a kind of diode? - Page 1
Forum section: electronics / beginners

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 12:18:20 am
content: Hi, a cylindrical diode shaped component of one color deep grey.There is two of these on this TV model LED board. I removed both from the board, please look at the photos.Because I could not identify these components I measured them as diodes because they look like diodes and the grey colored one when measured @ mVs after settling down from readings going up and down is 0.13V both ways, and the blackened one measures 0.12V one way and 0.14V the other way and later when I measured the readings kept jumping between 0.23V and 0.14V.Can someone tell me what these components are for replacement please.This 50 inch LED TV Board is model TNP4G549 - S01A 549AA A11457JZ 130719 < all the numbers I do not find a result for on GoogleIn the second photo is both which seems to be one good component, and the burned (blacker) component both seeming to be the same kind with no markings whatsoever on both.

author: chris_leyson
author_rank: Super Contributor
timestamp: November 28, 2018, 12:27:42 am
content: Small radial sheilded inductors, maybe something like thesehttps://katalog.we-online.de/en/pbs/WE-TIS. They're marked L9804 and L9805 on the silkscreen.

author: xavier60
author_rank: Super Contributor
timestamp: November 28, 2018, 12:37:27 am
content: The middle holes look too clean to have had a lead in them. Ferrite beads on leads placed in the outer holes maybe.Need to see the other side.And show us the parts.

author: gamalot
author_rank: Super Contributor
timestamp: November 28, 2018, 01:03:07 am
content: Didn't see anything looks like diode, where are they?OK, they look like ferrite beads.

author: xavier60
author_rank: Super Contributor
timestamp: November 28, 2018, 01:05:08 am
content: There are many photos of very similar appearing boards. The parts do look much like beads to me.https://www.google.com.au/search?client=opera&hs=C9q&biw=1280&bih=669&tbm=isch&sa=1&ei=Dej9W5TYHcqLvQTB6r7gCQ&q=TNP4G549++-++&oq=TNP4G549++-++&gs_l=img.12...3109.3109..5264...0.0..0.213.213.2-1......1....1..gws-wiz-img.ASL1WJdnadg#imgrc=z4-rqH-wEp8ICM:

author: xavier60
author_rank: Super Contributor
timestamp: November 28, 2018, 01:38:44 am
content: Even though they may have been running hot, which can be normal, there will be nothing wrong with them.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 01:53:50 am
content: Reply to all - thank you for the feedback. I think I have found these to be Axial Ferrite beads inductors, and I have no idea how to find a value to test the two I have although they measured at 0.13V and all the ones I can see on ebay are all larger than these. Can someone tell me how to test these... meanwhile I will go check on how to do this myself.I can not upload anymore photos, so maybe if needed I can remove what I have posted and post some more. Or I could resize all my photos for this, but not sure if they are going to be too small to view then.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 01:55:17 am
content: I do get different readings from both and strongly suspect the blackened one has been damaged. The burn mark on the board is telling me this.

author: dmills
author_rank: Super Contributor
timestamp: November 28, 2018, 02:04:12 am
content: While you can never say never, damage is very, very unlikely, them things are about as reliable as anything gets.The heat is probably from the devices under those two heatsinks, and cheap ass paxolin board does discolour at a fairly low temperature by the standards of modern power semiconductors.Regards, Dan.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 02:08:01 am
content: For some reason this LED TV thrown away with a severely smashed up screen and 6 of all of the LEDs on the led backboard are not working so I suspected the damaged appearance of the blackening on the LED driver board.I think i should replace both of them because they are giving different fluctuations while testing but i am not sure what values i need to look at.

