Old Fluorescent light (two T12)

[Excavatoree]

I purchased 10 (EDIT 13)  Fluorescent luminaires for my basement a long time ago.  They have been discontinued, and to be honest, were pure crap when I bought them.   These have purely magnetic ballasts, no electronics at all, other than a capacitor and what I assume is a bleeder resistor.  One bulb won't start - it flickers for about 10-15 minutes or longer.  It was finally starting, but it keeps getting worse.  I suspected the capacitor, from the way it looks.  It's the most awful capacitor I've seen.  It looks like it has no cover.  There's no labeling at all.  It measured about 2.5 microfarad.

I don't have many capacitors rated in the neighborhood of 220 volts (110V, US system, plus safety margin) but I did have a 2.2 microfarad 400v capacitor.   (A film capacitor in a plastic box) I used test leads to add it in parallel.  Adding this caused the light to work properly, so I guessed it should be about 5 microfarad, and I wanted at least a 250v rating.

I got lucky and found an old internet post from someone with the same luminaire. His capacitor was marked.  I was correct in my guesses, it was a 5 microfarad, 250V AC capacitor.  Digikey was out, but Mouser has one that I think is acceptable.  (had to find one that would fit in the small space below the ballast)

However, I have no experience with this sort of capacitor selection.  Does this part seem like something that would work?  If anyone knows of anything I'm missing, any input would be appreciated.

https://www.mouser.com/ProductDetail/KEMET/C4GAFUC4500AA1J?qs=pqRVuuzkf6beJcsy69%2FR8Q%3D%3D

[CatalinaWOW]

I am not familiar enough with electrical code requirements to know if this has all of the proper regulatory boxes checked, but would feel comfortable using it myself.  I didn't see anything in the data sheet that worried me and the stated applications seemed almost appropriate.

[108CAM]

The knowledge I've gained from being in a forum with lighting enthusiasts will me pinpoint your issue.

Firstly, the capacitor is only there for correcting the Power Factor, primarily in larger installations where the current drawn by the lights starts to affect the mains installation they're connected to.

In your case, the flickering tube tells me that the tube is going bad and needs to be replaced. You can confirm if the tubes are the issue by taking the tubes from a working light and installing them in the faulty one. If it starts normally, you'll only need to replace the tubes.  Just pop into your local hardware store and head to the Lighting/Electrical department, locate the fluorescent tube shelf and find a matching replacement.

If the problem persists, it's likely the ballast which is failing. It can be replaced but can be rather fiddly with all the wires.
Some photos of the fixture in question would be helpful for further pinpointing the issue.

[james_s]

If the fixtures were good quality or interesting vintage then I'd advocate repairing them but since you said they were pure crap when you bought them why don't you just replace them with modern LED fixtures? Alternately you can get LED retrofit tubes that you bypass the ballast and wire them directly to power.

[Ian.M]

See https://www.repairfaq.org/sam/flamp.htm

If your magnetic ballast has glow starters, a bad starter can also cause the lamps to cyclically flicker rather than start.  However worn out tubes are far more common so always try new or known good tubes first. 

If you've got glow starters, compatible electronic starters are a worthwhile upgrade, which can extend the life of the tubes and reduces flickering on startup.

N.B. glow starters *MUST* be matched to the tube size and length they are used with, as they must not restrike  with a normal tube's running voltage across them - usually the starter will be marked with the tube size and wattage range its good for, the wattage being proportional to the length. 

N.B.2.  Magnetic ballast fluorescents in good condition emit far far less EMI than any electronic ballast lamp. If you have *any* interest in metrology or low level signals you'll probably be rather unhappy with the increased background EMI levels if you replace them with modern alternatives.

[james_s]

Preheat start fluorescents are rare here except in sizes 18" and under, I have a couple of electronic starters I got from the UK years ago but I've never seen one sold in this part of the world.

[jonpaul]

hello worked in ballast and lighting design since 1970s.

The ancient fluorescent magnetic ballasts have a limited life, poor efficiency and run mercury contain bulbs.

Rather than repair this decades old light, suggest to remove all the old fixtures and use modern LED area lights or fluorescent style LED.

Costco, Amazon, Home Depot have a wide variety


As the energy cost of the lighting will be much lower 0, the cost to replace the old fixtures is recouped in a few years.

Finally the capacitors are for power factor or part of the ballast circuit.Special low cost paper / oli caps that are self healing resist transients.

Not easy to find a correct replacement cap.

Bon courage

Jon

[Vincent]

Is this ballast preheat (with starters) or rapid start (without starters)?

Many of those so-called "rapid start" ballasts that were at one point used everywhere in US and Canada used capacitors, but not only for power factor correction. The capacitor is often part of the actual ballast and does part of the current limitation. If it's a film capacitor that loses capacitance over time, the resulting increase in capacitive reactance leads to lower lamp current and eventually starting issues.

[jonpaul]

Most fluorescent 4' fixtures are rapid start, no preheat.

the most likely fluorescent fixtures failures

1/ bulbs
2/ bad lamp socket contacts
3/ bad preheat starters if present
4/ failing ballast magnetics windings
5/ PFC or lead lamp capacitor

j

[Vincent]

In commercial and industrial applications that's been true for quite some time indeed. But you would be surprised how many of the older preheat fixtures are still around in homes and garages.

[SeanB]

No, that capacitor is not there for PFC, but is a resonant capacitor for the 110V resonant ballast, or it is one of the parts needed for a lead lag ballast connection, which was very common on old fixtures, which need to use an autotransformer to step up the voltage to the tubes, as a T12 4 foot lamp will not otherwise start reliably on 110VAC, if at all. The ballast will have 2 yellow leads that connect to one side of both tubes, and then a set of red and blue leads, which go to the other side of each tube respectively.  Capacitor will be there internally to provide a phase shift, and that one listed will work, though normally you use one meant for motor run applications, which typically has a 275/400VAC rating.

