I vote for a bad ballast. Get LED tubes and eliminate the ballast.

 

I ran into this same situation last week. Haven't had time to trouble-shoot it yet.

http://www.diychatroom.com/f18/how-troubleshoot-fluorescent-light-518178/
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Does the unit have a starter near one of the tubes.

 

There are no starters in the fixture.

 

I'm an electrician....it is almost positively a ballast

 

Connections were the first thing I checked. That is how I confirmed power.

Thanks Lanco, just ordered one from Amazon (big box did not have the model I needed).

 

When you replace it make sure you follow the diagram on the ballast and not the way it is wire now.

It may or may not be different.

 

The new ballast is the identical make and model to the current one so wiring is not a problem.

 

BEHOLD..., THERE BE LIGHT!!!

Replaced the ballast and it worked. I did not have to replace the bulbs.

I was curious about why there was voltage leaving the ballast but no light.

Before replacing the ballast I used my non-contact voltage tester to check for power along various parts of the fixture. There was power coming off the red leads at the ballast but oddly when I tried the tester near the terminals where the bulb plugs in, it alternated between not detecting voltage and briefly beeping. This leas me to suspect the ballast no longer had sufficient voltage to charge the lamps.

At any rate I got the ballast replaced and saved myself about $100 in the process.

 

You could have bought 4 LED direct wire tubes for less than $40, eliminated the ballast and never have to replace a tube or ballast again.
And used half the power in the future.

Sent from my RCT6203W46 using Tapatalk

 

I have had that fixture for over 15 years. Each bulb has only been changed once. This is the first time the ballast needed replacing and it only cost me $16.

If I ever put in LEDs, I will likely replace the whole fixture at that time.

 

To answer your original question, exactly, YES, bulbs can degrade at the same time. Face it, they are the same age. Often it is the ballast, though. When I worked at the Atlanta airport, one of our maintenance guys' job was to continually change fluorescent bulbs throughout the complex. He had a strict schedule as to when the bulbs were to be changed, and changed every bulb regardless of whether it was lit or not. Their theory was the bulbs were the same age and could conceivably burn out the day after he changed the one beside it. Hey, it was just money.

 

Thats just plain stupid and wasteful.
When I had many florescent fixtures, I always changed all the lamps in that particular fixture. The fixture I had open.

I would never open every fixture and replace every lamp in every fixture.
The only reason I replace all in one fixture is because I'm already working on that one and its open.
I would never touch a fixture that was working.