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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 21st Apr 2021, 12:01 am   #1
Julesomega
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Default PROTEC Fire Detection PCB WEEL021

Looking for something to throw away I was looking through a boxful of PCBs and came across this which looked too interesting to throw away. I had for some reason labelled it as an inverter for fluorescent lights belonging to a 24V system of emergency lighting

Applied 24V DC and it took a sensible current and gave rather more volts out. The input is reassuringly labelled AC+ and AC-, the outputs aren't labelled. Off-load it took 120mA and gave two separate outputs of 60V pk-pk at 10kHz

The one device is marked LM8711 which doesn't show up in the datasheetarchive, but I presume it was one of the Electronic Lamp Ballast Transistors which were offered about then (date code 76)

I can only assume it was made to run two 8W fluorescent tubes without bothering to heat the filaments, but has anyone come across Protec or similar inverters?
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Old 21st Apr 2021, 12:15 am   #2
McMurdo
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Default Re: PROTEC Fire Detection PCB WEEL021

A quiick google shows that Protec still make emergency fluorescent light units. Maybe from one of those?

Most caravans of course have (or used to, before LED!) little inverter boards for their 12V 8W fittings. They didnt have preheat either.
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Old 21st Apr 2021, 12:38 am   #3
Terry_VK5TM
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Default Re: PROTEC Fire Detection PCB WEEL021

And that transistor doesn't appear to be an LM 8711 - looks more like SM 8711 and I suspect it is a house number.
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