Electronic Ballasts for shop lights.

[mnemonic76]

I installed a bunch of electronic ballast shop lights in my garage several years ago. In less than 6 months they started to fail. I think there were 15-20 fixtures initially installed, and now about 4 or 5 still work. I have replaced a few with brand new ballasts, but it has always eaten at me that the failed ones don't have any obvious signs of failed components. Can anyone suggest a troubleshooting strategy for an experienced electronics hack? I have done a lot of soldering and component replacements in various circuits including LCD power supply sections and audio equipment, but I don't posses fundamental electronics training.

I have a DMM and access to an osciliscope from work, and really want to fix these darn things and LEARN something in the process.

If anyone out there is willing, I will send you a ballast to look at 'in person' and I can take all the pictures in the world.

Thanks in advance.

mnemonic76

 

[C1]

If they are the standard oil filled "reactive" type then they arent meant to be repaired.

They are probably failing becase they are junk. A good ballast can cost over $100. You might have better luck buying quality units off eBay: http://compare.ebay.com/like/320952761499?_lwgsi=y&ltyp=AllFixedPriceItemTypes&var=sbar

 

[Mark R]

What type of lights are they?

Fluorescent? Halide/Sodium? While conventional reactive ballasts for these are essentially identical (just a big inductor) in series with the lamp, electronic ballasts are hugely different.

Fluorescent output high-frequency AC (at about 20 kHz), whereas HID operate at low-frequency AC (about 100 Hz). AC at 20 kHz is very easily regulated electronically. HID ballasts require regulation at 20 kHz, before smoothing and rectifying then inverting to 100 Hz AC square waves - never mind the 5 kV series ignitor circuit.

Assuming you mean fluorescent, the electronic ballast is relatively simple:
1. EMI filtering
2. Rectifier
3. Step-up regulator with power-factor control
4. Reservoir capacitor
5. 20 kHz Half-bridge inverter
6. Inductive ballast
7. Semi-resonant tank for ignition.

Quite often, electronic ballasts will use highly-integrated ASICs which incorporate control for both the high-power-factor pre-regulator and the output inverter in a single chip.

There are lots of ways these could fail:
1. Inadequate surge protection. Unlike in an old-style PSU, the input MOSFET is connected directly to the input rectifiers, it is therefore exposed to the full force of mains transients. In a non aPFC PSU, the first switch is protected by the reservoir capacitor which will absorb surges.
2. Poor quality capacitors or overheating. Ballasts must endure a harsh environment, and capacitors of low quality will be rapidly destroyed.
3. Corrosion. Electronic ballasts are not hermetically sealed and are vulnerable to condensation and corrosion. They should not be installed outside, or in unsealed/unheated environments, unless specifically rated for outdoor use.
4. Inadequate voltage rating of the output MOSFETs. These have to be able to generate the 1.5 kV ignition using the resonant tank. Inadequately rated MOSFETs may be damaged by these voltages.

 

[mnemonic76]

I'm sorry guys, I forgot to mention they are fluorescent. Dual T8 tubes I think. Thanks for the responses. I do actually want to attempt to repair these, and not buy new yet. Mostly due to the expense of replacing all those ballasts, but also it just seems so wasteful. If I can replace a lodger, or capacitor or something, it is more economically sound and less trash!

They are definitely not the old oil-filled type. They are fully pc board mounted components. Although the garage is not climate contgrolled, there seems.. no signs of overheating parts, etc to be no signs of corrosion visible. They actually look very clean inside. No bulging/leaking caps.

Can someone outline a basic troubleshooting process for these? After of course making sure the bulbs are ok, the units are cold. I am not sure if I can just follow circuit traces on the board and check for voltage passing through or if the design of the circuits make this impossible.

Thanks for helping me learn.

 

[sm625]

I was in a similar situation. I had 3 bad ballasts. The whole damn bank of lights went bad. But I'm not even going to replace them. I dont see what these lights offer above and beyond the typical 13W CFL's you can buy for a dollar. These CFLs use less power, cost less and produce loads more light per dollar spent.

 

[pm]

Mark's post is awesome - as usual. Beyond what he wrote, I have my thoughts as a frequent repairer of electronics. I have two methods - the methodical method, or the poke around method. For methodical, I learn how the system works, I get out my DMM and oscilloscope and start at the power input and work my way through the system. Alternatively, the method that I usually use for complex electronics (like LCD/Plasma TV's) is to go in and just poke around looking for blown stuff. I check for blown electrolytic capacitors with my DMM by looking at the capacitors and checking that they are all an open-circuit with my DMM. I check resistors match their values. I check cold-solder joint fails on inductors and I look at the transistors and check the resistances of the legs. But more than anything else, I just look for stuff that seems broken.

Another method that works particularly well on consumer electronics is to google the model number along with the problem. I'll often find a page that details the exact issue that I'm seeing - thus saving me the trouble of figuring it out for myself. And then usually there's specific advice from people about how to fix it. I wouldn't think this would work for a ballast though.

Given the relative simplicity of a ballast, I'd probably do the methodical approach - particularly if there wasn't an obvious problem. Anyway, not sure that this helps, but I figured I'd throw it out there.

 

[pwzf4nxz]

I have bought quite a few of these solid state ballasts also. The are all made in China and as far as I can determine, they are for the most part, JUNK. I install a new ballast (by the way, these are in my garage, which is not heated, but nevertheless out of the weather) and within a month, they are failing. I am really fed up with these inferior products. Even in summer months, they fail within a month or two.

 

[stormkroe]

I know this thread is a few weeks old, but I thought I'd give an opinion to it. I've run into this with shops that do alot of welding. Some cheap ballasts don't survive the inductive kick of welders, and I've had good luck simply making sure that the lighting is on a different phase from the welder. Of course, this isn't possible in single-phase services with 240v welders, but most shops that big are 3 phase. If this seems to be your problem, a choke or L filter on the lighting circuit might stop this or slow it down.

 

[mnemonic76]

Well, I did do quite a bit of welding in the garage around the time I installed all the cheapo fixtures. The welder is just a little Lincoln MIG that runs on 120... but I do have a big compressor that runs on 240... interesting. I also read that you can have problems with a bunch of the fixtures powering on at the same time due to cheap design... they are on two circuits I believe, but three switches so they aren't ALL being powered up at exact same moment.

thanks

 

[NeoPTLD]

Replace them ballasts with brand name ones. Don't tamper with line operated devices that will frequently get used unattended.