sci.electronics.repair@googlegroups.com

Google Groups

Dusty <Dusty@DustyDustyDusty.COM>: Sep 25 09:25AM -0700 Any PC I plug it into pops up a message saying the driver is now installed BUT it does not show anything in Windows Explorer. This happens on a Win XP Pro laptop, a Lenovo laptop and a Win 7 Pro desktop.   The light on the pen drive blinks one long blink then a short one or two blinks.   Any chance of recovery ?   Any app to explore it ?   It is all backed up but it will take over night to fill a new pen drive so getting this one going would be better.   What brand is the most reliable pen drive ? Need 32 G.

mike <ham789@netzero.net>: Sep 24 05:52PM -0700 >> be 10V at MUCH higher current ratio. You will have to live >> with some amount of nonlinearity.   > In fact you could re-zero the meter so it reads 10v spot on. Add an extra mark for where it points when unpowered so you can see if it ever decalibrates.   Yes, you can , but it's still nonlinear. It's a matter of how much nonlinearity you can tolerate. It's my assertion that the measured quantity is so crude that you don't need to worry much about anything. Just learn what it reads and calibrate your expectations to match.   >> You could stack an AA-cell or two on top of your battery system >> and alleviate that problem.   > yuck. 2 resistors beats 2 cells any day. Can't argue with that assertion, but, if you can provide a circuit that is precisely linear and accurate over the WHOLE range using two resistors, I'd like to see it. I'm betting it's more than two resistors.   >> I maintain that a digital voltmeter is the best option. >> They're dirt cheap on EBAY.   > but noncompliant with the basic spec Yep, that's a problem with any customer expectation. I try to adjust expectations to meet the ACTUAL requirements before delving into complex solutions to implement a nonsense requirement. Yes, the customer is always right. My job is to alert him to the consequences of his demands.   Another non-complient solution is to use the two resistors and a zener to make a 9V-15V meter and hope that most of the nonlinearity of the two resistor solution happens in the 9-10V range. That way, the characteristics of the zener knee are important over a 5:1 current range instead of an infinite ratio. I'm far too lazy to do the math on how nonlinear it will be.   There's also an elephant in the room. Unless you start with a meter that happens to have scale markings ranging from 10 to 15, you're gonna need a new scale no matter what you do with the electronics. If you're not gonna do that, might as well just mark calibrations on the face with a sharpie. Makes no sense to go to great lengths in one part of the project only to create something that still doesn't do what you want.

tabbypurr@gmail.com: Sep 24 06:05PM -0700 On Monday, 25 September 2017 01:53:43 UTC+1, mike wrote: > range using > two resistors, I'd like to see it. I'm betting it's more than two > resistors.   What I meant is divide the input to your opamp so it's away from the rails and you don't need any rail boosting.     NT

T i m <news@spaced.me.uk>: Sep 25 04:43AM +0100 >It's my assertion that the measured quantity is so crude that you don't >need to worry much about anything. Just learn what it reads and calibrate >your expectations to match.   (I've been a bit preoccupied elsewhere but still following the thread with interest and will reply individually when I get the chance)   That was part I had already considered in that: The meter is fairly small. The meter is glued shut. The meter is only marked in whole volts.   So, as you say, afa this experiment is concerned it was a cheap toe-dipping into the concept of meter range enhancement, partly because I think analogue display still have some merit and partly for the S&G's. ;-)   <snip>   >I try to adjust expectations to meet the ACTUAL requirements >before delving into complex solutions to implement a nonsense >requirement.   In this case the actual requirements were fairly simplistic as it was an experiment. A feasibility study if you will. As you say, a DMM can be bought for next to nothing (and I have several and one I'm already using) but that wasn't the (entire) point.   >Yes, the customer is always right. My job is to alert him >to the consequences of his demands.   ;-)     >and a zener >to make a 9V-15V meter and hope that most of the nonlinearity >of the two resistor solution happens in the 9-10V range.   With a very small buck converter you could get a higher voltage supply to ensure a voltage reference of some sort had sufficient overhead to work correctly when close to the 10V threshold?   >That way, the characteristics of the zener knee are important >over a 5:1 current range instead of an infinite ratio.   ITRW, as long as it's starting to work reasonably by 10.5V it shouldn't really be an issue.   >I'm far too lazy to do the math on how nonlinear it will be.   I do like the idea of printing my own scale and if this basic one works, I might go for a bigger / better meter that I can open etc. >Unless you start with a meter that happens to have scale >markings ranging from 10 to 15, you're gonna need a new scale >no matter what you do with the electronics.   Unless it's already marked 0, 1, 2, 3, 4 and 5 'Volts' and you know just have to add 10 to all of them. I would imaging the needle pointing up the middle to 12.x would be a sufficient comforter. ;-)   >If you're not gonna >do that, might as well just mark calibrations on the face with a >sharpie.   Only if I can get the thing open and it wouldn't be worth damaging it to try.   >Makes no sense to go to great lengths in one part of the project >only to create something that still doesn't do what you want.   My only hope is that it works 'better' than a similarly sized and accuracy meter that is marked 0 to 15 and using it over a tiny proportion of the range.   As has been suggested, if you aren't happy to try to KISS then you are then going to be worrying about thermal stability and scale linearity and I'd like to leave that for the Mk2. ;-)   Cheers, T i m

