Author Topic: Do 28w Preheat Ballasts Exist?  (Read 139 times)
108CAM
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Do 28w Preheat Ballasts Exist? « on: March 08, 2023, 10:19:56 PM » Author: 108CAM
Asking this because I recently got an F28T5 cabinet light with an electronic ballast and would like to make a preheat fixture for the 28w tube.
I've never seen a preheat ballast for 28w T5 tubes and don't even know if they exist.
I probably could use an F30T8 ballast which will overdrive the tube by about 2 watts but would prefer an actual 28w ballast.
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Re: Do 28w Preheat Ballasts Exist? « Reply #1 on: March 11, 2023, 04:40:18 AM » Author: RRK
Do you mean linear T5 HE 28W? Officially, no way, datasheet explicitly specifies HF ballast at >20kHz. Also, this lamp runs with low current like old school F8T5 etc tubes at 170mA, but at unusually high voltage around 166V. So it probably will not  stabilize when run from 230V line. If I'd absolutely want to run this at 50Hz, I would hack an autotransformer to about 300VAC and use some mix of ballast chokes with a suitable impedance. Standard starters won't work with such high tube voltage, but two starters in series or a hacked electronic starter may. Electrodes on this tube may be not optimized for preheat current. Also the lifetime will be definitely hit.
« Last Edit: March 11, 2023, 04:58:58 AM by RRK » Logged
Medved
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Re: Do 28w Preheat Ballasts Exist? « Reply #2 on: March 11, 2023, 01:28:37 PM » Author: Medved

I probably could use an F30T8 ballast which will overdrive the tube by about 2 watts but would prefer an actual 28w ballast.


No, it won't be 2 W, but it could be well above that.

Plus the electrodes in these modern T5 (HE and HO) lamps do not handle the low frequency well. When their design was developed while optimizing the design of these lamps, the 50Hz ballast compatibility was just "thrown under the bus" in order to get the extra efficacy...
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Re: Do 28w Preheat Ballasts Exist? « Reply #3 on: March 11, 2023, 04:57:17 PM » Author: 108CAM
So I'd be better off using something like this Osram Quicktronic multi wattage ballast which is designed for fluorescent tubes and CFL lamps between 26w and 42w.
https://media.discordapp.net/attachments/770526034201411586/1084231557360910339/IMG_4081.jpg?width=781&height=586
The specs don't specifically say that it's compatible with F28T5 tubes but am assuming it will work
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Re: Do 28w Preheat Ballasts Exist? « Reply #4 on: March 12, 2023, 03:52:38 AM » Author: RRK
Will grossly overdrive your tube, as these lamps are high-current CFL running at 320 mA!
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xmaslightguy
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Re: Do 28w Preheat Ballasts Exist? « Reply #5 on: March 13, 2023, 12:43:57 AM » Author: xmaslightguy
I once managed to run a F54T5 HO lamp on a F40T12 RS ballast. (had a bit of trouble starting & was a kinda flickery til it warmed up, but ran fine after that)

Lamp current is the same for a T5 HO and a F40T12, but the F54 really needs a higher voltage to start & run reliably (A F39T5 woulda been a better/closer match for that ballast .. but it was only a test not something I intended to put in use)
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