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Jon Elson <elson@pico-systems.com>: May 07 04:22PM -0500 philo wrote:     >> Yea, I agree. Should have made that clear in my post.   > At any rate, thought I've seen burned or over-heated connections, I've > never seen one go up in smoke. Another possibility is that the drive developed an internal short (maybe blown power fet in the motor drive) and started drawing huge currents. The connector ended up being the weakest link and burned up.   That is one of the dangers of putting insanely overpowered supplies in PCs. Some people have 700+ W supplies in ordinary desktop systems that typically draw less than 150 W. This is mostly due to sellers making a lot of money over-selling stuff to people who don't know better.   Jon   Jon

"Andy" <N@n.com>: May 08 01:21AM -0400 I have more then once a shorted USB connector is worse:)     -- AL'S COMPUTERS "philo" <philo@privacy.net> wrote in message news:ngk399$mts$1@dont-email.me...

OG <OG@freenewsspamless.net>: May 08 08:26AM -0700 Upon further examination it looks like the connector may have wiggled loose. Why, because the gold connector pads on the HDD were melted off only near the edge of the connector. Little damage to the PWB of the HDD. I see no damage to the gold from that damaged area into the HDD.   A short occurred between the 12v Yellow and GND Black power feed. The connector evaporated there (ash and chunks all over) and the wires evaporated back from where the connector was by over an inch. Yes, over an inch of yellow and black (adjacent) wire evaporated. Must have been exciting to see the arc.   So probably the arc started, the connector evaporated and came off the HDD, the arc continued and ate the wires until the PS gave its all then had enough.   So the smoke was a combination of gold, connector plastic, copper PWB trace, copper wire, vinyl wire covering and whatever else was in the mix. Thankfully I did not get to breath much since the whole house fan and computer room fan were immediately turned on and evacuated the "computer" room quickly.   Got a new PS and HDD ready to install. Will take baby steps putting it all together. The new EVGA PS is much higher efficiency than the last. The new HDD is a WD "Black".     --- news://freenews.netfront.net/ - complaints: news@netfront.net ---

Jeff Liebermann <jeffl@cruzio.com>: May 07 10:05AM -0700 On Sat, 7 May 2016 00:02:40 -0700 (PDT), Phil Allison >> Simple setup: >> <http://802.11junk.com/jeffl/Electrolytic-cap-test/test-setup.jpg>   >** You went to lot of trouble to see the obvious.   Cap-B was one that had failed with high ESR. There was plenty of data and anecdotal evidence on how a normal capacitor would act. I wanted to see how a defective capacitor acted. I also wanted to see how the ESR meter functioned with small value and size (0.22uF 50v) caps, which was Cap-D. The change in ESR with temp was far less radical than the others. <http://802.11junk.com/jeffl/Electrolytic-cap-test/Cap-D.jpg> I also found as similar problem with high capacitance values (1800uF 6.3v) which was Cap-A, where the lower limit capability of the ESR meter (about 0.03 ohms) also caused the graph to flat line. I didn't mention this in your previous discussion on the matter, but I was trying to determine if it made sense to use a fixed 100KHz sine wave signal, and whether higher or lower frequencies might help test a wider range of capacitance values. I have a pathological aversion to accepting the obvious, and will take the time to test the obvious, which invariably produce surprises.   >All I did was try a few 450V electros, heat them with a hot air >gun until they were darn uncomfortable to hold and note that in >every case the ESR reading had plumeted by 5 to 10 times.   I wasn't interested in high voltage electrolytics. There are usually two of those in a typical ATX power supply. They never seem to fail. It's the low voltage electrolytics, that inhabit the output filters and regulator circuitry that fail and were of interest to me. I probably could have done it using your method, but I thought a hot water bath was more interesting and accurate.     >** I use the same one as in your pics - the Bob Parker design. He >lives not far from me and we have conversed about that an many >other electronics matters.   Yep. It's an impressive instrument, quite accurate, but a little tricky to build (Dick Smith kit version). Methinks the later "blue" variety might be better. <http://anatekinstruments.com/products/fully-assembled-anatek-blue-esr-meter-besr>   >Have you tried your meter to test the ESR of cells ? >Easy to tell if a Lithium memory cell is good or not - also good on >NiCds, NiMH and alkalines.   One of the common modifications to the original ESR meter is to add two back to back power diodes across the input to protect the meter from residual voltages. The problem with doing that is that the diodes short out the battery. Since I expected to be testing far more capacitors than batteries, this made sense.   I also have a Capacitor Wizard ESR meter that I picked up cheap at a flea market: <http://anatekinstruments.com/products/capacitor-wizard-esr-tester-cap1b> <http://anatekinstruments.com/products/capacitor-wizard-esr-tester-with-capsvr-module-cap1b-capsvr> The CapSRV model has the same diode protection circuit making it useless for battery measurements. There's nothing particularly wonderful about this meter except that it's very fast and convenient. One problem is that I seem to have misplaced it and can't seem to find it. Argh.   I also have a Peak Atlas ESR70 "purple" ESR meter. <http://www.peakelec.co.uk/acatalog/jz_esr70.html> It has a built in discharge resistor to help deal with charged capacitors and therefore is useless for testing battery ESR.   Bottom line is that I don't use any of my ESR meters to test batteries. I probably should build or buy something specifically for the purpose to see what I'm missing. All of my battery testing involve small rechargeable batteries, a discharge tester, and computized graphs such as: <http://802.11junk.com/jeffl/LiPo/Ultrafire%2018650%20test.jpg> <http://802.11junk.com/jeffl/LiPo/Ultrafire%20LiPo%203000%20ma-hr%2018650%20test.jpg> However, I'm getting into larger cells and sealed packs, where an ESR tester is quicker and probably more useful.   >Also reads low value resistors, even if there is an inductor or >transformer winding across one.   Yep. I've used that to determine the value of a charred resistor. Usually, it's a wire wound resistor with a break somewhere along the winding. I measure from one lead to the middle of the winding. One end is usually open, while the other end reads half the resistor value. However, testing electrolytics is my main use for an ESR meter.     -- 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