mike <ham789@netzero.net>: Sep 24 04:05AM -0700 On 9/22/2017 1:29 AM, T i m wrote: > the question. I left it open to the reader to ask any supplementary > questions as they felt relevant. ;-)   > Cheers, T i m   Metrology is an interesting topic.   When someone asks me how to measure something, my first thought is, "exactly how will the answer to your question improve YOUR life tomorrow?" Sometimes I actually say it. The "jolt" to their thought process forces them to express what they're trying to accomplish...or admit to themselves that they have no idea. I find that almost all questions end up in the "won't affect them at all" category and I can dispense with trying to teach them something they'll never use. If the answer won't change the future, don't bother with the question.   It's similar to pointless social interaction. People you don't know ask questions, like "how are you?" They think they know what you'll say. Respond with something like, "I have this rash on my dick and think I need to find a different street corner... got any ideas?" to see how much they really care about how you are. ;-) But I digress...   If I had an electric boat, the ability to measure voltage to six decimal places would not be my priority. What I want to know is, "can I get back to the dock?" You can do that more accurately with a sharpie and nonlinear meter than you can react to a change in wind direction.   The river current and wind and the shape of the curve of distance covered vs velocity and temperature would be far more important variables to me. Amp hours consumed would be important.   Battery voltage that would be strongly impacted by whether I'm going up or down stream at what net velocity is a poor substitute.   An integrating current meter, a water speed speedometer and a GPS would much more interesting. If you knew the water flow direction and speed, you probably wouldn't have to measure anything else other than what you can get from the GPS. Drifting downstream for a minute would give you those two numbers.   But, since you're dead set on measuring voltage... The basic problem is that the voltage you want to measure is the biggest voltage you have to power your circuit. That's why I split my original post into the concept (battery) and the implementation (zener). A series zener needs to draw ZERO current at 10V and still be 10V at MUCH higher current ratio. You will have to live with some amount of nonlinearity.   You could stack an AA-cell or two on top of your battery system and alleviate that problem.   I maintain that a digital voltmeter is the best option. They're dirt cheap on EBAY.   All the above is based on an extreme extrapolation of very limited information. That's why the system spec is so important.

T i m <news@spaced.me.uk>: Sep 25 09:58AM +0100 On Fri, 22 Sep 2017 14:13:13 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:   >arbitrary zener (I'd use a TL431 as a 2.5V reference, they're convenient >and accurate) and a trimmer acting as voltage divider, it just remains >to make a range-setting resistor in series with the meter.   Hmm, that's crafty. ;-)   I'm trying to picture how the voltage rise would still be linear but I think I can see how it would be.   The -ve of the meter is held at some voltage threshold low enough to ensude a low change in difference between the voltage measured and the ground. A variable (to start with at least) resistor set as a pd then sets the upper voltage to give FSD at 15V.   >The important thing, is to doodle up a really nifty scale for your meter >that indicates 10V to 15V, with clear markings, along the pointer's arc, >maybe with a bunch of subdivision marks.   Yeah, that sounds like a interesting project for a Mk2 meter. ;-)   >took >a plotter and a bit of custom software to draw the arcs and labels,   I saw the link to some free software for doing such but not had chance to try it yet.   >then some fiddling with the faceplate of the meter to >affix it (warning: you need to worry about laser-print ink, paper, glue compatibility).   Ok. ;-)   Cheers, T i m

mike <ham789@netzero.net>: Sep 25 02:00AM -0700 >> two resistors, I'd like to see it. I'm betting it's more than two >> resistors.   > What I meant is divide the input to your opamp   Thereyougo...opamp is a lot more complex than two resistors...or a couple of AA cells.   so it's away from the rails and you don't need any rail boosting.

