Washing your RF front ends? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: December 23, 2020, 01:03:59 pm
content: Because even a small amount of grease or flux, can dramatically impact the RF front end of a receiver, I think they should be removable or washable or sealed tightly. Especially if you cook nearby.After some time, if your LNA is open, like everything else, it needs to be cleaned every once in a while.Is this unreasonable? I don't think so. Conformal coating might help seal them.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 23, 2020, 01:43:44 pm
content: hmm, I like cooking and I'm used to do it every day, but it never happened so far, that I had RF components nearby when e.g. frying.do you live so limited in space, that the workbench share radio and cooking activities?if you're not into microwave radio activities, so >1GHz, some flux is no bigger problem; but certainly it makes sense to not have every kind of cooking residue in your electronics.

author: coppercone2
author_rank: Super Contributor
timestamp: December 23, 2020, 04:09:48 pm
content: 50:50 distilled water alcohol mixture in spray bottle that has a good spray adjustment ($6 or so)thats the rinse, for getting rid of flux you know i acutally find it hard to beat the flux remover from MG chemicals even compared to things I have tried like simmering in a pan of pure IPA lolits like actually good, the only problem it has is that it does not have high pressure, so usually you soften it up with that, rinse off as much as possible, then blast it with a high powered IPA spray (from a can) to push everything off. When its already reasonably defluxed and you are just cleaning up something that looks pretty clean, not from flux, use the alcohol/water spray mixture. The spray bottle does not have the flushing force of a IPA spray areosol but its much cheaper and mild pressure is fine since you are not blasting away tons of crud.Products sold as flush generally have a high pressure, but this does not mean they have great chemical action. the flux remover does not really spray like a cannon but it dissolves it super well.. so you need to use both products I think, at least for the FIRST clean.Now contact cleaner flush is one thing but I think that its not necessary for PCB post-flux remover cleaning, so you can use IPA for that, then save contact flush for actual contacts. Flush = more mechanical. Deoxit sells a flush, and deoxit spray CAN be used as a weak flush, but its pretty crappy pressure compared to a real flush can (not entirely appropriate).Keep in mind with a front end overload having a bunch of crap there is more stuff to turn into carbon and make replacement and cleanup more difficult and possibly damage the PCB more.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 23, 2020, 05:04:14 pm
content: Quote from: HB9EVI on December 23, 2020, 01:43:44 pmThere sure was every kind of cooking residue in the electronics here yesterday when I powered up the bias supply in an old tube amp,after I had installed the rectifier the wrong way around, Both electros deposited their lunch in a spectacular way.

author: coppercone2
author_rank: Super Contributor
timestamp: December 23, 2020, 05:52:28 pm
content: what is safe dishwasher soap for that kind of stuff anyway? I have washed hardware I don't really care about with a dash of simple green before but I am sure there is a better specialty product (alnox series?)I think I did one tube board with the tubes removed because it was like ultra bad. Not for flux, just cleaning em, but with minimum oxidation

author: cdev
author_rank: Super Contributor
timestamp: December 23, 2020, 05:59:07 pm
content: Right now I actually am using my kitchen table when I solder, but that is not permanent, and none of my RF stuff lives in the kitchen. However, over a space of years, things get dirty and there is residue that sometimes is left after soldering. Ive noticed that when flux residue is left on things that are active gain blocks (RF front ends, LNAs, the outward looking part of receivers) being squeaky clean matters a lot. Its also impossible to get the residue off without some kind of deep cleaning and a powerful degreaser. The orange stuff I have works well. Just one drop of it. And then rinse in distilled (deionized) water.Quote from: HB9EVI on December 23, 2020, 01:43:44 pmActually, the way I judge if something like what I am describing is working is by seeing how it works >1GHz.As that's the best test. Sorry if I did not make that clear enough

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 23, 2020, 06:19:21 pm
content: from my experience things start to behave in different ways between 70cm and 23cm; what works flawlessly on 70cm, doesn't work anymore on 23cm like it would be expected.if we are talking about impedance mismatch due to residues, a proper measurement is going to answer it.flux residue is easily removed with IPA; rinse with water is imho not needed.for stronger dirt or oxidation I use brake cleanser or contact cleaner, but this has to be rinsed after, IPA is again my friend for that.

