Light alert!
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Cargo Master
Joined: Jan 2004
Posts: 2,512
Likes: 8
From: Cook Forest and Irwin PA
Light alert!
Anyone have a flourescent tube shop light, the one that uses little 13W tubes, 1 or 2?
I have one, from Sears, you can turn them on both or one at a time.
Mine stopped working. So, I took it apart.
the things use electronic ballast (no surprise there)
what was surprising when mine died after perhaps 1-2 months (xmas gift last year) was that I found they ARE ALWAYS ON.
the switches merely complete the light circuit on the secondary side of the transformer, the primary side is always running.
They use, at least in my case, a push pull arrangement of high speed switching transistors in a to220 case with no heat sink. they oscillate at higher frequency than 60hz to maket he tube 'fast start'. I had one tranny fail to the collector so the mounting tab was carrying +.
Since these are high voltage units, it possessed 240v DC.
I dunno about you, but I leave my shop lights plugged in all over the place, so I dont have to search far and wide. Given that my eyes are 44 years old, I like bright. this is the price I pay I guess.
I soldered in a new fuse and the one lamp still works and I have not found a supply house to source new BUL128A units, and sears, even tho it has a 1 year warranty from sears - wont honor it. when its a gift you have to have the receipt. perhaps I will machine a heat sink for them (tight fit!) but I worry about the proximity of the heat tabs/sink and the tops of the supply caps. DC jolts burn.
I have one, from Sears, you can turn them on both or one at a time.
Mine stopped working. So, I took it apart.
the things use electronic ballast (no surprise there)
what was surprising when mine died after perhaps 1-2 months (xmas gift last year) was that I found they ARE ALWAYS ON.
the switches merely complete the light circuit on the secondary side of the transformer, the primary side is always running.
They use, at least in my case, a push pull arrangement of high speed switching transistors in a to220 case with no heat sink. they oscillate at higher frequency than 60hz to maket he tube 'fast start'. I had one tranny fail to the collector so the mounting tab was carrying +.
Since these are high voltage units, it possessed 240v DC.
I dunno about you, but I leave my shop lights plugged in all over the place, so I dont have to search far and wide. Given that my eyes are 44 years old, I like bright. this is the price I pay I guess.
I soldered in a new fuse and the one lamp still works and I have not found a supply house to source new BUL128A units, and sears, even tho it has a 1 year warranty from sears - wont honor it. when its a gift you have to have the receipt. perhaps I will machine a heat sink for them (tight fit!) but I worry about the proximity of the heat tabs/sink and the tops of the supply caps. DC jolts burn.
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Well I for one, am pretty impressed with your troubleshooting.
I did a little googling, and your part is made by STmicroelectronics -- seems to mostly go through wholesalers. However, the site did offer free samples
STMicroelectronics - Product Family
Don't know if you can meet their requirements, but it doesn't cost anything to try.
I'm not sure if a heat sink will help ( won't hurt). When the lamps are off, I presume that the oscillator is pretty lightly loaded, so that shouldn't be a big deal. And it's a pretty stout transistor, per the datasheet, so the 'on ' time shouldn't be a big deal either. But that's all speculation.
Good luck,
I did a little googling, and your part is made by STmicroelectronics -- seems to mostly go through wholesalers. However, the site did offer free samples
STMicroelectronics - Product Family
Don't know if you can meet their requirements, but it doesn't cost anything to try.
I'm not sure if a heat sink will help ( won't hurt). When the lamps are off, I presume that the oscillator is pretty lightly loaded, so that shouldn't be a big deal. And it's a pretty stout transistor, per the datasheet, so the 'on ' time shouldn't be a big deal either. But that's all speculation.
Good luck,
Junior User
Joined: Nov 2008
Posts: 97
Likes: 0
The switching transistors typically put the frequency above 20KHz...more to make coils smaller than fast start....the cheezy low voltage track heads use the same technology...the transformer outputs 5 amps and is about the size of a 1 amp unit...same sort of deal on aircraft...most are at 400Hz. The Panasonic, Sylvania or Philips lamps seem to last the longest.