T i m <news@spaced.me.uk>: Sep 25 10:21AM +0100 On Fri, 22 Sep 2017 10:53:54 -0500, "Dave M" <dgminala@mediacombb.net> wrote:   >as low power a zener that you can find, such as 400mW or lower. >The 1N4104 is a 10V, 250mW zener, with a test current of 1uA, and a max >current of 25ma, well within your requirements. In stock at Mouser.com.   Cheers, Dave, I'll have a look.   As has been mentioned elsewhere, if we used a lower voltage zener (and as high a tolerance as can be found in the right spec and the right price *because*) to set the voltage on the -Ve leg of the meter and then tweak the voltage up via resistors (variable initially) to give a FSD at 15V then that should be sufficient?   I can't help feeling I've missed something with that solution though, like the linearity ... ? ;-(   Cheers, T i m

tabbypurr@gmail.com: Sep 25 03:41AM -0700 On Monday, 25 September 2017 04:43:06 UTC+1, T i m wrote:   > That was part I had already considered in that: > The meter is fairly small. The meter is glued shut. The meter is only > marked in whole volts.   If it's not an accurate meter just add a zener, job done.     NT

tabbypurr@gmail.com: Sep 25 03:44AM -0700 On Monday, 25 September 2017 10:01:42 UTC+1, mike wrote:   > > What I meant is divide the input to your opamp   > Thereyougo...opamp is a lot more complex than two resistors...or a couple > of AA cells.   I'm pretty sure we all know that, and what the options are, and what the pros & cons are. And that adding AA cells rather than 2 resistors on the input is not an option with any upside.     NT

T i m <news@spaced.me.uk>: Sep 25 12:37PM +0100 On Mon, 25 Sep 2017 03:41:49 -0700 (PDT), tabbypurr@gmail.com wrote:   <snip>   >> The meter is fairly small. The meter is glued shut. The meter is only >> marked in whole volts.   >If it's not an accurate meter just add a zener, job done.   Well, I'm not sure if it's electro mechanically any more or less 'accurate' than any similar style meters and being smaller with a shorter / lighter needle it's possible it could be better than some ... but regarding the potential display markings and readability, you may well be right. ;-)   Cheers, T i m

tabbypurr@gmail.com: Sep 25 07:13AM -0700 On Monday, 25 September 2017 12:37:05 UTC+1, T i m wrote: > ... but regarding the potential display markings and readability, you > may well be right. ;-)   > Cheers, T i m   If it's only marked in whole volts, reading it with accuracy won't happen, so it won't be especially accurate.     NT

"pfjw@aol.com" <pfjw@aol.com>: Sep 25 07:53AM -0700 > If it's only marked in whole volts, reading it with accuracy won't happen, so it won't be especially accurate.   How so? I suggest that you are mistaking "accuracy" for "precision". They are not even a little bit the same thing nor follow necessarily one from another.   A gauge or meter that reads (is marked) in whole numbers but is dead-on is far more accurate than a gauge or meter marked in thousandths, but is always two units off. Although the latter meter is extremely precise.   I have a metered Iso-Variac that reads in volts measured in tens, and amps measured in tenths on a 0 -1 or 0 - 4 scale. But they are 4" meters so that even very slight needle movements are visible. The human brain is pretty good at interpolation.   Peter Wieck Melrose Park, PA

Stephen Wolstenholme <steve@easynn.com>: Sep 24 04:04PM +0100 On Sun, 24 Sep 2017 07:32:38 -0700 (PDT), Amanda Ripanykhazov   >Is there some overwhelming technical problem with replacing a Priv screen please?   >All screen replacement services are MASSIVELY expensive (the LCD alone seems to cost $180) and places like ebay are full of Privs on which the owners seemingly cant replace their cracked screens?   >Curiously, ebay sales are rife with digitiser offers, - where the digitiser cant actually be replaced because it cant practically be separated from the LCD! What is going on?? On every other cellphone the repair cost nose-dives when the phone stops being current!   Watch https://www.youtube.com/watch?v=lRj_F7b4JvE   It looks a bit tricky with my jumbo fingers!   -- http://www.npsnn.com

Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au>: Sep 25 08:34AM +1000 On 24/09/2017 12:59 PM, micky wrote:   > I"m looking at a panel-mount extension cord for a car radio with USB and > 3.5mm inputs, and someone asks "could i use this to connect a usb > headset to the 3.5mm headphone jack on my tv?"   **No.   > it's USB! It's uses some sort of fancy USB signal, like all the other > USB devices do. It doesn't have L+, R+ and ground, like earphones with > round plugs on the end have. OR does it?   **No, it doesn't. USB (Universal Serial Bus) is a digital connection system. Any audio signal present is in a digital form and must be converted to analogue, before it can be heard.   > get their power from the USB, and they work very well. If I'm wrong > above, does the power piggyback on one of the 3 wires or does it use the > fourth wire?   **Part of the USB convention is that a small amount of DC power can be transferred to devices that require it.     -- Trevor Wilson www.rageaudio.com.au

"~misfit~" <shaun.at.pukekohe@gmail.com>: Sep 25 02:15AM +1300 Once upon a time on usenet micky wrote: > they get their power from the USB, and they work very well. If I'm > wrong above, does the power piggyback on one of the 3 wires or does > it use the fourth wire?   Maybe the 5th - the shield ground? -- Shaun.   "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders)

"~misfit~" <shaun.at.pukekohe@gmail.com>: Sep 25 02:11AM +1300 Once upon a time on usenet Percival P. Cassidy wrote: > will depend on how densely it's packed -- could be as little as 5 oz. > rather than the 8 oz. that the "pint's a pound the world around" > formula indicates.   At school I was taught 'A pint of water weighs a pound-and-a-quarter'. Then again that was in England. -- Shaun.   "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders)

Bruce Esquibel <bje@ripco.com>: Sep 24 10:29AM > Do any of you know anything good or bad about Grom audio? Do any of you > know a competitor you would recommend (instead?)?   No comment on them but a general 2-cent comment.   Keep in mind that most of these "adapters" need power, usually by a rechargeable battery built into them and that is the major pain in the ass.   I had a 97 Lincoln that had a non-replaceable radio (amps and other parts of it were scattered all over the car), it had a cassette player and 10 disc cd changer but since you can get like 1400 mp3's on a cheap 16GB ipod, I wanted to use one of those.   They probably are still made (maybe) but there was a cassette to bluetooth adapter and it really worked well, provided it was charged up. Battery life was only 4-6 hours and it really sucked when 15 minutes into a 2 hour drive it starts beeping at you to charge it up. Back to the radio.   I'd really recommend if whatever you are looking at isn't wired into the car, forget it.   My overall recommendation is screw all these adapters and replace the radio.   I don't know what kind of car or truck you have but you should be able to find from Crutchfield, a radio, wiring harness that supports the steering wheel controls and if needed, the adapter plate (bezel) for $150 or less.   Most of those under $100 radios they sell have at least 1 usb port (the dual ones are front/back, the back if you want to run a cable somewhere), usually bluetooth and have a aux input.   My point is, it's a little more expensive than it seems you are planning on, will take at least an afternoon of work to install but once it's done, you just don't have to worry about anything. Provided you remember to bring the phone/ipod or usb stick with you, it just works.   I put up with that cassette adapter for 4-5 years and although it was worth the $35 or so it just wasn't dependable. I replaced the car earlier this year with another used Lincoln, but the at least the radio was more standard. I wanted to try that apple carplay and although it ran almost $500 for everything, I'd never get another car without it.   I'm pushing 60 and the last car radio I installed was back when dashboards were still made of steel and although it took me 3 attempts over 3 days to get everything to work right (who would of thunk to attach the tripwire for the amps to the power antenna lead from the radio), I'd do it again in a heartbeat.   I stuffed all the wiring via the shift tunnel into the center console thing and don't have any wires or plugs exposed. If you go on a short trip and don't plug the phone/ipod in, the radio does a search for a bluetooth connection automatically and off ya go. Can still switch tracks and control volume from the steering wheel and make hands-free phone calls.   All those adapters have their place but for long term enjoyment, replace the radio.   -bruce bje@ripco.com

