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oldschool@tubes.com: Apr 22 01:35AM -0400 I'm looking at a repair manual for a high powered transistorized audio amplifier. It repeatedly says:   DO NOT use any test equipment to test or evaluate this amplifier, which does not have floating grounds.   If the DC voltmeter is AC powered, Float the AC ground wire.   I (sort of) understand what they mean by a "Floating Ground", but I'm not exactly sure what they mean. And, if I was to use a VTVM which is plugged into the AC line, or an Oscilloscope (also plugged into an outlet), how do I achieve a "floating ground"?   Now, lets say I use a pocket battery operated VOM. It's not plugged in, so there is no ground. Is that safe to use on this device? (Seems to me that a pocket VOM is NOT actually grounded to earth, so that WOULD be a floating ground. (I think)....

Phil Allison <pallison49@gmail.com>: Apr 21 11:54PM -0700 The Old Fart wrote: > not exactly sure what they mean. And, if I was to use a VTVM which is > plugged into the AC line, or an Oscilloscope (also plugged into an > outlet), how do I achieve a "floating ground"?   ** You can't do it with good safety.   Disconnecting the AC ground does it unsafely.     > so there is no ground. Is that safe to use on this device? (Seems to me > that a pocket VOM is NOT actually grounded to earth, so that WOULD be a > floating ground. (I think)....   ** Of course.   The amp uses bridge mode output - right ?   So both speaker terminals are amp outputs.   So all YOU do is measure one of them to ground with your VTVM or scope and double the reading.     ..... Phil

thekmanrocks@gmail.com: Apr 22 03:07AM -0700 olds...@tubes.com:   Floating ground = shared, at least in my experience.   On my early '80s GM stock stereo, there were speaker outputs for four speakers as follows:   Left-Front Positive, Left-Rear Positive, and a single Left-Minus(both left speakers Minus wires tied into that). Ditto on the Right. It was called 'floating' ground because there weren't individual negative leads for the front and rear speakers on each side.   Probably done to save space and money by using less copper.

Adrian Caspersz <email@here.invalid>: Apr 22 11:16AM +0100 > not exactly sure what they mean. And, if I was to use a VTVM which is > plugged into the AC line, or an Oscilloscope (also plugged into an > outlet), how do I achieve a "floating ground"?   Use a safety isolation transformer, or batteries.   -- Adrian C

Phil Allison <pallison49@gmail.com>: Apr 22 03:23AM -0700 Adrian Caspersz wrote:       > Use a safety isolation transformer, or batteries.     ** FFS - that IS absurd advice from another fucking, know nothing "phrase matching" idiot.       .... Phil

whit3rd <whit3rd@gmail.com>: Apr 22 03:50AM -0700 > amplifier. It repeatedly says:   > DO NOT use any test equipment to test or evaluate this amplifier, which > does not have floating grounds.   Possibly it means that the 'ground' terminals are actually connected to the AC neutral wire (not to a third-wire ground). That connection is permitted only with limiting resistance so that shock hazard is nil, but 'test equipment' can easily see high-voltage transients.   That would make sense only if this is a two-wire AC powered gizmo. It would make MORE sense if the device were an old TV set.

Phil Allison <pallison49@gmail.com>: Apr 22 04:00AM -0700 whit3rd wrote:   > but 'test equipment' can easily see high-voltage transients.   > That would make sense only if this is a two-wire AC powered gizmo. > It would make MORE sense if the device were an old TV set.   ** You know something, just because you see a question posted on this NG - that does not mean you have to try an answer it.   FFS - it was not posted to you.   If you haven't got a clue - shut the fuck up.       .... Phil

Adrian Caspersz <email@here.invalid>: Apr 22 02:01PM +0100 On 22/04/17 11:23, Phil Allison wrote: > Adrian Caspersz wrote:   >> Use a safety isolation transformer, or batteries.   > ** FFS - that IS absurd advice from another fucking, know nothing "phrase matching" idiot.   Use of a mains isolation transformer allows a safe floating ground reference. I've done that with 'scopes on a live television chassis, with a 500W lump of a 240V/240V transformer.   Nice day outside?   -- Absurd C