Fred McKenzie <fmmck@aol.com>: May 07 02:02PM -0400 In article <MPG.3196c6b2ce898bd39896a0@news.east.earthlink.net>,   > I would guess the .068K would be a .068 UF at 250 volts. They seldom go > bag.   I agree. The K probably indicates 10% tolerance.   Regardless, it is either .068 Microfarads or 68K (68,000) Picofarads, which is the same thing!   Fred

Dimitrij Klingbeil <nospam@no-address.com>: May 08 12:35AM +0200 > weak electrolytic , so concentrate there.   > If there's only a few electrolytics, change them all with good > quality (I like Panasonic) caps and they'll probably run.   Good advice. But there is one more small-ish pitfall for the unwary. If a power supply refuses to start when cold, it's usually an electrolytic cap. But in many cases it's not one of the big caps but the small one that is located in the start-up / auxiliary section.   Mains power supplies usually have an auxiliary section that is used to power the internal needs of the primary side switching circuitry. This section is powered by a small auxiliary winding on the transformer in steady-state. But because it needs to start up first, and because at first the main transformer is not yet operating, it is precharged with a high value resistor (or sometimes a string of 2 or 3 resistors in series) directly from the rectified mains. There is a small (47 uF or similar, 25 to 35 V typically) electrolytic. At first it gets precharged through the resistor up to the point where the controller chip can start up. Once the controller starts, it would rapidly drain the small cap, so the main switching circuitry has to come on line fast in order to top up the the auxiliary supply cap and keep it from discharging.   Now this small cap only provides little reserve. It's usually sized very spartanically and it lasts for just one try and only if the start-up timing of the switching circuitry is not delayed for any reason. If it drains before the switcher can fully start, the switcher will stop and wait for another retry at a later time.   Often this small cap is considered "non-critical" and carelessly placed by the power supply designer into whatever corner had whatever little free space. This may happen to literally be a "corner" of a heatsink!   When this cap dries out either from overheating of just being selected from the cheapest manufacturer, it will rise in ESR and thus no longer provide the peak current that the controller needs in order to start. This either delays the start to the point where the cap is drained or causes it to outright abort prematurely because the auxiliary supply rail tanks right at the first few switching cycles.   When warmer it has lower resistance, thus it can provide higher peak currents and have better chances of starting the supply successfully. Also if the supply is working continuously for many years and never switched off, the condition of this capacitor is of no consequence during operation. Even if somebody just cut it out of a working power supply, there are usually some small ceramics on the rail and the auxiliary transformer winding will keep them topped up, so that the supply would quite likely keep on working. But if the supply ever gets switched off, even for a very short time, it will never start up again.   If you see this type of behavior, find and replace the cap in the auxiliary section. You can normally identify it as being physically small, a low voltage type (from 25 to 50 V) and being connected to a sizeable precharge resistor that gets supplied from the high voltage DC rail.   If you don't have an exact replacement, it's normally OK to use the next higher capacitance as long as the voltage rating fits. If you find that yours sits in the corner of a heatsink, use a low ESR high temperature rated replacement (no matter what the original has been) and some reasonable reserve capacitance-wise won't hurt either.   Dimitrij

