Help with finding a part or a substitute. - Page 1
Forum section: electronics / repair

author: cryptlabs
author_rank: Contributor
timestamp: February 22, 2019, 12:09:54 pm
content: HelloI'm trying to fix a Radio transceiver and found a blown damaged part inside. I have tried to source and buy this part without any luck.The part is :wbrh-35908 Ferrite BeadsIt's from this manufacturer :http://www.3lcoil.com/files/down-products%20list.pdfWhat part should i order from Digikey that will work the same ?RegardsSent from my ONEPLUS A5010 using Tapatalk

author: bob91343
author_rank: Super Contributor
timestamp: February 22, 2019, 08:26:00 pm
content: The characteristics are in the link. It's definitely not a critical part; ferrite beads seldom are. It's in there just to keep the signal clean and you can probably use nearly any small bead with no problem. It says 10 Ohms at 25 MHz so look for that, along with approximate dimensions and you'd be fine.

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 22, 2019, 08:46:56 pm
content: Ferrite Beads don't fail, do you have a picture?

author: cryptlabs
author_rank: Contributor
timestamp: February 22, 2019, 08:50:02 pm
content: Quote from: PA0PBZ on February 22, 2019, 08:46:56 pmYes, it exploded because of a faulty shorted transistor that was connected in series right after it. It melted the conductor inside the ferrite bead.Regards

author: cryptlabs
author_rank: Contributor
timestamp: February 22, 2019, 08:54:06 pm
content: Quote from: bob91343 on February 22, 2019, 08:26:00 pmThanks for the reply, it says 60 ohms at 25mhz and 80 ohms at 100mhz.I would like to get something really similar. I'll try to search on Digikey.RegardsRegards

author: wraper
author_rank: Unknown
timestamp: February 22, 2019, 08:55:44 pm
content: Just buy any 80R coil of the same size and current rating not lower than original. They are parts with pretty loose spec to begin with.

author: cryptlabs
author_rank: Contributor
timestamp: February 23, 2019, 06:29:00 am
content: Can someone please suggest a part number ?Regards

author: DaJMasta
author_rank: Super Contributor
timestamp: February 23, 2019, 08:35:25 am
content: Are you *really* sure it was the ferrite that was damaged? 60 ohms at 25MHz with a through hole part has gotta be rated for many amps, and it's literally just a wire through the center of a ferrite material.I would suspect virtually any part around it before I suspected the ferrite, though there is some slim chance it could be the fault. I would suspect a schematic or parts not matching the implemented circuit long before I would suspect a ferrite bead exploded.If you really, really, still think it's the ferrite, then the recommendation of "any old bead" fits well. Find something that looks close to the original part and has an impedance rated in the same ballpark. You could even buy a small ferrite ring and just put it around the leg of a transistor to similar effect. It's also true that if you omitted the part in favor of a wire jumper and it was originally at fault, the device would work. Adding it in may improve noise performance somewhat, it was there for a reason initially, but there are virtually no designs where the ferrite bead when omitted can cause a total failure.

author: cryptlabs
author_rank: Contributor
timestamp: February 23, 2019, 08:39:23 am
content: Quote from: DaJMasta on February 23, 2019, 08:35:25 amYes I'm sure, it blew in front of me.I don't know why its so hard to just get an advice on an equivalent part number so i can move on with the repair.Anyway, thanks everyone.Regards

author: DaJMasta
author_rank: Super Contributor
timestamp: February 23, 2019, 08:48:47 am
content: And I think as has been said, even if it's exactly as you say, there's a whole slew of parts in the right ballpark that would make excellent substitutions.... so giving you an exact part number is tricky, especially when we don't even know what the form factor is.If it's an axial bead, how about the first cheapest one in the ballpark on digikey:https://www.digikey.com/product-detail/en/laird-signal-integrity-products/28L0138-80R-10/240-2513-2-ND/101587586 ohms impedance at 100MHz, wideband ferrite material, very low DCR

author: bob91343
author_rank: Super Contributor
timestamp: February 23, 2019, 05:21:23 pm
content: Ferrites have two common purposes. One, to reduce susceptibility to stray fields and two, to suppress parasitic oscillations.In this case, the ferrite didn't really blow. The wire inside it melted and caused damage. Knowing a little about it, I'd say leave it in the circuit as long as the conductive path still exists. The ferrite wasn't, I am sure, damaged to the point where it stops doing its job. These are make of very high temperature material.But cosmetically I understand why you want a new one. You can buy an assortment of beads for very little money and thread your own wire through. Just make sure the material is characterized for the right frequency range. Look in a distributor catalog for ferrite beads and buy a bag of them of various sizes. It might be called a kit or an assortment. Put one in that is no smaller than the original, else thread two or more over the wire.