Foxs Mercantile <jdangus@att.net>: Apr 22 08:21AM -0500 On 4/22/2017 1:54 AM, Phil Allison wrote: > The amp uses bridge mode output - right ?   > So both speaker terminals are amp outputs.   I'm going to go with this as the correct answer. The audio output of a Motorola Spectra is like this, and there are warnings repeatedly through the service manual NOT to ground either side of the audio.   This has nothing to do with "hot chassis" or floating grounds.     -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com   --- This email has been checked for viruses by AVG. http://www.avg.com

Ralph Mowery <rmowery28146@earthlink.net>: Apr 22 10:28AM -0400 In article <7cqlfcp3p9t9pu6f192morv3991n86bidl@4ax.com>, oldschool@tubes.com says... > so there is no ground. Is that safe to use on this device? (Seems to me > that a pocket VOM is NOT actually grounded to earth, so that WOULD be a > floating ground. (I think)....   There are 2 possibilities. The first one that comes to mind is the 'hot chassis' where one side of the AC line is connected to the chassis. Usually an isolation transformer is used, or battery powered instruments that do not have a ground or conductive case.   The other is for mainly transistor audio output amplifiers. The speaker has both leads floating above ground. If a meter is used that one side of the test leads go to the chassis and the chassis of the meter is grounded by the 3 wire AC plug, the amp will be dammaged.   The same for the battery powered meter applies. If it does not have a conductive chassis and no AC line cord then you can use it.     Another rare,but possiable case is that a 'ground loop' can be made where a lot of hum or other undesired signals can be made.

avagadro7@gmail.com: Apr 21 09:47AM -0700 Suggest circuits for linking an analog amp gauge to the output of a 200 amp auto alternator for measuring output under load. ? links ? commercial units ?

bobrweber@gmail.com: Apr 21 10:56AM -0700 > Suggest circuits for linking an analog amp gauge to the output of a 200 amp auto   > alternator for measuring output under load. ? links ? commercial units ?   I use a Klein tools 400A AC/DC True RMS Clamp Meter model CL2000. Just clamp around the battery/alternator cable to see the charging/discharging amps. The resolution is good for the <20A range I usually use it for. The model seems to be out of production but their model cl800 appears to be a replacement ($105 on amazon). There are some clamp-on meters on ebay but watch out that they do measure dc amps in clamp-on mode.

ohger1s@gmail.com: Apr 21 01:14PM -0700 > Suggest circuits for linking an analog amp gauge to the output of a 200 amp auto   > alternator for measuring output under load. ? links ? commercial units ?     Do you have the ammeter? If you have the ammeter in hand, you can get the hookup instructions on line. If the ammeter is too low a current, you can add a shunt. Check DigiKey.   In any case, I'd rather not have an ammeter handle the full current mounted in the dashboard if that's your plan.

Bennett <bjprice@cal.berkeley.edu>: Apr 21 02:56PM -0700 >> alternator for measuring output under load. ? links ? commercial units ?   > Do you have the ammeter? If you have the ammeter in hand, you can get the hookup instructions on line. If the ammeter is too low a current, you can add a shunt. Check DigiKey.   > In any case, I'd rather not have an ammeter handle the full current mounted in the dashboard if that's your plan.   Or just buy something like this: https://www.ebay.com/p/?iid=142207111925&lpid=82&&&ul_noapp=true&chn=ps and hook it up in series with the alternator, i.e., in between the alternator and the heavy wire which presently comes from the alternator. If the needle goes in the wrong direction, just reverse the wiring.

avagadro7@gmail.com: Apr 21 05:25PM -0700 Not full. A sampling device connected to an auto amp gauge. For example, the gauge may read 10 amps on a full sweep. Is this too much for outside the dash ? How is this done if it is done on a Kenworth ?   The alt is 200 amps above 65 mph.   There are TSD factors using stereo 40 amp fuse, lights @ 30 amps, vehicle OP amps @ 75 ... where quantifying the load vs miles to go vs a positive battery charge is useful. Better than. 'geee whiz the lights are yellowing' ... as too late n that is 3 hours with no aux load to reach white light again?

