model 1.
2) Try turning on the unit, and flip up and down through those channels in the 90s that others mentioned above, sometimes the signal will not work when first powered on, but if you turn it on then move off the channel and back onto it.
3) Try running it through a VCR or on another CRT.
I would seriously just region mod the sucker, or make one of those with the leads off the EXT