Fake PN4391 JFETs from eBay - Page 1
Forum section: electronics / projects

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 26, 2025, 06:10:50 pm
content: Hi group,I was stocking up on N. Channel JFETs. These are often used in metrology equipment as analog switches.I have bought from three different eBay vendors. Two supplied parts marked like this:These test as NPN transistors.I have left neutral feedback for one vendor. He offered a full refund immediately.I have requested a refund from vendor 2.The third vendor supplied good parts with Siliconix markings.Regards,Jay_Diddy_B

author: edavid
author_rank: Super Contributor
timestamp: September 26, 2025, 06:39:43 pm
content: Don't leave us in suspense, tell us the good vendor!

author: thm_w
author_rank: Super Contributor
timestamp: September 26, 2025, 08:57:05 pm
content: Those markings look identical to these:https://www.aliexpress.com/item/1005008786670592.htmlBut these are different:https://www.aliexpress.com/item/1005008536117818.html

author: edavid
author_rank: Super Contributor
timestamp: September 26, 2025, 10:38:48 pm
content: Quote from: thm_w on September 26, 2025, 08:57:05 pmIf you are going to pay that much, you might as well buy real parts from Mouserhttps://www.mouser.com/ProductDetail/Central-Semiconductor/PN4391-PBFREE

author: thm_w
author_rank: Super Contributor
timestamp: September 26, 2025, 11:03:37 pm
content: Quote from: edavid on September 26, 2025, 10:38:48 pmNot sure why OP is buying on ebay then, I wouldnt even bother.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: September 26, 2025, 11:13:29 pm
content: edavid and thm_w,Thank you for the pointer to Mouser. I had only looked at Digikey.Jay_Diddy_B

author: floobydust
author_rank: Super Contributor
timestamp: September 27, 2025, 02:03:44 am
content: Linear SystemsandInterfetmake JFETs and are available from Digi-Key and Mouser.During the chip shortages in 2023, there were no JFETs to be found and I ordered from Aliexpress.Good: Fantasy Electronics CO., LtdStore no.: 1911309It seems to be a sub-store of VANXYBad: shenzhen IC storeStore no.:1949429The JFET's had very high IDSS, as if out of spec rejects or possibly just a lump of coal in there lol. The parts looked rough.Hard to know, their store logo is on many ads and "IGMOPNRQ" is also on them, no idea what that means.I think many vendors are next to each other in SEG Plaza and just hand parts to each other as needed.

author: Smokey
author_rank: Super Contributor
timestamp: September 27, 2025, 02:28:31 am
content: Sorry for being "that guy", but I know you know better than to source parts from ebay/aliexpress/amazon/shenzen-market places.The surprise should be if you actually DO get real good useable parts.

author: floobydust
author_rank: Super Contributor
timestamp: September 27, 2025, 02:41:10 am
content: People shop for the lowest possible price, which is the mistake.If they're priced below the majority of stores, it's for a reason- which is obvious to the Chinese, that the part has quality issues.This is what I've learned and buying a notch above the aquarium bottom, I have way less problems.Parts from Shenzhen booths are fine, if you're in the country.

author: Haenk
author_rank: Super Contributor
timestamp: September 27, 2025, 06:18:11 am
content: Consider buying directly from Taobao (via shipping agents) - vendors with good standing ratings in the hundreds of thousands are very unlikely to sell you faked goods.Rare and sought after items will not be cheap though.However - they do have a different pricing strategy compared to our distributors. You often only need a handful of pieces, which puts you in the "10x as expensive as the 10000 price)" - the larger chinese sellers however often offer a sales price based on the lowest price segment, combined with low shipping costs, that might reduces costs quite a lot. Of course that is only good for private use, when you don't need just-in-time delivery or proof of sourcing.Buying from Aliexpress is more like a gamble, it seems.