Phil Allison <pallison49@gmail.com>: Apr 22 12:13AM -0700 > Suggest circuits for linking an analog amp gauge to the output of a 200 amp auto   > alternator for measuring output under load. ? links ? commercial units ?   ** Do you still have other people wipe you arse for you ?   Wot a lazy fucking shit.   http://www.madelectrical.com/electricaltech/images/amp-ga18.jpg

avagadro7@gmail.com: Apr 22 06:44AM -0700 On Saturday, April 22, 2017 at 3:13:45 AM UTC-4, Phil Allison wrote:   > ** Do you still have other people wipe you arse for you ?   > Wot a lazy fucking shit.   > http://www.madelectrical.com/electricaltech/images/amp-ga18.jpg   PHOOOOM !   why the fuse box connection ?   all ...probably all...today's aux system are separate from the factory computer except for the trailer wiring harness.   The Ford truck computer system is fairly tolerant of low power experiment. Blowing fuses not massive $$$$. EG skip the ignition measure n assume 75 to 100   What I would need with your link is a reduction of 100 amps...the alleged supply over operation Ford amps with 'stock' lights on ... to 1 amp at the gauge. A quality one amp gauge linear to the 100 amps. I assume linearity.   Inserting a resistor ? is this OK or is there a better way of sampling 100 to 1 amp ?

erilira@gmail.com: Apr 22 02:58AM -0700 Em sexta-feira, 30 de maio de 2014 15:01:59 UTC+2, Leif Neland escreveu:   > -- > Husk kï¿œrelys bagpï¿œ, hvis din bilfabrikant har taget den idiotiske > beslutning at undlade det.   hi i have a problem with my husqvarna 315, the LCD screen has the error No Loop signal and the light in the charger is strong green.   thanks

Jeroni Paul <JERONI.PAUL@terra.es>: Apr 21 04:59PM -0700 Phil Allison wrote:   > R615 ( 0.22 ohms 2 watts ) must be a metal film or composition type.   > IOW *low* inductance is crucial.   > ..... Phil   Thank you Phil. The resistor you mention was good and is the original. Finally I got it working by wiring 4 100W bulbs in parallel, so I removed the bulbs and all is fine.

Phil Allison <pallison49@gmail.com>: Apr 21 07:22PM -0700 Jeroni Paul wrote:   > The resistor you mention was good and is the original. > Finally I got it working by wiring 4 100W bulbs in parallel, > so I removed the bulbs and all is fine.   ** That SMPS is unusually sensitive to low AC supply voltage.   Normally they work from 85V and up.       .... Phil

"J.B. Wood" <arl_123234@hotmail.com>: Apr 21 12:50PM -0400 Hello, all. These days the subject cells from various manufacturers are sold as one type, silver oxide 357/303. Seems like they must have been distinct types at one time and if so, how did they differ? Couldn't seem to find anything historically on line. Thanks for your time and comment. Sincerely, -- J. B. Wood e-mail: arl_123234@hotmail.com

Bennett <bjprice@cal.berkeley.edu>: Apr 21 03:22PM -0700 On 4/21/2017 9:50 AM, J.B. Wood wrote: > distinct types at one time and if so, how did they differ? Couldn't > seem to find anything historically on line. Thanks for your time and > comment. Sincerely, My ancient ca. 1985 Panasonic battery manual says the 357 is for High Drain (180 mAh) and the 303 for Low drain 170 mAh uses. The 303 is 0.2 mm taller than the 327 5.60mm vs. 5.40mm   Why is the low drain taller than the high drain? I've no idea.   Further complicating things is that Panasonic lists the National SR44W as equivalent to the SP357; the National SR47SW as the equal of the SP303 Panasonic says the W suffix is for high drain use - LCD & multi-function analog watches. SW suffix for low drain single-function analog watches. But Panasonic doesn't label any of its silver-oxide batteries with W or SW. The suffixes, Panasonic says, indicate different types of caustic potash electrolyte. Presumably, I guess, Panasonic uses these 2 different electrolytes but doesn't add W or SW to its labels.

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