fluorescent bulbs flickering - why is this so hard?


So, in my laundry I have two, two bulb units, installed at the same time.
Over the past 10 years, I've swapped out various bulbs. But one fixture simply will not illuminate the bulbs (flicker, partial ignition). These are relatively new electonic ballasts, no starters and are at room temperature.
Change the bulbs: nope, still flickers. Take the old bulbs, put them in the unit that works fine. Both bulbs work fine.
Check the line voltage for the misbehaving fixture: solid at 123V. Verified grounds, cleaned, made sure no paint.
Okay, what the heck - new bulbs. Still flickering.
Must be the ballast - replace it. STILL FLICKERS.
Okay, at this point I'm left with the conclusion that it has to be one of the bulb sockets. Right? Clean them with contact cleaner - still flickers.
So, one has to be bad, or is there something else? How often do sockets fail?
Whipped by a fixture :)
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Try pulling / pushing the wires going into each bulb socket. These can be loose.
"Charlie" wrote in message

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Charlie wrote:

Did you check the type of bulbs specified by the ballast label to be sure you are using compatible bulbs?
For example, there are a few different 4-footers that have 2 pins on each end:
1: 25 watt cheap shop light ones 1.5 inches in diameter. These lamps should only be operated on ballasts rated for these lamps. Ballasts that rated for these lamps may be rated for no other 4-footers, and/or may be OK with 32 watt 1 inch diameter 4-footers, and/or may safely operate (at reduced power) "true 40 watt" F40 4-footers.
Use of 34 watt "energy saving F40" in a 25 watt fixture has significant chance of cranky operation, including flickering and/or snaking/swirling and/or beading/banding, especially in cooler temperatures.
Use of "true 40 watt" F40 / F40T12 is not as bad as use of the 34 watt one, but it may get cranky as above, especially in cooler temperatures.
2: 1 inch diameter F32T8 32 watt modern "newfangled" 4-footers. They should only be used with ballasts rated for them (in fixtures having ballasts rated for them). Ballasts rated for these are usually not rated to run any other 4-footers, although a few may be rated to run 25 watt T12 (1.5 inch diameter) 4-footers. Most ballasts for these will usually run European 36 watt 1 inch diameter 4-footers OK or reasonably OK, but this is not guaranteed. Most ballasts rated for 32 watt 4-footers and shorter length lower wattage T8 (1 inch diameter) lamps/bulbs will run the 25 watt T12 4-footer at least fairly OK and will often run "true 40 watt" F40 "fairly OK", at least in warmer temperatures. (WARNING - if the ballast is not actually rated to operate these, then officially you are abusing the ballast by using it with such lamps/bulbs.) Use of F32T8 ballasts with 34 watt T12 will underpower those to extent of fair chance of "cranky" operation, including beading/banding, flickering, and/or snaking/swirling, especially in cooler temperatures.
3: European 36 watt 1 inch diameter. Ballasts for those usually take 230 volts and are often compatible with 240 volts. Ballasts for these tend to do at least fairly well with North American 32 watt T8 (1 inch diameter) 4-foot lamps/bulbs and have fair chance of doing fairly weill with 4 foot 25 watt T12 (1.5 inch diameter), and with "true 40 watt" F40T12 although underpowering those somewhat. Ballasts for European 36 watt 1-inch-diameter 4-footers have slightly better prospect with 34 watt 1.5 inch diameter bulbs than North American ballasts for the 32 watt ones - but that is not saying a much good news in that area of running 34 watt T12.
4: 34 watt "energy saver" version of F40T12:
Those have some tendency to be cranky, especially in cooler temperatures. These also need to be used in fixtures (or run by ballasts) specifically rated for these 34 watt lamps/bulbs.
These bulbs tend to work OK in fixtures (or run by ballasts) rated for "true 40 watt" F40 / F40T12. If the ballast is rated for 40 and not 34 watt, then the ballast's life may be shortened by using it with the 34 watt "energy saver F40 / F40T12".
Ballasts that are rated for both 40 watt 4-foot F40 and 30 watt 3-foot F30T12 (1.5 inch diameter), especially if of "rapid start type", tend to be OK with 34 watt 4-foot bulbs/lamps.
One common ballast failure of dual-F40 rapid start ballasts that is more common with 34 watt bulbs has main symptom that the ballast "eats bulbs", 2nd-place-most-noted symptom is line current being something like 1.5-1.7 amps rather than around .8 amp. 3rd place is the bulbs running only slightly abnormally bright and/or flickery and/or off-color and/or at slightly higher temperature than normal.
5: A much less common one - the 35 watt "energy saver F40 / F40T12". This one is significantly less "cranky" than the 34 watt version is, due to having gas composition more like that of "true F40" than is used in the 34 watt version. It usually works A-OK with any ballast and in any fixture rated for the "true 40 watt version". As for being-hard-on-the-ballast - the 35 watt version of F40T12 bulb is OK to use with ballasts rated for use with both 40 and 34 watt versions, and is OK with ballasts rated for both 40 watt 4-foot and 30 watt 3-foot 1.5 inch diameter versions, as long as starting method compatibility is maintained.
============================================ Other than bulb/ballast compatibility issues, I would worry about non-ideal temperature, beaten-up starters if you are using starters, and any use of those 34 watt "energy saving F40 / F40T12" bulbs that get cranky easily.
Another common problem area - "trigger start", which is a variant of "rapid start" having increased compatibility with "preheat bulbs". My experience is increased crankiness, especially with the dual-20-watt 2-footer ...
(My experience suggests that 20 watt F20T12 2-foot F20T12 tends to be fed more like 17 rather than 20 watts anyway...)
If you have a dual-20-watt / dual-F20T12 fixture taking 2-foot 1.5 inch diameter bulbs, I would replace the ballast (or entire fixture) to use the 17 watt F17T8 (1 inch diameter 2-footer) instead.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Sat, 30 Jan 2010 19:56:29 -0800 (PST), Charlie

Are you sure you have a good solid ground?
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snipped-for-privacy@hotmail.com wrote:

Second that. A good ground is often essential for a florescent light. In order to fluoresce, an invisible field of electromagnetic galactic flux must envelop the apparatus and this band of radiation (derived from the X-Com Interceptor) is essential. It surrounds and penetrates and and binds the fixture together. The force is not strong with this one.
My description may be a tad off, but a solid ground is often necessary.
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snipped-for-privacy@hotmail.com wrote:

If all bulbs partially light at least somewhat over their entire lengths, as opposed to glowing only at their ends or not at all, then the problem is not grounding.
Most likely, you have the wrong type ballast for the bulbs or the wrong type bulbs for the ballast.
Possibly, you have a bad socket ("lampholder" or "tombstone"), or a bad connection in or near one of those.
The fixture may be wried incorrectly - especially if the questioned electronic ballast replaced a non-electronic one.
If you can rule these out, make sure the ballast is receiving proper voltage. (But I remember somewhat 123V from earlier in this thread?) (Make sure the ballast is a 120V one.)
- Don Klipstein ( snipped-for-privacy@misty.com)
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(Make sure the ballast is a 120V one.)
- Don Klipstein ( snipped-for-privacy@misty.com)
Many of the electronic ballasts are both 120/240 and will self-adjust their output (thanks for reminding me).
bob
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Since you have two identical fixtures...have you checked the wiring (compared color for color) just in case there is a difference. I recently had 4-tube, 4-foot, electronic ballast where 3 tubes were out and one dim. Turned-out...the only bad one was the dim one! It wasn't dark at the ends but it was loading-down the voltage. (These were all new tubes when the ballast was changed-about 2 months ago).
bob
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