In article , O.B. wrote:
We have a 4-lamp magnetic ballast that is on the blink. The ballast is a Mark
III Energy Saver made by Advance Transformer, catalog number R-4S40-A-TP-AC.

This ballast is a magnetic ballast and costs $60 to replace. I can be a
4-lamp electronic ballast from Lowe's for $30.

Is it possible to swap the bad magnetic ballast with an electronic
ballast? If so, are there any modifications that I need to make to the
4' fixture?

1. The wiring may be different - look at the wiring diagram on the
ballast label.

2. Check the ballast label and the lamps to be sure they are compatible
with each other.

If you are doing a ballast relacement with an electronic ballast, I
would get one for F32T8 (4-foot) or F17T8 (2-foot) (T8 is one inch in
diameter) lamps rather than F20 and F40 (T12, or 1.5 inch diameter) types.
T8 lamps are mostly a little better and usually have higer color rendering
index. Ballasts for T8 are usually better than ballasts for T12 so far in
my experience.
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If you are in for new lamps (bulbs):
My favorite T8 lamps have color codes SPX35 or 835. This is (in my
words) "semi warm white". 30 is warmer and 41 is "cool white color". SPX
or 8 (followed by the 2-digit abbreviated color temperature) means a color
rendering index of 82-86, with most of the color distortions in the
direction of making colors more vivid than "proper". SP or 7 followed by
2-digit abbreviated color temp. has a color rendering index in the upper
70's.
I would not bother with fluorescents with CRI 90-plus - they cost more,
have less light output, and their color distortions, although slight, are
mostly in the direction of making colors duller than "proper".

- Don Klipstein )