On 5/4/2012 10:24 AM, bud-- wrote:
On 5/3/2012 2:24 PM, dpb wrote:
....

Have you actually taken the ground connection loose and checked it or
simply looked at it? Just because it looks good on the surface doesn't
mean there's not a resistance layer between the mating surfaces or a
layer of paint or whatever.
....

A grounded surface near the lamps is used to start the tubes. As far as
I know a ground is not needed for the tube operation once the tube has
started. Sounds like all the tubes are operating (but not bright enough).


I don't remember that the OP has verified that the sockets make good
contact with the pins and that the wires make good contact with the
sockets (for instance that the socket doesn't 'contact' insulation
instead of wire).

As I wrote previously, a darkened end likely indicates that the filament
at that end is not working (burned out or not receiving power).


True, but that ground reference is to the power ground.

Just as OP hasn't indicated that he has really verified any of the
suggestions made by anybody he hasn't indicated just what other than
replace the ballast and reinstall the light he's actually done to ensure
all the possible areas of poor connections whether in supply, grounds or
sockets/pins have been addressed.

I agree it's almost got to be one (or more) poor connection(s)
somewhere; it seems highly unlikely that the ballast itself is the
problem given that a new one and old one behave the same.

--