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whit3rd <whit3rd@gmail.com>: Nov 20 10:06PM -0800 > I have a Samlex 120VAC-13.5VDC at 35A switch mode power supply for my amateur radio equipment. Working great for last 7 years. Recently it's now producing "swooshing" noise in my radio receiver, especially on frequencies from 1.8-10MHz. Took it apart and noticed blown tops on the 3 output filter electrolytics, so I replaced those. But that did not help.   > I could replace the 2 larger input filter electrolytics but they "look" OK and...   The fast rectifiers on the low voltage side can fail/become leaky, and when they do, they can take out capacitors. Check those.

Jeff Liebermann <jeffl@cruzio.com>: Nov 20 10:29PM -0800 >I have a Samlex 120VAC-13.5VDC at 35A switch mode power supply for my amateur radio equipment. Working great for last 7 years. Recently it's now producing "swooshing" noise in my radio receiver, especially on frequencies from 1.8-10MHz. Took it apart and noticed blown tops on the 3 output filter electrolytics, so I replaced those. But that did not help.   >I could replace the 2 larger input filter electrolytics but they "look" OK and I wonder if maybe I should be thinking of also replacing the switcher MOSFET - I don't know where else the noise could be coming from?   >Any ideas greatly appreciated.   I can't tell from here where the noise is coming from. Usually, I put a small loop antenna on my spectrum analyzer and save it around the power supply while under load. That usually locates the general area.   Much more interesting is why three capacitors would decide to bulge. Bulging is usually caused by excessive ripple current through the filter capacitors. High ripple could be coming from the diodes, or simply from undersized capacitors that can't hold a charge between switching cycles and therefore draw more current than normal.   I suggest you put a scope on the output while under load and see if there's any ripple present. Compare the value with the manufactures specs. Also, use an IR thermometer to measure the case temperature of the capacitors. If they are getting warm, then there's ripple current going through them.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

"pfjw@aol.com" <pfjw@aol.com>: Nov 21 04:15AM -0800 > I have a Samlex 120VAC-13.5VDC at 35A switch mode power supply for my amateur radio equipment. Working great for last 7 years. Recently it's now producing "swooshing" noise in my radio receiver, especially on frequencies from 1.8-10MHz. Took it apart and noticed blown tops on the 3 output filter electrolytics, so I replaced those. But that did not help.   > I could replace the 2 larger input filter electrolytics but they "look" OK and I wonder if maybe I should be thinking of also replacing the switcher MOSFET - I don't know where else the noise could be coming from?   > Any ideas greatly appreciated.   a) Replace all the caps. Unless you have both X-ray eyes and an ESR meter, you have no effective way of discerning whether they are good or not. b) If it works otherwise - that is, produces the correct voltage - unlikely that the MOSFet is bad. c) It becomes a close-run thing whether the cost/time involved in repairs exceeds the value of the device if it is more than just the caps.   Peter Wieck Melrose Park, PA

Jeff Liebermann <jeffl@cruzio.com>: Nov 21 08:37AM -0800 On Sun, 20 Nov 2016 22:29:35 -0800, Jeff Liebermann <jeffl@cruzio.com> wrote:   >I can't tell from here where the noise is coming from. Usually, I put >a small loop antenna on my spectrum analyzer and save it around the >power supply while under load. That usually locates the general area.   Is this the one or is there some reason you didn't bother disclosing the model number? Notice that the SEC-1235 is a 12V 30A device and current limits at 35A. How many amps are you drawing? <http://www.samlexamerica.com/products/ProductDetail.aspx?pid=66>   See page 10 for RFI information: <http://www.samlexamerica.com/documents/manuals/11001-SEC-1235-1235M-1114.pdf>   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

ohger1s@gmail.com: Nov 21 08:46AM -0800 On Monday, November 21, 2016 at 1:29:40 AM UTC-5, Jeff Liebermann wrote:   > 150 Felker St #D http://www.LearnByDestroying.com > Santa Cruz CA 95060 http://802.11junk.com > Skype: JeffLiebermann AE6KS 831-336-2558   In the last 15 years, I've changed literally thousands of bulged electrolytics in consumer electronics for no other reason except they were just crappy parts at the end of their limited lifetimes. Most of those that bulge or vent are higher value types, say those beyond 330uf or so. Smaller electros fail at the same rate of their big brothers but don't generally visually vent. In the old days, capacitors didn't bulge unless they were tortured. Today it's mediocre chemistry that causes this, not circuit issues.   If you were to take apart 10 working flat screen TVs made in the last few years, half of them would show some sign of bulged or top vented capacitors despite running normally.

Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Nov 21 07:15AM +0100 On 21.11.16 5:50, bitrex wrote: >> loudly, and start over, but this time slide the back cover on the cable >> *first*!   > Yes. I am guilty of this. :-(   It happens most often with 100pins amphenol connectors.(dont ask me how I know....)

mjb@signal11.invalid (Mike): Nov 21 11:16AM In article <N2vYz.67146$lI2.43178@fx39.iad>, >> loudly, and start over, but this time slide the back cover on the cable >> *first*!   >Yes. I am guilty of this. :-(   Now you may progress to Stage 2 Error: Remembering to put the shroud on, then discovering you put it on backwards ... -- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

N_Cook <diverse@tcp.co.uk>: Nov 21 08:07AM On 17/11/2016 14:21, N_Cook wrote: > cooked and melted relay case , so the contact is permanently closed, > explains the switch on and off thumps/chirps , over a few weeks, that > did not used to be there.   Worse air problem than that. The "baffle" is actually mu-metal plate as the tip of the input jack is about an inch from the speaker line. So another air flow mod for this, a full baffle directing air towards the Zobell, which should also rebalance air inlet to bias towards the main h/s inlet, a bit like the usual MB problem. So perhaps internal HF howl-round was the problem. So add capacitance in the Prea, to downgrade from 20KHz amp, no one has complained before doing this, a bass guitar amp anyway. The relay , now desoldered, was seriously buckled and burnt casing so the contacts were jammed on. As the click/chirp noise had been like that for a couple of months, 3 times a week use, difficult to believe the problem was full on ultrasonic instability driven into 10 W of resitors over the speaker line, all that time. There is a hole behind the front fascia, for a telltale LED to drive off the speaker line. What sort of dropper and cap and zener over the LED+ a rectifier , to come on at elevated amplitude 10KHz and not have the LED fail at full on ultrasonic "full-rail" oscillation

Phil Allison <pallison49@gmail.com>: Nov 21 02:04AM -0800 Nutcase Kook is at it again       > Worse air problem than that. The "baffle" is actually mu-metal plate   ** The Kook see Mu-metal everywhere in his dreams.       > the tip of the input jack is about an inch from the speaker line. > So another air flow mod for this, a full baffle directing air towards > the Zobell,   ** Air cooling for the Zobel - must be a real first.     > So perhaps internal HF howl-round was the problem.     ** No shit Shylock.     > for a couple of months, 3 times a week use, difficult to believe the > problem was full on ultrasonic instability driven into 10 W of resitors > over the speaker line, all that time.     ** Likely only took a minute or so to do the damage, following a short mishap with cables or plugs. The Kook is so pig ignorant there is no explanation he can comprehend or accept.   .... Phil

