Any ID on this inductor please? - UK Vintage Radio Repair and Restoration Discussion Forum

Jon_G4MDC · 23rd Jan 2021, 6:36 pm

Here is a part recently removed from a CFL fitting of about 20 yrs ago.

It is the type where the tube had a base consisting of 4 four pins arranged around a square spigot. The tubes themselves were two side by side and U shaped, maybe 6" long. There were lots of these CFLs around but I forget which brand was on them, GE possibly among others?

Inside the lampholder was a PCB, it has bridge rectifier feeding some 22uF 200V capacitors in series and some Sw_mode trickery following. Good to harvest for parts.

I am interested in the input filter inductor. It looks like this. Two pretty identical windings wound on an ungapped(probably) ferrite core .

Any ideas what the ballpark inductance of this might be please?
My facilites for measurement of inductance are lacking.

G6Tanuki · 23rd Jan 2021, 7:04 pm

I guess it's a common-mode RFI-suppression choke, with the 2 windings intended to sit in the L and L supply-lines.

Terry_VK5TM · 23rd Jan 2021, 10:51 pm

Not knowing the design details, it is going to be hard to say without being able to measure it.

To give you an idea of the possible range, I looked up Coilcrafts common mode filters and the inductance values vary between 130uH and 45 mH.

That is only indicative, other manufacturers could be very different.

Jon_G4MDC · 24th Jan 2021, 10:05 am

Thanks both, yes that's what it is. I'm going to try and guess the inductance by adding a capacitor and looking for resonance.

Julesomega · 24th Jan 2021, 11:41 am

3.9mH

Julesomega · 24th Jan 2021, 11:48 am

Another example, 3.5mH
These are from smaller CFLs than yours, I think

Julesomega · 24th Jan 2021, 12:37 pm

Larger CFLs may have much lower inductance chokes: this one is from a CFL with three U-shaped tubes, rated at 20W. The inductance measures only 0.15mH, though that makes me suspicious that it has shorted turns

Julesomega · 24th Jan 2021, 1:58 pm

I must correct my last post: the inductor is tapped. The former broke up as I removed it so I don't know how the two turns were connected, but it may have had a lot more inductance with the turns in series

Oh, btw, I do love this android app Magnifier Plus, it's better than a loupe for seeing small details, plus you can save the images

Julesomega · 24th Jan 2021, 2:12 pm

More on this inductor: the core has a much greater air (glue) gap than the others, about 0.2mm compared with a layer of thin superglue on the others. From this I conclude that it was for a smps operating at high frequency, and nothing to do with RFI suppression

Al (astral highway) · 29th Jan 2021, 7:05 pm

Quote:

Originally Posted by Julesomega

Oh, btw, I do love this android app Magnifier Plus, it's better than a loupe for seeing small details, plus you can save the images

That's really handy, Jules! Looking forward to using that!

Jon_G4MDC · 30th Jan 2021, 10:05 am

Agreed, that magnifier is really useful.

No more done with the inductor but thanks for all the inputs.

23rd Jan 2021, 6:36 pm	#1
Jon_G4MDC Octode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 1,143	Any ID on this inductor please? Here is a part recently removed from a CFL fitting of about 20 yrs ago. It is the type where the tube had a base consisting of 4 four pins arranged around a square spigot. The tubes themselves were two side by side and U shaped, maybe 6" long. There were lots of these CFLs around but I forget which brand was on them, GE possibly among others? Inside the lampholder was a PCB, it has bridge rectifier feeding some 22uF 200V capacitors in series and some Sw_mode trickery following. Good to harvest for parts. I am interested in the input filter inductor. It looks like this. Two pretty identical windings wound on an ungapped(probably) ferrite core . Any ideas what the ballpark inductance of this might be please? My facilites for measurement of inductance are lacking. Attached Thumbnails

23rd Jan 2021, 7:04 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 9,648	Re: Any ID on this inductor please? I guess it's a common-mode RFI-suppression choke, with the 2 windings intended to sit in the L and L supply-lines.

23rd Jan 2021, 10:51 pm	#3
Terry_VK5TM Octode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 1,531	Re: Any ID on this inductor please? Not knowing the design details, it is going to be hard to say without being able to measure it. To give you an idea of the possible range, I looked up Coilcrafts common mode filters and the inductance values vary between 130uH and 45 mH. That is only indicative, other manufacturers could be very different. __________________ Terry VK5TM https://www.vk5tm.com/

24th Jan 2021, 10:05 am	#4
Jon_G4MDC Octode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 1,143	Re: Any ID on this inductor please? Thanks both, yes that's what it is. I'm going to try and guess the inductance by adding a capacitor and looking for resonance.

24th Jan 2021, 11:41 am	#5
Julesomega Octode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 1,085	Re: Any ID on this inductor please? 3.9mH Attached Thumbnails __________________ - Julian It's good here

24th Jan 2021, 11:48 am	#6
Julesomega Octode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 1,085	Re: Any ID on this inductor please? Another example, 3.5mH These are from smaller CFLs than yours, I think Attached Thumbnails __________________ - Julian It's good here

24th Jan 2021, 12:37 pm	#7
Julesomega Octode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 1,085	Re: Any ID on this inductor please? Larger CFLs may have much lower inductance chokes: this one is from a CFL with three U-shaped tubes, rated at 20W. The inductance measures only 0.15mH, though that makes me suspicious that it has shorted turns Attached Thumbnails __________________ - Julian It's good here

24th Jan 2021, 1:58 pm	#8
Julesomega Octode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 1,085	Re: Any ID on this inductor please? I must correct my last post: the inductor is tapped. The former broke up as I removed it so I don't know how the two turns were connected, but it may have had a lot more inductance with the turns in series Oh, btw, I do love this android app Magnifier Plus, it's better than a loupe for seeing small details, plus you can save the images Attached Thumbnails __________________ - Julian It's good here

24th Jan 2021, 2:12 pm	#9
Julesomega Octode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 1,085	Re: Any ID on this inductor please? More on this inductor: the core has a much greater air (glue) gap than the others, about 0.2mm compared with a layer of thin superglue on the others. From this I conclude that it was for a smps operating at high frequency, and nothing to do with RFI suppression __________________ - Julian It's good here

30th Jan 2021, 10:05 am	#11
Jon_G4MDC Octode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 1,143	Re: Any ID on this inductor please? Agreed, that magnifier is really useful. No more done with the inductor but thanks for all the inputs.