Phil Allison <pallison49@gmail.com>: May 07 06:18PM -0700 Jeff Liebermann wrote: Phil Allison   > Cap-B was one that had failed with high ESR. There was plenty of data > and anecdotal evidence on how a normal capacitor would act. I wanted > to see how a defective capacitor acted.   ** Well, that depends how *defective* it actually is !!!   An electro that has lost nearly all of its fluid and reads off-scale on Bob Parker's meter is not likely to come good with a bit of heat.     > ESR meter functioned with small value and size (0.22uF 50v) caps, > which was Cap-D. The change in ESR with temp was far less radical > than the others.   ** Even a 0.22uF film cap reads 7 ohms on the Bob parker meter - IOW the impedance of the thing at 100kHz. Bob's meter does not read actual ESR values, rather it reads impedance vales at 100kHz.   This *fact* is pointed out in the instructions and the lowest value electro you can reliably test is about 1uF - as shown on the front panel table.   A man has gotta know the limitations of his ESR meter. ------------------------------------------------------     > >gun until they were darn uncomfortable to hold and note that in > >every case the ESR reading had plumeted by 5 to 10 times.   > I wasn't interested in high voltage electrolytics.   ** They have higher ESR values than low voltage caps, so there is plenty of room for ESR readings to come down without approaching the low reading limit of Bob's meter.   I used a value of 47uF, so its reactance at 100kHz was negligible.   Pays to think ahead, you know.     .... Phil

Ralph Mowery <rmowery28146@earthlink.net>: May 07 11:47PM -0400 In article <0001HW.1CDE42940005391D11ECB93CF@news.eternal- september.org>, not@home.cow says... > culprit!? does not help the customer (or yourself, if it?s you). The unit > will be back on your bench very soon if you don?t replace all electros now, > if you find one or more below spec.     Unless the capacitors are very expensive, it is best to just replace them all even if only one or two is showing up to be the problem.   When working a factory repair man came in to repair a 300 HP electric motor varitable speed drive. This was a 3 phase AC input. He determined 2 out of 3 large diodes were bad. I asked him to replace the 3 rd one and he said those were about $ 100 each. I said so what, the equipment beind down was costing several thousand dollars an hour and another $ 20,000 to start it up and shut it down. At that ratio of dollars to production I thought it would be a good idea to replace it even if it was good. I am sure it would have started, and may have ran from then on, but why take a chance it would crap out a week or even a year later.

Jeff Liebermann <jeffl@cruzio.com>: May 07 08:50PM -0700 On Sat, 7 May 2016 18:18:16 -0700 (PDT), Phil Allison >> and anecdotal evidence on how a normal capacitor would act. I wanted >> to see how a defective capacitor acted.   > ** Well, that depends how *defective* it actually is !!!   Well, cap-B was labeled 2200uF 10v and was bulging at the top. Room temp ESR was measured at about 2.3 ohms: <http://802.11junk.com/jeffl/Electrolytic-cap-test/Cap-B.jpg> and should have been about 0.1 ohms according to the latest chart for my ESR meter: <http://802.11junk.com/jeffl/crud/ESR.txt> It's the 2nd from the left in: <http://802.11junk.com/jeffl/Electrolytic-cap-test/caps.jpg> and shows no signs of leakage except for the bulging top.   > An electro that has lost nearly all of its fluid and reads > off-scale on Bob Parker's meter is not likely to come good > with a bit of heat.   True. However at 100C, the ESR dropped to 0.25ohms which is not perfect but would probably be adequate for most purposes. <http://802.11junk.com/jeffl/Electrolytic-cap-test/Cap-B.jpg>     >** Even a 0.22uF film cap reads 7 ohms on the Bob parker meter - >IOW the impedance of the thing at 100kHz. Bob's meter does not >read actual ESR values, rather it reads impedance vales at 100kHz.   Right. The impedance is the vector sum of the resistive (ESR) component and the capacitive reactance of the capacitor. At 100KHz: Xc = 1 / (2*Pi*MHz*uF) = 1 / 2*Pi * 0.1 * 0.22 = 7.23 ohms If the ESR were the typical less than 1 ohm, the bulk of what the meter is reading is from the capacitive reactance.   The meter was reading exactly 7.00 ohms, I can get a rough idea of the resistive ESR from: R = sqrt(Xc^2 - Z^2) = sqrt(7.2^2 - 7.0^2) = sqrt(52.3-49) = 1.8 ohms   However, let's pretend that this capacitor was defective and it exhibited a higher ESR, such as 6 ohms. What would the ESR meter read? Same formula: Z = sqrt(R^2 + Xc^2) = sqrt(6.0^2) + 7.2^2) = sqrt(36+52.3) = 9.4 ohms You would be able to see the difference between a good 7.0 ohm reading and a bad 9.4 ohm reading, but only if you did the calculations in advance. I once played with an HP/Agilent LRC meter that did all this automatically. it would be nice if the next generation of ESR meters could also do that.   Raising the frequency to 1MHz would reduce the capacitive reactance to 0.723 ohms, which would produce something closer to the real ESR. However, the ESR changes with frequency, so accuracy will suffer.   >value electro you can reliably test is about 1uF - as shown on >the front panel table.   >A man has gotta know the limitations of his ESR meter.   I just hate reading the instructions. However, the 1uF lower limit is printed on the front of almost every ESR meter. My Capacitor Wizard has it boldly displayed on the front panel. <http://www.howardelectronics.com/images/thumbnails/1138/1138/detailed/1/CAP-WIZARD.jpg?t=1440164290>   >the low reading limit of Bob's meter.   >I used a value of 47uF, so its reactance at 100kHz was negligible.   >Pays to think ahead, you know.   Yeah, but I think you missed my point. I don't do tube amplifiers and therefore do not run into too many high voltage capacitors. The one's I see most of are low voltage and high capacitance electrolytics as found on PC motherboards, ATX power supplies, LCD monitors, wall warts, and various consumer electronic devices.   Incidentally, speaking of tubes (valves), you might be amused by this: <https://www.kickstarter.com/projects/1815752970/hybrid-tube-amp-for-the-raspberry-pi>     -- 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

