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Clifford Heath <no.spam@please.net>: Feb 17 10:31AM +1100 > I never heard of form taps, but I'll look into them.   They make roll-forming screws also. Google "tri-lobe screw". They're much better and more secure than self-tappers, and you can remove and replace them multiple times without weakening the thread.   Clifford Heath.

amdx <nojunk@knology.net>: Feb 17 10:08AM -0600 On 2/15/2019 4:15 PM, Phil Allison wrote:   > The 465 scope is the culprit, the vertical attenuator needs frequency adjustment.   > With the various probes in 10:1 setting, the trim cap allows you to compensate for the error in the scope.   > .... Phil   Anyone wanting to store this list of TEKtronix probe characteristics should do it now. The link is no longer functional, I went to the Wayback Machine to locate it. > https://web.archive.org/web/20180104162744/http://www.reprise.com/host/tektronix/reference/voltage_probes.asp It has info on about 100 different TEK probes.   Mikek

tubeguy@myshop.com: Feb 17 02:11AM -0600 On Mon, 11 Feb 2019 13:32:07 -0500, Ralph Mowery >temperature are the main killers of the capacitors.   >Any of the good brand capacitors should last longer than most of us will >be around.   Yes, the original question was which caps are BEST, but much of my concern is based on the failed motherboards, which only lasted a year or so.   Knowing the name used on these really bad junk caps would be useful to know too. I'm pretty fussy when I buy caps and some other components, but I do sometimes buy "grab bags" (like on Craigslist) if the price is right, and I know some parts will be usable. But knowing the name used on those conterfeit caps, or any others known to fail is good to know. If the caps are known bad, I am not going to use them for anything other than a breadboard test design, (or not at all).   I'm curious what brand of motherboards were the bad ones too....   It's just good to know things like this. Just like every brand of car seems to have certain common failure or breakdown problems, and knowing what to check and watch for, is helpful.

<dl8fbh@dl8fbh.ampr.org>: Feb 17 04:48PM +0100 > That leads to finding brands which are reliable. And I assume price > tells all. Cheap imports are likely the worst, while high priced US made > ones will last longer.   Electrolytics from Panasonic   Mike

tubeguy@myshop.com: Feb 17 02:11AM -0600 On Mon, 11 Feb 2019 00:43:10 -0600, Fox's Mercantile <jdangus@att.net> wrote:   >which creates a HUGE spike, not related to the turns ratio. >The "return" is through the primary back to the + terminal >on the battery.   This is proof that not all the videos on youtube are accurate. I watched one and the guy insisted that the (-) terminal was the return path for the secondary. Another video said that EITHER primary connector can be used to test a coil for a spark.   It does seem kind of bizarre that the (+) terminal is used for the high voltage return, (knowing that spark plugs complete the circuit by being connected to the engine block, which is connected to the battery GROUND).   I guess this is why I think the circuits are weird. They do not seem to match general electronic knowledge. But they work and have worked for well over a half century, so I am not going to dispute it. Yet, it still seems odd to me.... Especially when I see the high voltage is actually grounding THRU the 12 volt battery.... (without damaging the battery).   Then too, I recall the time I connected a 12v battery charger to a battery connected to a 12VDC electric fencer. It took about 3 seconds for me to see a bright flash inside the battery charger, then smoke. Every diode in that battery charger was instantly destroyed. I still do not understand why the high voltage came thru the "primary" of that fencer, but I now know to never connect a charger to a battery until the fencers is turned off.   And on that same note, I know someone else who connected one of those fencers to the battery in his car for a temporary livestock fence. Not only did he get a nasty shock when he touched his car, but his alternator was destroyed.

Fox's Mercantile <jdangus@att.net>: Feb 17 01:12AM -0600 I'm looking for the manual/schematic for the B&K Model 400 CRT tester.     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Ralph Mowery <rmowery28146@earthlink.net>: Feb 16 06:29PM -0500 Why are switches being rated at different amps ?   I see lots of them on ebay rated for 10 maps at 240 volts and 20 amps at 120 volts.   Looks to me they should have the same amp rating at all voltages. The do not specify any kind of load like something that would draw a larger current at startup with a higher voltage.

Fox's Mercantile <jdangus@att.net>: Feb 16 05:30PM -0600 On 2/16/19 5:29 PM, Ralph Mowery wrote:   > Looks to me they should have the same amp rating at all voltages. The > do not specify any kind of load like something that would draw a larger > current at startup with a higher voltage.   It's because of the arc ratings on switching to off.   -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Feb 16 06:33PM -0500 On 2/16/19 6:29 PM, Ralph Mowery wrote:   > Looks to me they should have the same amp rating at all voltages. The > do not specify any kind of load like something that would draw a larger > current at startup with a higher voltage.     'tain't the turn-on that's the issue, it's the turn-off. That's why fuses rated at 250VAC are also rated at 32VDC.   A friend of a friend was severely injured a couple of weeks ago by an arc flash at a 480V breaker panel. Turning off high-energy circuits is no joke.   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510   http://electrooptical.net http://hobbs-eo.com

Phil Allison <pallison49@gmail.com>: Feb 16 04:38PM -0800 Ralph Mowery wrote:   > Why are switches being rated at different amps ?   > I see lots of them on ebay rated for 10 maps at 240 volts and 20 amps at > 120 volts.   ** The same switch is likely rated at 20 maps for DC switching up to 24V. Above that voltage, contact to contact arcing will become very severe or continuous.     > Looks to me they should have the same amp rating at all voltages.     ** You gotta be kidding.   Inrush surge capacity is another matter, requiring both heavier contacts plus a strong switch off force to pull contacts apart that have become slightly welded.       .... Phil   .... Phil

Ralph Mowery <rmowery28146@earthlink.net>: Feb 16 07:53PM -0500 In article <5badnWXL29d8APXBnZ2dnUU7-dXNnZ2d@supernews.com>, pcdhSpamMeSenseless@electrooptical.net says...   > A friend of a friend was severely injured a couple of weeks ago by an > arc flash at a 480V breaker panel. Turning off high-energy circuits is > no joke.   I have seen the results of a 480 volt 3 phase 'blow up', Fellow at work turned on a breaker that was only a 20 amp rating for a small motor. Not sure what hapened, but it melted down a whole bank of about 30 or 40 cubicals in a load control center. That bank ws fed with around 400 amps from a larger breaker in what we called a substation room. It meleted out the bus bars on that load control center.     When working I dealt with 480 V 3 phase equipment almost daily. Lots of 10 to 100 hp motors and some heaters that were fused at 250 amps.

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Feb 16 07:57PM -0500 On 2/16/19 7:53 PM, Ralph Mowery wrote:   > When working I dealt with 480 V 3 phase equipment almost daily. Lots of > 10 to 100 hp motors and some heaters that were fused at 250 amps.   It's good to wear the Nomex suit and helmet when hacking with that stuff. The FOAF was burned over more than 50% of his body. :(   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510   http://electrooptical.net http://hobbs-eo.com

Andy Burns <usenet@andyburns.uk>: Feb 16 09:34PM >> resistive or capacitive touch at all, it's breaking a grid of infrared >> beams that criss-cross the screen.   > That would be quite expensive in terms of battery use.   Apparently the nook simple touch does have an IR matrix   <https://en.wikipedia.org/wiki/Nook_Simple_Touch>   > And Nooks are > known for very long battery life. My wife will go for over a week, > easily, reading several hours per day.   My kobo will too, it was apparently the last kobo model to use an IR matrix (and I expect kindles last for ages too).

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