author: radiolistener
author_rank: Super Contributor
timestamp: December 24, 2020, 12:21:41 am
content: I'm using 96% ethanol to clean RF connectors and PCB.

author: bdunham7
author_rank: Super Contributor
timestamp: December 24, 2020, 12:35:22 am
content: Since you apparently have your RF gear in the kitchen anyway, you could just put it in the dishwasher.https://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

author: m3vuv
author_rank: Super Contributor
timestamp: December 29, 2020, 01:16:47 pm
content: does beer work?

author: cdev
author_rank: Super Contributor
timestamp: December 29, 2020, 01:37:18 pm
content: I think that I explained that I don't keep it in the kitchen, or use it in the kitchen.Sometimes, I use my kitchen table as a work surface. (because its a large, clean, flat and uncluttered surface well provided with lighting and power.)I asked a pretty basic question about cleaning off PCBs. It seems as if low noise amplifiers should be encased in a sealed box.Above a few hundred MHz, if a gain element, like an LNA is involved, the effect of some kinds of grime is quite noticeable - with a weak signal.Quote from: bdunham7 on December 24, 2020, 12:35:22 amSorry, don't keep any RF gear in the kitchen, although once in a while I have been known to place a mag mount antenna on top of the refrigerator since its a large handy piece of metal that makes a decent ground plane.I don't have, or want, a dishwasher right now. (also don't have enough room for one)An ultrasonic cleaner would be useful. I'd probably put it in the laundry area.

author: cdev
author_rank: Super Contributor
timestamp: December 29, 2020, 01:53:24 pm
content: No, the salt of the residue left by beer(https://en.wikipedia.org/wiki/Pyroglutamic_acid)is particularly hydrophilic, to the point where its used as a skin moisturizer. Being a salt its also conductive when wet.It's probably the reason why many feel that moderate beer consumption is good for the brain.(To some extent it even counteracts the deleterious effects of alcohol.)Quote from: m3vuv on December 29, 2020, 01:16:47 pmSo, no.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 29, 2020, 03:13:46 pm
content: The electrical line workers use wipes and sprays to clean the hot sticks before use.It is used to prepare the frp hot stick, providing a high surface resistance against tracking when the end is on the high voltage.I have some to clean the old electronic stuff, ..pots and contacts too..Search "hot stick cleaner"

author: cdev
author_rank: Super Contributor
timestamp: December 29, 2020, 08:18:58 pm
content: I usually use IPA and foam swabs, but some kinds of solder flux residue don't come off completely with IPA without some additional physical motion and it seems something like this orange cleaner and water which is a degreaser. And something like a toothbrush is helpful too.

author: rfclown
author_rank: Frequent Contributor
timestamp: December 29, 2020, 09:59:53 pm
content: If it's something for myself, I almost never clean. I usually only clean stuff that I'm sending out. I was reading this thread and saw that someone had used IPA. I realized that I had never even thought of using IPA. I happened to have one open, so I thought I'd try it. I grabbed a board on my bench that I had soldered recently, a USB to serial converter that I had to solder on a 100 mil header. I took a before picture. Then I tried a swab with IPA. It didn't work very well. Took picture. Then I used 99% isoproply alcohol with a swab, then brushed (my usual practice if I'm cleaning), and it cleaned up well. The isoproply bottle in the picture says 70%, but what's inside is 99%. The IPA is 7.5%.

author: cdev
author_rank: Super Contributor
timestamp: December 29, 2020, 10:08:14 pm
content: Yes, that's the stuff that some fluxes leave behind for me too. I don't mind cleaning it off. Like most people I don't care about it much of the time. In my experience neither 70% nor 90% ipa gets it off completely. I have to use a degreaser - and water, I usually use distilled water, and then another rinse with that. I don't have 99% ipa, I just get my supplies when shopping, usually. I am sure I could find it, just havent. I have a gallon of this degreaser, which I am sure will last me my whole life. Because its so strong just a drop or so is needed. Its a citrus degreaser.I think the issue that I see has something to do with the DC used to power the MMICs I typically use.Its probably present in other electronics too, but whatever current is involved there - it must be small.