However you can install LED retrofit lamps easily, with only needing to remove the ballast, cutting the wires off at the ballast body ( power off to the fixtures first) and using only the yellow wires to provide power to the one end of the tube. Thus you connect the one yellow wire to the black line wire, and the other yellow wire to the white neutral wire, and leave the red and blue pairs just with the ends taped up, and remove the heavy metal potted ballast entirely. Then put a mark on the end the yellow is, and install the new LED tubes so the ballast end (typically the end with the printing of the type on that side, or marked with power this end) in there, and turn on the power. Old ballast units put into the pile of scrap metal, and send to the recycling yard, as they contain a lot of copper wire, though getting it out is messy, as the potting will be either bitumen or polyester resin with a sand fill.

[Excavatoree]

Thanks, everyone for the input.

I will say that I do intend to replace these with LEDs, but this is just my basement.  If it were a home business space, I'd have spent the money for LEDs a long time ago.  As it's just for me dicking around, the LEDs are still a bit too expensive to replace all 13 fixtures.  There are inexpensive LED fixtures, but I like 4100K color temp, and the ones with the same light output as the T12s are all 5000K or even 600K.  I figure it won't be long before they are cheap enough - that's why I'm keeping this junk working as long as I can.  Plus, I just like fixing something instead of throwing it out.

Keep in mind these aren't on long enough to get a significant return on investment from lower electricity cost.  I could just replace one, and I'll accept all criticism for not doing so, but right now they all match and I don't like having a rag tag set of luminaires.  That's not a good technical reason, I'll admit, but the repair is inexpensive.  The oldest are A decade old, but not decades.  (15 years or so since I installed them into the dark basement with only 2 100w bulbs) 

Many have been replaced with a revised version.  These are electronic ballasts and are easier to fix.   I've replaced electrolytic capacitors in all of them, and one had a few other bad components.  (Triac or transistor, some resistors)  My mistake was not buying more of these when they were available.  Until now, I threw away the old magnetic ballast lights, not realizing the cap was bad, and not realizing I could find the value. 

As the discussion has revealed, these are rapid start.  The failed lamp doesn't start reliably, but did when the capacitance was 5 microfarad, as designed.  (well, as reported by the anonymous forum member and "verified" by my experience.)

[David Hess]

The common cheap ballasts use a series resonant circuit instead of magnetic ballast, and have a film capacitor of about that size.  The included film capacitor is so cheap, that I would not hesitate to use any 250VAC or 400+ DC volt film capacitor from Mouser or similar as a replacement.

On many of those fixtures, I replaced the series resonate ballast with a modern electronic ballast for either T12 or T8 bulbs, which is especially nice in the garage in winter although it still takes a few minutes for the bulbs to warm up to full brightness, but at least they start.

[james_s]

In commercial and industrial applications that's been true for quite some time indeed. But you would be surprised how many of the older preheat fixtures are still around in homes and garages.

But he said he bought these 12 years ago, that's well after preheat went away. I've always liked preheat start fixtures, most seem to run the tubes harder, they're significantly brighter than rapid start with the same lamps. I wish I'd kept the old industrial fixtures I had years ago.

[Excavatoree]

Sorry to bring this thing back up, but the repair seems to be working.

Someone mentioned the retrofit tubes.  My impression is that the "direct wire" type are better than the ones that replace the fluorescent tube without re-wiring.  Is that correct?

Thanks, again, everyone.

[james_s]

I have retrofit tubes in my kitchen that are working fine from the existing F32T8 electronic ballast, I'm not sure whether they work with those weird cheap resonant ballasts though. I think I would just leave them alone until they fail and then upgrade. I've had people give me good quality fluorescent fixtures several times so you might find some from somebody that's upgrading or a building being torn down.

[DavidKo]

I have bad experience with electronic ballasts, after few years they were dead (after the guarantee). Instead of buying the good ballast (but which one is good), it was cheaper to buy whole device with starter and magnetic ballast. Worked till replacement with LED lamp without any service (only tube replacements).

[David Hess]

I have bad experience with electronic ballasts, after few years they were dead (after the guarantee). Instead of buying the good ballast (but which one is good), it was cheaper to buy whole device with starter and magnetic ballast. Worked till replacement with LED lamp without any service (only tube replacements).

The ones I bought were name brand from GE or Philips or someone and none of them have failed yet.  At the time they were like $25 each from Home Depot.

[james_s]

Mine are Advance which Home Depot used to carry, seems like I did have one fail at some point but the rest have been fine. I've even used them to run low pressure sodium lamps, they work perfectly for that by paralleling both outputs from a 2 lamp ballast for the 18-55W lamps and 3 outputs from a 4 lamp ballast for the 90W lamps.

[CatalinaWOW]

The only problem I have had with LED replacement tubes are fitment problems.  Apparently whoever designs and markets these things didn't look for standards on dimensions and just measured a couple of fixtures.  Or maybe dimensional QC is terrible.  I have had to slightly bow the LED tubes to get them to fit between the sockets.  A little worrisome, but so far no issues.

[wizard69]

Exactly what I'd suggest.

If the fixtures were good quality or interesting vintage then I'd advocate repairing them but since you said they were pure crap when you bought them why don't you just replace them with modern LED fixtures? Alternately you can get LED retrofit tubes that you bypass the ballast and wire them directly to power.