Sourcing feedthrough capacitors - insane prices? WTF?! - Page 1
Forum section: electronics / rf-microwave

author: Yansi
author_rank: Super Contributor
timestamp: June 02, 2018, 10:42:25 am
content: Helloworking on some of my projects, I'd like to use a few feedthrough capacitors in and out of an enclosure. To obtain better manufacturing repeatability, I decided to source new ones.I am absolutely stunned by the insane prices they go forIs this really normal? It is not that rare to find an Ebay or Aliexpress sale where a piece (a single fucking piece!) goes like for GBP 3+ or $ 10+. Are you f. kidding me? That is just crazy!I find even a single $ for such thing to be a rip off. Is this really their normal price today, or am I just dumb to find them for a reasonable price? My idea of the price was originally like 25 cents a pop.Do you have any experience sourcing these? I am looking for a small ones, low voltage, low current (amp or two maximum). Capacitance should not play a big role here. I am looking for the type that screws into the wall of the enclosure (preferably metric thread, but seems like I am expecting too much).I couldn't find any of these at Mouser or any distributors. Are they still being made?

author: Rerouter
author_rank: Super Contributor
timestamp: June 02, 2018, 10:58:29 am
content: Everywhere i just looked was popping them up at above $8 for the screw threaded kind, smd ones seem much cheaper, If your intention is there filtering effect, which could then be combined with a DC feedthrough of the same shape (where I looked had "ask us" pricing, however there construction would seem cheaper

author: yl3akb
author_rank: Regular Contributor
timestamp: June 02, 2018, 11:00:51 am
content: I usually buy them here. Solderable, without thread are quite affordable:https://www.rf-microwave.com/en/panel-mount-capacitors-emi-filters/183/Mouser also have quite a large supply of them:https://eu.mouser.com/Passive-Components/EMI-Filters-EMI-Suppression/EMI-Feedthrough-Filters/_/N-bw7oz/?Ns=Pricing|0

author: Yansi
author_rank: Super Contributor
timestamp: June 02, 2018, 11:26:10 am
content: I need those with thread. The enclosure is aluminum. (I know aluminium can be welded even soldered, but trust me, I do not want to attempt that here).

author: bd139
author_rank: Super Contributor
timestamp: June 02, 2018, 11:34:19 am
content: There’s a guy in the U.K. that sells 25 for £7.99 + delivery. They’re 10nF and tiny but work nicely and will take an amp or so. Not screw but solder in. I’m using copper sheet for RF enclosures so they work nicely.Gave up on screw ones due to the price.

author: yl3akb
author_rank: Regular Contributor
timestamp: June 02, 2018, 02:04:22 pm
content: Quote from: Yansi on June 02, 2018, 11:26:10 amRecently I bought these:https://www.ebay.com/itm/1500-pF-1-5-nF-400-V-LOT-OF-10-Shp-RUSSIAN-CERAMIC-FEEDTHROUGH-CAPACITORS/272980333547?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649They are unused old Russian made components and feel quite good quality. Leads are little bit oxidized, but no issues with soldering. Very fast shipping also (within EU at least).

author: Yansi
author_rank: Super Contributor
timestamp: June 02, 2018, 02:43:34 pm
content: I have dug from bottom to top to bottom through my garbage piles and found five of these specimens. Nice! At least something to start with. The thread is M4x0.5 (fine pitch metric) but not an issue. Better than some imperial fraction of whatever body part.I will search through ebay more thoroughly, but the prices are insane anyway.I think these are russian too, but not sure. I have no problem with that.