John-Del <ohger1s@gmail.com>: Sep 24 11:32AM -0700 On Sunday, September 24, 2017 at 5:34:07 AM UTC-4, mike wrote: > Note that the voltage at the instant you apply the load won't be available > unless you use a scope, or some otherwise accurate sampling to measure it.   > Great in theory, but not nearly so simple in practice.   If you're applying a load suitable enough to cause a constant drift of voltage or the OC voltage doesn't return to pre test state, the load is too high for the battery in question or the battery is shot. Old School battery testers used to use a switch to select which resistor to load down the battery in question, AA, AAA, C, etc., while displaying the battery voltage on the meter. The only time I saw the meter drift downward was if selecting a D battery test for a AAA for instance.

tabbypurr@gmail.com: Sep 24 12:29PM -0700 On Sunday, 24 September 2017 19:32:47 UTC+1, John-Del wrote: > > unless you use a scope, or some otherwise accurate sampling to measure it.   > > Great in theory, but not nearly so simple in practice.   > If you're applying a load suitable enough to cause a constant drift of voltage or the OC voltage doesn't return to pre test state, the load is too high for the battery in question or the battery is shot. Old School battery testers used to use a switch to select which resistor to load down the battery in question, AA, AAA, C, etc., while displaying the battery voltage on the meter. The only time I saw the meter drift downward was if selecting a D battery test for a AAA for instance.   If your battery voltage is drifting down, its ESR is drifting up. If you want to know what state it's in after the test you'd use the last voltage reading. But there's no point, if it's dropping noticeably either it's had its day or the test load is too high.     NT

mike <ham789@netzero.net>: Sep 24 06:02PM -0700 >> If you're applying a load suitable enough to cause a constant drift of voltage or the OC voltage doesn't return to pre test state, the load is too high for the battery in question or the battery is shot. Old School battery testers used to use a switch to select which resistor to load down the battery in question, AA, AAA, C, etc., while displaying the battery voltage on the meter. The only time I saw the meter drift downward was if selecting a D battery test for a AAA for instance.   > If your battery voltage is drifting down, its ESR is drifting up. If you want to know what state it's in after the test you'd use the last voltage reading. But there's no point, if it's dropping noticeably either it's had its day or the test load is too high.   > NT   Do the math. How much current do you apply? How much voltage represents 0.1 ohm of ESR? Compare that to the change of voltage over a second when you apply that current to a brand new battery. The battery model is more than a resistor in series with a fixed voltage source. Maybe someone here can supply the actual model of a battery that represents the voltage over time for a given current as a function of recent history of the battery load.   The only way I got usable ESR results for matching cells was to apply a square wave switching from one non-zero load to a different non-zero load and measuring the amplitude of the square wave...always using the same frequency of square wave. The devil is in the details.

tabbypurr@gmail.com: Sep 24 06:09PM -0700 On Monday, 25 September 2017 02:03:00 UTC+1, mike wrote: > the amplitude of the square wave...always using the same frequency > of square wave. > The devil is in the details.   that's all good if you want precision. In a lot of cases it's enough to see that oc voltage is down or it's drooping under load a good bit so it's shot.     NT

KnowName <KnowName@NoPlace.com>: Sep 24 05:13PM -0700 Purchased a refurbished Lenovo T500. It is in great like new shape with Win XP Pro installed. Just what I need.   BUT ... the keyboard is not installed properly.   The left-hand side of the keyboard depresses with a key press. The right-hand side is fine.   So maybe some thing is missing to keep the keyboard from depressing.   I will be using this laptop extensively so i do not want it to have a keyboard problem related to this flexing.   How to get the keyboard out ? What to use to bolster the keyboard on the left side. ?   TIA

Jeff Liebermann <jeffl@cruzio.com>: Sep 24 06:04PM -0700 On Sun, 24 Sep 2017 17:13:04 -0700, KnowName <KnowName@NoPlace.com> wrote:   >How to get the keyboard out ?   <http://www.myfixguide.com/manual/lenovo-thinkpad-t500-disassembly-clean-cooling-fan-remove-keyboard/> <https://support.lenovo.com/us/en/solutions/migr-71315> <https://www.youtube.com/watch?v=qDVqKT4CyUY> <https://www.ifixit.com/Guide/Lenovo+ThinkPad+T500+Keyboard+Replacement/41037>   >What to use to bolster the keyboard on the left side. ?   Nothing. There's probably a cable out of place, or an extra long screw, or something causing the left side to lift.   -- 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

You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com.