Phil Allison <pallison49@gmail.com>: May 07 11:15PM -0700 Jeff Liebermann wrote: > >IOW the impedance of the thing at 100kHz. Bob's meter does not > >read actual ESR values, rather it reads impedance vales at 100kHz.   > Right.   ** Then you should not have posted what you just did. The actual change in ESR of a 0.22uF 50V electro was not readable on a Bob Parker meter.   What is really happening is the electrolyte becomes more conductive at higher temps, many times more in the range from 20C to 100C. It is the resistance of this fluid that dominates the ESR value.   > >A man has gotta know the limitations of his ESR meter.   > I just hate reading the instructions.     ** Right - you take zero notice of anything others tell you.           > >I used a value of 47uF, so its reactance at 100kHz was negligible.   > >Pays to think ahead, you know.   > Yeah, but I think you missed my point.   ** No I didn't. You missed mine, as usual.     .... Phil

Tekkie® <Tekkie@comcast.net>: May 07 03:14PM -0400 Danny DiAmico posted for all of us...     > while I'm not sure what to trust in that board.   > So, I *would* have gone for the $25 board if I had more information, > but I didn't have enough to trust Ebay.   Everybody has their comfort level. It's the crap shoot of life.   Isn't it time to collect money off your sister? Is she the one that broke it? <g> Map the laundromats?   -- Tekkie

Danny DiAmico <dannydiamico@yahoo.com>: May 08 12:10AM On Sat, 07 May 2016 15:14:48 -0400, Tekkie® wrote:   > Everybody has their comfort level. It's the crap shoot of life.   > Isn't it time to collect money off your sister? Is she the one that > broke it? <g> Map the laundromats?   I think the multiple power surges during the recent rain is what fried the MMU board.   I haven't heard anything from the rebuilders yet, but I'll let you know what happens when I know.

N_Cook <diverse@tcp.co.uk>: May 07 08:12PM +0100 On 07/05/2016 13:21, Jeroni Paul wrote: >> The neons run at 24 deg C over ambient, so perhaps 5 or 6 would be >> better if more than a temporary fudge.   > I have been looking for a practical/cheap solution for the same problem on a DELL 1707FPt computer display. It has four backlight tubes two at the top and two at the bottom. One of them was cracked and very darkened inside, the rest were fine. Problem is the inverter is not happy without a load on that output, runs for one second and shuts down. I tried three 3W resistors in series adding 120K and it works fine, yet the resistors get quite hot. The missing tube is barely noticeable, it just causes the top 1/3 of the srceen to be slightly darker but goes mostly unnoticed. I would be happy to make it work with three tubes, installing the resistors permanently is one solution but I wondered if the inverter could be modified somehow to disable or ignore that output. The inverter uses a transformer for each pair of tubes so not sure if there is anything that can be done.   This TV was running perfectly happily with 6 neons in series without any droppers, replacing the failed tube for loading purposes, for 3 hours as a try out of whether it was possible

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