author: helius
author_rank: Super Contributor
timestamp: November 28, 2018, 02:12:08 am
content: Inductance measurement is a feature of some DMMs, and all LCR meters (including the cheap "ESR02" units based onthis thread). Small ferrites like those are usually around .1 to 4 millihenries or mH.I agree with others who said that these barely ever fail. It's literally a wire with a chunk of iron oxide around it. The only reason to replace them would be if they are grossly cracked or corroded.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 02:26:08 am
content: Thank you the information.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 03:58:36 am
content: I am using a UNI-T 61E. What would I use n my meter to measure millihenries or measure anything like millihenries? I am thinking measure M Ohms at a guess. Wikipedia did not appear to be especially informative about a comparison in values that i could understand. I forgot to mention, if i found nothing wrong with these Axial Ferrite beads inductors I would remove and test the transistors.

author: xavier60
author_rank: Super Contributor
timestamp: November 28, 2018, 05:45:41 am
content: You have not given your age. If you are young, it would be best to research some basic electronics first.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 11:23:20 am
content: I am old and thank you for the tip, I will continue research.

author: perieanuo
author_rank: Frequent Contributor
timestamp: November 28, 2018, 12:19:19 pm
content: It's a choke, measures almost short-circuit, if not just put a wire instead.Regards,PierreEnvoyé de mon iPad en utilisant Tapatalk

author: GeoffreyF
author_rank: Regular Contributor
timestamp: November 28, 2018, 01:18:50 pm
content: It is a wire with a ferrite bead on it. As such it is a choke. With an ohm meter DC resistance will be the leads + that wire. At some high frequency, there will be reactive resistance. The purpose of these in a circuit is usually to prevent spurious high frequencies moving from one part of the circuit to another.If you ever have seen these mysterious warts around wires going to or from a computer, these are larger chokes and serve the same purpose.You will likely realize that these beads can move freely around the wire.There is no concern about heat damaging these devices unless it is literal flame. If they are hot, it may be that another part of the circuit (or a nearby transmitter) is generating high frequencies that are outside design parameters.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 08:14:40 pm
content: Thank you, i think you have summed the problem up here and I will be removing the transistors about the burned area to test them. I actually want to use the LED panel from this TV, to experiment the use of an overhead LED light for my workbench. Just for fun at this stage. Thank you.I think replacing both of the ferrites is a good idea because of the erratic readings when testing.The blackened one reading more inconsistently than the greyer colored ferrite.

author: xavier60
author_rank: Super Contributor
timestamp: November 28, 2018, 10:51:46 pm
content: The erratic reading is just because of the surface corrosion on the leads.

author: nickeevblog10
author_rank: Contributor
timestamp: November 28, 2018, 11:21:14 pm
content: oh wow, thank you for that, I will clean them and retest soon,*** thank you very much Have a Good Christmas!

author: nickeevblog10
author_rank: Contributor
timestamp: December 01, 2018, 08:23:13 pm
content: Having not tested the ferrites without cleaning the lads so readings are unaffected b dirty leads, would replacing the ferrites with a larger ferrite be as effective as the same size ferrite?I just thought to ask. I just looked at Dave Turners recent post about ferrite beads and thought it interesting to see more information about the use of ferrites in circuits on pcb boards, and before cleaning the leads on the ferrites I wastesting I had thouight to replace these two on this board andcould only find larger ferrites overall by about 2mm.

author: xavier60
author_rank: Super Contributor
timestamp: December 01, 2018, 09:57:37 pm
content: Another option is to replace the wire. That is if it has been glued into the bead.Make sure that the old wire is straight and burr free.While holding the wire with pliers, use your iron to apply fresh solder to the wire near the bead for good heat transfer to melt the glue then slide the bead off with the tip. Don't use pliers on the bead, it will break.The best option is to put the beads back as they are. There is nothing wrong with them.

author: nickeevblog10
author_rank: Contributor
timestamp: December 01, 2018, 11:44:57 pm
content: After a gentle scraping with a copper wire brush and retesting the readings are much more stable. There is no more erratic fluctuations in the readings.So these two will be going back on to the board and now I am going to remove and test the black square black 3 pin components surrounding the two ferrites.I think there is 5 there and not sure what kind of components they are.