I love the magnetic-ballasted, PL-type CFL's and have them in desk lamps & in adapters in other areas of my house, but there is a nagging problem that I can't figure out. I can understand why lamps may flicker/pulse at end-of-life (rectification) and in cold temperatures, but I have been noticing my lamps (even new ones) flickering after they have been on for a while, at normal room temperature. The entire tube pulses/flickers slightly (not like startup or end-of-life flicker, but an irregular dimming), enough to be annoyingly noticeable. Turning the light off for a few seconds & back on usually cures it, but the problem will reoccur eventually. I also have a 22w circline adapter (also preheat choke ballast) that does this.

My guess is there is some kind of harmonic being set up within the discharge that gets the lamp into this pattern. I thought it might also be the mains voltage dipping but haven't been able to prove this pattern.

Any explanation? Any cure (i.e. adding a capacitor?) It doesn't seem to matter what brand of lamp or ballast is used.

I've noticed something similar in my work, it came out there were loose connections in building's electrical wiring (there was AC water leak damaging the wiring), what causes tiny sparks and these created "rectifiers" manifesting themselves by fluorescent flicker.

Sometimes the flicker is result of interference between tariff control signals (PAM ~5..30V at few 100's Hz, exact frequency is designed so, it has no common harmonics with 50Hz mains; superimposed to the mains voltage), non-PF corrected rectifier loads (e.g. PC,...) and serial choke ballasted lamps. The rectifier is strong nonlinear element, causing the mains harmonic to create very low frequency beat tones with the tariff signals in the current, this current create wiring drop, so in turn such low frequency voltage components, what then cause inductively ballasted lamps to flicker. The only solution to this is to decent power factor corrected power supply units in PC's (the highest power home device with rectifier at it's mains input) or rewire your home, so PC socket use separate wiring from the main "fuse-box".

Thats interesting. Is there any electric interference that could cause MV lamps to flicker(like FL's in cold weather) about 1-2 sec so bad that those will turn off(restrike after cooling). Lamps been used by choke type 230v ballast and wattage is 125W.

Thats interesting. Is there any electric interference that could cause MV lamps to flicker(like FL's in cold weather) about 1-2 sec so bad that those will turn off(restrike after cooling). Lamps been used by choke type 230v ballast and wattage is 125W.

Generally any low frequency (subharmonics or beat tones below 50Hz) or DC component on the mains voltage in combination with worn out lamps (so they are more sensitive to voltage dips).
What might be cause of such components? Any odd load on common and long power line (so it exhibit higher resistance) - once i had an issue with single phase induction motor in wood chip cutter connected to he same phase as the yard light - when filled with some thicker branch, the irregular mechanical load from the blade wheel caused irregular current surges, yielding to odd subharmonics in the mains (the wheel rotate ~15 blades/second, what does not divide well with 50Hz mains, creating huge subharmonic beat tones)

I have the same problem with mercury lamps operating on simple HX ballasts here - sometimes they will flicker/shimmer, often right before they reach full brightness on warmup, and often for a few minutes at a time at full brightness. I've even seen an HPS do this. The one commonality: No capacitor in any of these ballast circuits.

Even with my computers turned off & unplugged, I am still having the PL fluorescent flicker issue. But with all the electrical stuff in my house, who knows the exact cause. I was thinking of trying it plugged into an isolation transformer to see if this makes a difference.

I'm wondering if adding a capacitor for power factor correction to all my simple ballasts would fix the flickering too?

Adding PFC capacitor would not fix anything.
There are simply mains subharmonics present in the network, what cause such flickering.
What to look for:
- Larger/older/worn out chiller machines (air conditioning, chiller, freezer,...): Here the periodic mechanical load of the motor (few Hz below mains frequency) tend to create beat tones with the mains (those few Hz)
- Sparking starting relay of above (if mechanical)
- worn out water pump or similar device (nearly stucked bearing cause irregular mechanical load)
- Other single phase motors with irregular load (e.g. wood chopper caused worn out MV run on serial reactor to extinguish - mainly when the chopper got some harder "bite")
- Bad/sparking contact somewhere in the installation - VERY DANGEROUS FAULT
- high load with rectifier on the input (PC, large TV - mainly plasma,...)


Lead ballasts are not as sensitive, as impedance of the capacitor (dominant ballasting impedance) is very high at low frequency (unlike on inductance, what has very low impedance for them).

And flicker of MV before reaching full brightness is normal - boiling mercury sometimes splash and cool down a bit the electrode, what cause the arc root to "dance" a bit. Once full mercury dose is vaporized the flicker (if caused by this phenomenon) disappear - as there is no liquid mercury to boil anymore...

I've seen this shimmering effect also in a few of lights, some of mine shimmer when warming up like the aforementioned 175W mercury vapour fixture which uses a simple NPF HX ballast.

Two of my fixtures like my 150W HPS fixture which had a HPF HX ballast and my magnetic F32T8 rapid start wraparound which has a HPS ballast shimmer only when my laser printer which is on the same circuit as the other two lights is turned on, so I guess it's introducing some kind of mains subharmonics in the network and causing the lights to shimmer.

I once had a 4-channel disco light controller that I used to control some 300W par56 lights. it worked well but during its operation it used to give some interference to power network. you could easely see it on FLs and HIDs. Also when my laser printer(HP laserjet 4M+) is operating you can see the same effect(rapid but small changes in FL and HID brightness.