Okay, so there's this Slimline luminaire at the pool I go to. The pool's been open since what seems like the early 70s, and there's a dual F96T12 Slimline fixture hanging in the storage shed. It's only had one lamp in it for as long as I've been going there (since around age 5). So, today I brought with me two 75w Sylvania Daylight Deluxes. After installing both new tubes, I flipped the breaker (acting as a light switch-- likely...), and nothing happened. No buzzing, no flickering, nothing.

I have a few ideas as to what it could be:

• No input from circuit breaker / switch
• Could be a switch that I can't see, somewhere along a wall. Though there is only one cable going from the fixture, and it leads to circuit breaker box (which has a piece of tape labeled 'Lights' on it), so I'm thinking that's not it.
• Could be a bad breaker, maybe? i.e., check if there is voltage coming out of the breaker box / into the fixture at all?
• Maybe one of the leads is not connected internally, ie a socket lead worked its way loose or two connected cables that are corroded?
• Maybe the ballast is failed? Though I doubt it because there is no hum, no spark, it just appears to be dead.

Okay, so now that I've listed some of the possible failure points, what should I try and troubleshoot first? What's a common failure point on these (older) Slimline fittings? Also, for context, it doesn't seem like this fixture ever had a crazy amount of use. I think it maybe went through one set of lamps before someone gave up on relamping it (someone probably only had one replacement lamp, as this one appears to be new).

Also, finally- how do I go about taking off the ballast channel covers? Do they unclip, or are there screws? Thanks you guys.

My first step would be to verify that power is going to the fixture. If it is a plug-in type, just unplug it and see if the outlet has power. Use a receptacle tester, indicator lamp, or just use a phone charger and see if it charges your phone. If not, then there is something in the way, maybe another switch, possibly even a wiring error. I would start with looking for a switch.

If there is voltage present, I would inspect the fixture. Damaged power cord? Maybe the fixture also has a switch, like one of those pull-chains. If not, then it is definitely an internal error, something inside the light. Now that can't be a whole lot of things, it could either be the ballast, or the wiring. I would check the wiring first because it is easy, make sure all the wires are connected and not hanging loose, and give the wires a tug to see if they just fall out or if they are in there good. If everything looks good wiring-wise, and the fixture definitely gets power, then it is almost certainly the ballast.

I doubt it is a bad breaker, those things rarely go bad, but yes it is still technically possible.

As to the physical construction of that particular light, I have no idea because I have never even touched one lol, but I hope this helps!

Thanks @Multisubject . The fixture is hardwired.

So I guess what I should start with is to look for a switch... there's only one place where there could be one, really, and that's behind one of the two refrigerators in the back area, no other area has a wall that's covered or blocked by anything.

I hope I just have to flip a switch... but if that doesn't work (and there's voltage going to the light, and everything is wired correctly) I might as well pull out one of my 60s Slimline strips and install it there... 

Yeah like Multisubject says check line voltage and confirm it's there and make sure all the wiring has secure connections. If there's voltage to the ballast but no life from new lamps and you checked the wiring is good, definitely the ballast.

As for the light, what kind of light is it? If if's a strip light (or a certain shop light style which is a strip light but with a pair reflectors instead on flat covers) made after the 1970s, it should have two approximately 4 foot channel covers that are held in place by two slots at the end of each lampholder bracket and two turn clips. Turn the clips 45 degrees, and slide the covers out from the slot, as you know I'm sure. Older ones can be held with wingnuts, some eight (with two four foot channel covers) or six (one eight foot single channel cover, which may be a tough bear to get in and out. If it's anything else I don't have experience with them.

The most common point of failure when it comes to slimline lights is the ballast if left too long with EOL lamps. I've replaced two recently that only dimly lit up one lamp with a pair of good lamps in each light once and couldn't light a single one at all after that.

@fluorescent lover 40 - it's a striplight with two 4ft channel covers. It doesn't appear to have any wingnuts or such, so I assume it was made in the 70s. (Definitely not 80s as this fixture trumps the ones in my basement by a massive margin in terms of build quality).

I don't think I've seen one without the turn clips or wingnuts before. The covers could also be friction fit, and just pop on and off the light with some persuasion and no tools needed to remove them. I know it's common on some of the older 4ft and under strips but I don't think I've seen those covers on anything longer. Or they could be held by screws (which I don't think so as you probably mentioned them by now if they were).