author: CopperCone
author_rank: Super Contributor
timestamp: June 02, 2018, 02:51:31 pm
content: When I gutted my spectrum analyzer that had over like 4 faults and some unrepairable stuff like bad ROMs and fried RF cards, I took the power feedthroughts out of the can. I realized that with all the feed through s I removed, I basically saved enough money to cover my repair attempt costs.Soldering or brazing aluminum is horrible. I don't mind gas welding it. But I have basically gotten nothing but grief with aluminum. If you dremel the crap out of a surface, use the special aluminum solder and flux (which smells like complete poison), you can get a joint, but it will look like shit.Brazing is the worst though. Eventually I managed to pull some decent joints but it seemed basically random as to if it will wick. I need to try doing a hydrochloric acid clean some time before attempting the braze.A wire or something is not that bad, but soldering to a large surface, just to do some sheets, I needed to use like a 150W iron.

author: Co6aka
author_rank: Unknown
timestamp: June 12, 2018, 11:32:15 pm
content: Would these be of any use?https://www.ebay.com/itm/142831467569

author: Cerebus
author_rank: Super Contributor
timestamp: June 13, 2018, 12:40:30 am
content: Quote from: yl3akb on June 02, 2018, 02:04:22 pmOften the Russian stuff has silver plating. On old stock it lookshorrible, but a quick dip into the other half's "silver dip" jewellery cleaner and a rinse in deionised water and you have a shiny new looking component.

author: Ian.M
author_rank: Super Contributor
timestamp: June 13, 2018, 02:16:56 am
content: For a hobby project, I'd probably just put copper tape with conductive adhesive on both the inside and outside of the aluminum enclosure, and use the solder-in type.

author: Yansi
author_rank: Super Contributor
timestamp: June 13, 2018, 09:46:10 am
content: That would be ugly. I'd better buy a few pieces of the overpriced ones.I will try searching through some local NOS suppliers. Maybe some of them will make acceptable offers.

author: Ian.M
author_rank: Super Contributor
timestamp: June 13, 2018, 10:02:21 am
content: Feedthrough capacitors are ugly anyway. Another alternative would be to bend up a flanged five sided screening can from tin plated mild steel sheet with soldered seams, fit solder in feedthroughs to that, and bolt its flanges to the inside of the enclosure with copper braid as a conductive crush gasket. Then you can mount connectors or use cable grommets on that part of the enclosure panel that will be covered by the screening can. The only external evidence of its presence would be the lines of screw heads bolting its flanges down.

author: bd139
author_rank: Super Contributor
timestamp: June 13, 2018, 10:08:23 am
content: Also d-sub nWn connectors are quite neat for one offs. You can solder decoupling caps across the pins if you want and bring everything out of the same hole. When the connector shell is mated to it, it's RF tight. Not as good as a real feed through but solves a lot of problems in one go.

author: Yansi
author_rank: Super Contributor
timestamp: June 13, 2018, 10:51:52 am
content: Soldered hacktogether tin can is nice, I use them for prototypes. But it is still ugly, compared to a nice milled aluminium enclosure.Fitting any connectors to the milled enclosure is a pain, as it is veeery small one: Just 61x44x12mm. The Dsub nWn you pictured is larger than the enclosure itself)However I think these coaxial d-Subs are extremely expensive, to my best knowledge.

author: Wolfgang
author_rank: Super Contributor
timestamp: August 15, 2018, 08:57:32 pm
content: Hi,threaded feed-thru caps are expensive, but the solder-in ones are quite cheap. I bought mine from Oppermann Electronic in Germany.

author: metrologist
author_rank: Super Contributor
timestamp: August 15, 2018, 09:43:43 pm
content: Can you take the solder in ones and solder them into drilled brass screws? Is there conductive epoxies that could glue them in place?

author: Wolfgang
author_rank: Super Contributor
timestamp: August 15, 2018, 10:10:20 pm
content: I did this once. A lot of work, though, and the brass screw must be fine thread and have a 4mm bore at least.

author: whalphen
author_rank: Regular Contributor
timestamp: August 17, 2018, 06:54:23 pm
content: Solder mount is readily available and inexpensive. Consider mounting them on a copper sheet or PCB panel and then attaching the copper panel flat inside the aluminum panel with the capacitor leads extending through holes in the aluminum panel.