There is a S-like curve between lamp ignition voltage and cathodes temperature (which depends on preheat voltage and time). Lamp starts to glow when OCV is above this curve. Curve shape depends on a lamp type, exact lamp sample, grounded objects around and even glass surface resistance. And of course different ballasts will have different OCVs. Later ignition is beneficial on the lifetime as the lamp spends less time in glow discharge, but the risk of overall ignition fail increases.

We all know that fluorescent lamps sort of fade on while starting up on a rapid-start ballast. Most of the time, the lamps illuminate dimly as soon as they are turned on, and then they get gradually brighter or snap to full brightness. However, I have noticed that on some ballasts, there can be a split-second delay between when you turn the fixture on and when the lamps start glowing dimly. It doesn’t seem to have any adverse effects on the functionality of the fixture, just a weird effect.

One example of a ballast that behaves this way is the Universal 446-LR-TC-P ballast from 1985 that I installed in my bathroom light recently. I have noticed that after it has been switched off for a while, when you go to turn it on again, there is a ~0.5-1 second delay before the lamps begin starting up. If the lamps are already warm when starting up, the delay goes away.

Does anyone know why this delay occurs? I have noticed it on a handful of ballasts over the years, but the vast majority don’t seem to have this effect. Is it something that caused by a specific pairing of lamps and ballast, usage conditions, or just something intrinsic to the ballast?

Sorry if this might come as annoying but what has the better value?

A single GTE era Sylvania 400W deluxe white clear-bander mercury vapor bulb for $29.19 USD.

A lot of four GTE era Sylvania 250W deluxe white mercury vapor lamps; one of the lamps is a Safeline. They all have a standard fully coated top. The cost is $36.30.

Which listing has the best overall value?

I want to covert an old Dana Lighting Aerolite alarm clock-radio with built in folding halogen lamp to a deaf alarm clock. My plan includes sticking a relay across the lamp switch and tapping the alarm signal at the buzzer position on the switch to trigger the relay coil through a MOSFET.
Can you hunt up the datasheet for the MSM5096B alarm clock chip? I've been unable to find it.

Holy crud you're right. Embarrassing. Makes sense now.

Or something (some piece of paper, plastic film,...) stuck in the tube could be fluttering there and create the noise. And once tried again, it got freed and so the noise stopped...

Where did you find it defined as Ellipsoidal-Diffused?  I've always heard that the D stood for Dimple or Dimpled.

I was just looking up what the different ANSI lamp shape codes meant and came up with something weird. First of all I though "BT" was blown tubular, but it is actually bulged tubular. I feel like that rolls off the tongue less readily but whatever, not what I am talking about here. Here is my problem:

"E" stands for Ellipsoidal. "ED" stands for Ellipsoidal-Diffused. So the same as E, but diffused... That alone is weird to me, because we don't specify whether it is or isn't diffused in any other ANSI lamp shape code. There isn't any AD or BTD or PSD any of that crud.

Even more, E25 and ED18 are both similar elongated ellipsoidal shapes (the borderline-tubular shapes that I am not a huge fan of). Neither of these are diffused, despite the name of ED18 suggesting that it would be. That is because these rules are almost never ever followed for some reason. Barely anyone uses E to describe lamps, only ED, even when the lamps aren't diffused.

Why was a diffused version of the "E" code ever created, and why has E fallen out of favor for the incorrect use of ED to describe everything ellipsoidal, no matter it's translucency?

Cooper Lighting/Lumark MP Micro-Pak

I never bring up the context of lighting to the public, due to that in the days that we live we will find someone that will make fun of you for this, and will do it untill your just tired and dead of it (I know what I'm talking about). I just don't talk about it, I keep it private. Only people from my family,  or someone who I strongly trust and know him / them for a long time.

As well, I know that people on this platform that I don't know well will see me talking about lighting, but this is a lighting platform