author: cryptlabs
author_rank: Contributor
timestamp: February 23, 2019, 05:33:16 pm
content: Quote from: DaJMasta on February 23, 2019, 08:48:47 amI have included the link to the original part pdf.It looks like a black resistor almost.The inductor is in yellow.The shorted transistor which i think blowed the inductor is in red.Regards

author: bob91343
author_rank: Super Contributor
timestamp: February 23, 2019, 05:55:07 pm
content: That is an interesting circuit with no dc path for emitter current. Is the capacitor C219 good? Or perhaps there is an error in the diagram.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 23, 2019, 06:49:37 pm
content: VSB or something! Hard to imagine blowing a ferrite bead with the RF power of a TIP36C

author: bob91343
author_rank: Super Contributor
timestamp: February 23, 2019, 07:16:38 pm
content: Yes I believe it's 5V or something. So that's the source. I see it now.So my conclusions haven't changed. Just replace it with something similar and be done with the problem.

author: DaJMasta
author_rank: Super Contributor
timestamp: February 23, 2019, 09:17:00 pm
content: Quote from: cryptlabs on February 23, 2019, 05:33:16 pmThen the part I linked would be plenty suitable, you just probably want single quantity and not a reel of 4500 (so it's 10 cents each instead of 2.5 cents each). That said, any similar looking axial ferrite from ebay or aliexpress would likely be fine..... as would just a jumper link. The one I linked is pretty similar to both specified impedances of the original part (a tad low at 25MHz, a tad high at 100MHz), but as many have said, it's really not super important for this application.

author: bob91343
author_rank: Super Contributor
timestamp: February 23, 2019, 11:23:25 pm
content: Sure, All Electronics would have something. Too bad the day of over-the-counter electronics parts stores is largely gone. Most have minimum orders and charge exorbitant prices for shipping. The bottom line is always money.

author: cryptlabs
author_rank: Contributor
timestamp: February 24, 2019, 07:07:12 am
content: Quote from: DaJMasta on February 23, 2019, 09:17:00 pmThanks Bro, I'll try to order that one.And thanks to everyone else also.The radio is a Lincoln II , this is the full schematics link.http://www.radiomanual.info/schemi/Vari/President_Lincoln-2_sch_V3.pdfThe radio stopped Tx only Rx. I have opened the radio to check and when i Txed that inductor blew up with a spark but looks fine from outside.I then checked the Transistor and it was checking bad.So i hope replacing the Inductor and Transistor will bring it back.Regards

author: yodisty
author_rank: Newbie
timestamp: February 24, 2019, 09:31:04 am
content: I'm alpha testing a new cross reference tool (not released to public). This (attached) is what it gave me along with a bunch of others.Any feedback on what you see in the screen is useful as i can feed it back to the product developers

author: cryptlabs
author_rank: Contributor
timestamp: February 24, 2019, 03:03:41 pm
content: Quote from: yodisty on February 24, 2019, 09:31:04 amThe image is kind of blurry.Regards

author: yodisty
author_rank: Newbie
timestamp: February 24, 2019, 04:36:44 pm
content: Hmmm, just a standard mac screen capture. Possibly the upload changed it here? or you have your browser zoomed slightly by default?Anyhow the suggestion was that the actual part number is WBRH-3.5X9X0.8 and there are several very close parametric matches.FBA04HA900AB-00 - Taiyo YudenFBA04HA900BB-00 - Taiyo Yuden7427606 - Wurth Elektronik Gmbhetc..

author: cryptlabs
author_rank: Contributor
timestamp: February 24, 2019, 05:10:48 pm
content: Quote from: yodisty on February 24, 2019, 04:36:44 pmMaybe because I'm viewing the attached file on a a smartphone.Anyhow, excellent!I'll try to search for the part on Digikey.Regards

author: cryptlabs
author_rank: Contributor
timestamp: February 25, 2019, 12:49:37 pm
content: Quote from: yodisty on February 24, 2019, 04:36:44 pmI have searched for the parts, most are obsolete.Regards

author: cryptlabs
author_rank: Contributor
timestamp: February 28, 2019, 06:51:48 am
content: Will this work ?https://www.mouser.com/access/?pn=623-2743015112&sn=623-2743015112&utm_source=mouserandroidapp&utm_medium=app&utm_campaign=623-2743015112&utm_content=Fair-RiteRegards

author: DaJMasta
author_rank: Super Contributor
timestamp: February 28, 2019, 07:58:00 am
content: Should be fine, as many others.

author: cryptlabs
author_rank: Contributor
timestamp: February 28, 2019, 08:04:12 am
content: Quote from: DaJMasta on February 28, 2019, 07:58:00 amCool, thanks bro.Hope the radio gets fixed.Regards