On most 120V 2-lamp slimline ballasts, each lamp is connected directly to either the hot or neutral line from the wall on the stationary end, and to the ballast’s output on the plunger socket (277V ballasts are the same, except it’s only the neutral that is fed through a socket). In order to ensure the user’s safety from the high OCV generated by an instant-start ballast, the stationary sockets are designed in such a way that power is only connected to the ballast if both lamps are fully seated in the fixture. If somebody maintaining the fixture were to remove a lamp while the fixture was still on, power would immediately disconnect from the ballast because the lamp pin must be inserted into the stationary socket to complete the circuit. The way this safety feature is implemented into the stationary sockets is remarkably simple. There are two contacts inside that connect to the lamp pin, one that connects to the incoming supply and one that connects to the ballast’s input lead. Each socket is designed the same, one is on the neutral and one is on the hot. The problem you’re describing sounds like one or both of these sockets isn’t making a good electrical connection, either to the lamp pin or to one of wires connected to it. So I would take apart the fixture and examine and/or replace the stationary sockets.

Most 8ft fixtures I've seen use either screws, wingnuts, or quarter turn fasteners to fasten the channel cover on. The ones with a split cover are a bit easier to handle compared to the ones with a full length cover.

As for what's wrong with the fixture, I think most of the possibilities has been covered, I suspect there's either no power going to the ballast or the ballast is bad though as most 8ft fixtures tend to buzz when powered on.

If there's power going to the light, the most likely would probably be a problematic disconnect socket or a bad ballast IMO. 

Here's a picture of the endcap(s) and channel cover ending.

Here's another picture...

So, turns out the electrician decided to be extra intelligent and simply cut the live hot and neutral wires and the fixture wires and simply tossed them into the rafters.

Tomorrow, I will bring with me my wire strippers as well as a metal junction box to formally wire it all up. If I can't locate a junction box by tonight, I'll just bring some wire nuts and wire it up that way until I find or buy a junction box.

The bottom two images show the wires cut. In the bottom left image, the right wire was live (off of the breaker) and the left wire was dead (coming from the light). I just find it so incredibly stupid that someone would cut the live wires like that instead of simply disconnecting them at the breaker.

Also, if I were to wire in a switch into this circuit, how would I go about doing so?

I was just about to say this looks like an American Fluorescent style snap-on channel cover, but I see you figured out how to open it.  I'd hope a professional electrician wouldn't leave the wiring in that state.  They should have capped off live wires within a junction box.  The fact that the NM jackets have been stripped back suggests those cables may have been inside a box at one point.  If they were just going to cut them, I'm not sure why they'd go to the trouble of peeling back the sheath.

An easy solution for a switch would be pull-chain on the fixture with a string.  I believe this is a switch knock-out right here, so you wouldn't even need to drill a hole for one.  Wherever you buy the junction box will likely have switches as well.  Not to pry, but do you have permission from the facility to do this work?  Obviously be careful if you proceed.  It sounds like you have access to the breaker, which is good.

@Patrick - yes, I do indeed have permission from the facility. It's a small community pool, and I've known the property manager since age ~4 or so since I've been on the swim team all my life. She even helped me with troubleshooting today by switching the breaker on once I had the multimeter leads on the hot and neutral wires.

Thank you for that suggestion. I might as well install a pull chain- I think it would be the easiest option. How do they typically get wired up?

Looks like the issue turned out to be a pretty simple one! That is kind of terrifying that they just left the wires chilling though. They must have needed that box for something…

Based on the ballast, I would assume this is a late-80s or early-90s fixture. Though I guess it could be a replacement ballast.

To wire the pull chain, simply connect one of its leads to the incoming hot wire and then connect the other lead to the hot wire going into one of the lampholders and eventually into the ballast.

Ace Hardware seems to be a pretty good place to find switches, plugs, and other small electrical hardware. Sometimes, Lowe’s and Home Depot won’t even have that stuff! When you are shopping for a pull-chain switch, double-check that the switch you choose is a regular on-off switch and not a ceiling fan switch. They can look pretty similar and it’s easy to buy the wrong one by accident. Better to triple-check then to have to run back to the store last-minute! 

That's awesome that they're letting you help out.  You could possibly put in a wall switch, but it's tough to assist with that without seeing the layout of the shed.  Although you could put a switch somewhere along the path from the breaker to the fixture, you wouldn't need to do it that way.  A common solution is to create a switch loop.  Here you could feed another romex cable into the fixture (or the junction box), bringing it down to where you want the switch.  Here's a diagram.  That being said, the pull chain is the simpler option.