Replacement Inductor - Page 1
Forum section: electronics / projects

author: kosm
author_rank: Newbie
timestamp: July 13, 2017, 08:52:06 pm
content: Hey guys!I am currently working on a project and I require on building a pulser that pulses with nanosecond-picosecond width. I've just soldered Jim William's original circuit which can be found here on page 21:http://cds.linear.com/docs/en/application-note/an61fa.pdfSo my problem right now is that the inductor L1 can't be found anywhere (it's virtually inexistent now), and I was wondering if you guys can help me and suggest a replacement one that is available to buy. I used a regular 820u inductor and it heats up fast, and the output voltage it gives is 20V instead of the 70 V needed.Thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 14, 2017, 12:23:58 am
content: Spec'd part is 820uH, 22DCR, 150mA.What exactly was a "regular 820u inductor"?Tim

author: kosm
author_rank: Newbie
timestamp: July 14, 2017, 07:32:10 am
content: omg thank you! you are a life saver. Well I just thought of using any 820uH inductor I could find, lol. Where did you get those specs though? Do you have a datasheet or something for it? Problem now is that I'm looking for inductors with the same specs and it seems that electronics store only sell them in bulk of 1000+ which costs ~$1, lol.Thanks a lot man!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 14, 2017, 11:36:31 am
content: Sometimes you'll run across old datasheets or catalogs on the web, this happened to turn up:http://www.eolpartfinder.com/eolpartdetail.php?q=100267&Brand=JW+MILLER+MAGNETICSHave you looked at Digikey or Mouser?Mind that each of the specs can be a range. DCR <= 30 ohm should be no problem. Current rating will be kind of all over the place, can say 100mA and up. Inductance probably not critical either, maybe 680 to 1000uH.Should return hundreds to choose from. Refine further by package (thru-hole or SMT, and size and shape), stocking and packaging (usually cut tape and bulk), and price, and you should still have a couple to pick from.Tim

author: kosm
author_rank: Newbie
timestamp: July 14, 2017, 08:38:56 pm
content: Thanks a lot man!! You've saved meI'll try looking around from your suggestion. I looked through digikey with the specific specs and they only do it in bulk. I'll try what you've suggested.Thanks a lot again!

author: kosm
author_rank: Newbie
timestamp: July 21, 2017, 08:56:57 pm
content: Hi!So I've tested a couple of inductors and 1 of them had the same problem of heating up fast (DCR=12 ohm, 820uH, 140mA) and then I used a different one (DCR=1.98 ohm, 820 uH, 420 mA) and it doesn't heat up anymore but the LT1082 now heats up. The voltage output I needed seem to be good, but the chip just heats up and the current it sucks in is too high (goes to close to 1A). Can you help me with this problem?

author: MK
author_rank: Regular Contributor
timestamp: July 22, 2017, 08:10:15 am
content: what happens to the bias voltage when it heats up, is too much power trying to be delivered somewhere else? shorted cap or Q1 is shorted perhaps?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 22, 2017, 10:16:21 am
content: Sounds like it's being overloaded, or it's not wired or laid out correctly.Tim

author: kosm
author_rank: Newbie
timestamp: July 24, 2017, 07:52:43 pm
content: Hi! thanks for the replies. I've checked the circuit many times and had it rechecked by someone else and it seems to be correct. The Q1 works fine as I removed it and tested the pulser circuit all by itself.