What EXACT size are the bulb?

The diameter and length, and how many pins on the end.

With that information you should be able to get a replacement ballasts, but you may need to go to an actual electric supply house.

Two bulbs are 4 foot T8 with 2 pins and on is a 3 foot T8 2 pins. I assume all T8's are the same dimension-wise. I'll check into that. I know Home Depot doesn't carry these ballasts. They're very slim. I took pics but can't upload them from my store.

finding a two bulb t8 ballast is not hard, but you are going to need to make sure there is one ballast for the pair of 48 inch T8 bulbs, an another ballast for the single 36 inch T8.

If the three bulbs are on a single ballast it gets tougher.
The length of a florescent bulb plays directly with the striking voltage the ballast must develop.

Thanks. One clarification, though. Each of the 4' bulbs has its own fixture. There are three shelves. Top shelf has a 3' bulb, second shelf has a 4' bulb, and bottom shelf has a 4' bulb. Each fixture has a very thin black ballast that's maybe 8 inches long. So I'd have to buy three of them and hope that fixes whatever is wrong.

I have not seen a single bulb T* ballast in a while.

Duals and quads are the most common.

You may well have to go to an electrical supply house, or try searching online.

If none of them are working, make sure they have input power.
It would be odd for all three to have failed unless the input voltage is (or was) wrong.

A failed on-off switch could easily be the problem.

Thanks brickeyee. I know at least one has power because the lamp glows slightly, and I saw a little spark when I reconnected the fixture. I'll see if I can measure any voltage on each of the inputs. I can readily get the ballast from the manufacturer, it's just that I didn't want to buy 3 new ones if that wasn't going to fix the problem. They weren't even sure which ballast came in the deli case, but I'll send them a photo and hopefully they can order them.

Ballast replacement has always been the PITA of using florescent lights.

There are a few sizes/types that have become common enough to have at least some competition to help hold down prices, but like any replacement part they cost more than they did the first time around in the new fixture.

It takes handling, shipping, storage, inventory, etc. just like a whole new fixture.

What amounts to specialty ballasts are even worse since their is often only a single source for them.

Try and check out the controls and wiring that all three have in common.
A wire that has become disconnected is a lot cheaper to repair than replacing ballasts.

Make sure the ground connection to the unit is also good.

Florescent lights rely on capacitance from the bulb to ground to help strike the arc.

I have found that the ballast housing must be solidly grounded to the fixture. I had some new fixtures in which the paint (or powder coating) insulated the ballast from the fixture housing and they would not work.

I checked voltage to each fixture and they all show 120v, so they're good. If I think about what exactly happened more carefully, I can say that the 3 fixtures did not shut down at exactly the same time. It really took many months before all the lights were out. It was the kind of thing where they work for awhile, and then they don't. Being busy, time flies and I lose track of what the lights are really doing. I guess what I'm thinking is that these ballasts could have been going bad over a longer time than I originally stated. It couldn't be a grounding problem as the lighting was fine for 5 years. Maybe that's the expected life for a small ballast like those??? Anyway, unless there is anything else I can check, I think I'll go try to buy replacement ballasts from the manufacturer.

Thanks for all the replies so far!

From your last post, it does appear the chances of all three ballasts failing are somewhat increased, but you could still check a couple more things.

When you measured 120V at the ballast connections, were the ballasts actually connected? A bad switch for the lights, if there is one, could still show a good reading on the load side without the loads connected.

Since a deli case is not the most hospitable environment for electrical connections, you may wish to double check those as well.

As brickeyee and busdriver pointed out, grounds are very important to the operation of fluorescent lighting. You may wish to loosen and re-tighten mounting hardware for the ballasts and lamp reflectors, as well as the incoming AC chassis ground.

If you find touching and moving the tubes around causes them to light, that is often indicative of possible grounding problems.

Then again, it may just be the ballasts. Also, I must admit, I never knew that deli cases here were being manufactured in China!

yosemitebill:
I disconnected each fixture and checked the voltage coming in. I'm not sure which wires to check otherwise as I'm no expert on ballast. Should I check voltage at each end of the fixture where the lamp pins go in?

Otherwise nothing seems to get the lights to come on. Also, the wires go into the housing of the case, so I don't have access to any wiring contacts other than what goes into each fixture.

So now I'm confused. I was probing around the fixture contacts on the middle light and then put the bulb back in. It lit up! Everything is tight but it does go out again once in awhile. If I tap on it it comes back on. I'm still thinking the ballast is on its last legs. If I disconnect some of the ballast wires is there a way to check the voltage and compare to what it probably should be? I'm looking for a definite way to see if the ballast is good or bad or almost bad.

"If I tap on it it comes back on. I'm still thinking the ballast is on its last legs."

Are you tapping it with bare fingers?

If so, check the ballasts cases (especially if they Are metal) and the ground to the case itself from the incoming power.

Any ground connection needs to have star washers to cut through any surface paint or corrosion and make a gas tight bond for long term reliability.

Yes, with bare fingers, and it's just that one fixture. The others are just dead. The ballast is black and doesn't appear to be metal, but I'm going to have to remove them and see. Everything on the fixture looks to be tight. Is there no way to take a voltage reading or something from the ballast to test if it is any good, kind of like testing an old battery that isn't quite at the voltage it should be?

If the case lighting is on the same circuit as, say, a refrigeration unit, then another reason that all the ballasts might have failed around the same time is power spikes from an induction motor turning on and off. Motors (like freezers and such use) can put power spikes on a circuit that are very rough on electronics (like those in an electronic ballast). A well-made ballast should be prepared to handle such; a cheap one might not.

However, please consider this to be a low-probability situation.