Jeff Liebermann <jeffl@cruzio.com>: Nov 20 10:19PM -0800 On Sun, 20 Nov 2016 16:54:39 -0000 (UTC), Robert Bannon >> gasoline? How big or how many labels are you removing that the >> process requires gallons of gasoline?   >Thanks for thinking Jeff, and for asking thinking questions.   I won't thank you for questioning my answers.   >This question was always about chemistry.   Also about safety.   >1. I only remove about 1 label a week (or so).   Use the commercial label removing goo. At that rate, a small bottle will last years.   >3. I've tried *all* the chemicals I keep at home.   Since I don't know what chemicals you have at home, that information is useless. However, more interesting would be the type of labels that you're dealing with. You seem to be having far too much trouble for it to be one of the more common types of labels.   I have some permanent labels that have some solvent mixed in with the glue. When attached to plastic or paint, they will literally solvent weld themselves to the plastic or paint, as well as to the plastic backing in the label. When I scrape those off with a razor, I usually find some damage to the underlying paint or plastic.   >9. My hope is that a 1:10 gas:diluent solution will still work.   It won't work very well. Pretend you put a 1 molecule layer of solvent against a glued surface. Each solvent molecule will break one hydrogen bond on one molecule of glue. No problem here. However, you're diluting the solvent 1:10 with perhaps water, which has no effect. So, only one in 11 molecules of glue is disassociated. Of course, other solvent molecules can displace the water, but that take agitation, which is not possible with a thinly glued surface. More simply, the diluted mixture will work 1/10th as well as full strength. <https://en.wikipedia.org/wiki/Solvent>   >10. If it's a 1:10 solution of gas:diluent, it might not stink so bad.   Gasoline is a VOC (volatile organic compound). The stench is produced by simple evaporation. Gasoline volatility is measured as the Reid (absolute) Vapor Pressure is somewhere between 8 and 10 psi. <https://www.epa.gov/gasoline-standards/volatility-regulations-gasoline-and-alcohol-blends> <https://en.wikipedia.org/wiki/Reid_vapor_pressure> It varies with season, type of gasoline, temperature, and whims of the Environmental Protection Agency.   When you mix gasoline with something that has a much lower vapor pressure, such as water which is 0.95 psi at 100F, the vapor pressure remains that of the most volatile component, but with a reduced evaporation rate due a reduction in surface exposure. A bucket of 10:1 gasoline water mix, will have 10 times as many water molecules as gasoline molecules exposed on the surface of the bucket. Therefore, assuming perfect mixing, a really bad assumption as gasoline floats on water, the rate of gasoline evaporation will be 1/11th the rate of a bucket full of 100% gasoline. The room in which you store the bucket of gasoline will have the same amount of smelly gasoline molecules in both cases at equilibrium, but the 10:1 mix might take about 10 times as long to smell up the room.   >I only remove a label about once every week or two.   Use the commercial label remover and be done with the chemistry lessons.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Chris Jones <lugnut808@spam.yahoo.com>: Nov 21 07:04PM +1100 On 19/11/2016 11:05, Robert Bannon wrote:   > What can I 'cut' the gasoline with that will mix with the gas and dilute it > (maybe 10:1 or even maybe 100:1)?   > Any suggestions of common household chemicals that can dilute gasoline?   Don't use gasoline. It still contains enough benzene to mess you up in the long term.   Use biodiesel. It works, and is non-toxic, and cheap. I am talking about trans-esterified cooking oil. There are a lot of websites about how to make it, from KOH, methanol and filthy frier oil, but you can also buy it, usually about the same price as regular diesel. If made (and washed) properly, there is no methanol left in it at the end of the process.   If you doubt its abilities to clean off gunk, here is one example: After a few months it stripped the paint off the inside of my jerry can (and I then had to filter all of the lumps and flakes out so I could use the fuel). It also took the greasy layer off my bathtub better than any household cleaner that I tried. I used it to remove many labels. You can then wash it off easily with ordinary detergent and hot water. It won't melt plastics in the short term (though it might soften epoxy and will swell rubber if you leave it on for weeks). It also smells nice (if you like fried food).

"Michael A. Terrell" <mike.terrell@earthlink.net>: Nov 21 03:16AM -0500 Robert Bannon wrote: > On Sun, 20 Nov 2016 09:53:52 -0500, Michael A. Terrell wrote:   >> A quart bottle of citrus based Goo Gone lasted me over a decade.   > I'll bet you a jar of mayonnaise also lasts a while.   It would last forever, since I don't eat that shit.     > ever again.       > If you knew how utterly *EFFECTIVE* gasoline is for dissolving most goop, > I'd bet you'd never use that goo gone stuff ever again.     If you knew how utterly stupid that your trolling is, you would quit.       > off on contact.   > How long does it take for the googone stuff to melt all the goop off in most > cases?   I use a cotton ball that has a few drops of the solvent on it. I rub it on the label to apply it, then I let it sit for a few minutes. Quite often, the label peels off with no residue. If there is residue, I simply wipe it away with the same cotton ball.   I can even use it to remove price tags from paperback books, without staining the paper. I have removed thousands of inventory labels from SMD component reels, while leaving the OEM labels that they had covered, intact.   It is also good to remove ink from most plastics, without any damage.     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

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