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sam@repairfaq.org (Samuel M. Goldwasser): Aug 09 01:08PM -0400 I figured I'd post a link to this as I have recently tested a dozen or so mostly intended for Apple devices.   http://www.repairfaq.org/sam/audiofaq.htm#audipcrhg   Comments welcome.   -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html   Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.   --- sam

N_Cook <diverse@tcp.co.uk>: Aug 09 06:37PM +0100 On 09/08/2017 18:08, Samuel M. Goldwasser wrote: > ignored unless my full name AND either lasers or electronics is included in the > subject line. Or, you can contact me via the Feedback Form in the FAQs.   > --- sam   That does not include this lot, seized recently <http://www.theargus.co.uk/news/15453804.__1m_of_fake_Apple_products_seized_the__biggest_in_history_/>

sam@repairfaq.org (Samuel M. Goldwasser): Aug 09 07:13PM -0400 >> Comments welcome.   > That does not include this lot, seized recently > <http://www.theargus.co.uk/news/15453804.__1m_of_fake_Apple_products_seized_the__biggest_in_history_/>   One Web site said that something 90 percent of the Apple chargers sold on eBay were fakes. I don't know if that includes only those listed as "Genuine Apple" or just "Apple".   -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html   Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

Jeff Liebermann <jeffl@cruzio.com>: Aug 10 08:48AM -0700 On Wed, 09 Aug 2017 19:13:16 -0400, sam@repairfaq.org (Samuel M. Goldwasser) wrote:     >One Web site said that something 90 percent of the Apple chargers sold >on eBay were fakes. I don't know if that includes only those listed as >"Genuine Apple" or just "Apple".   It did include "Genuine Apple" is has become a sure sign that the adapters sold are not genuine Apple. <http://www.archersecuritygroup.com/tell-real-apple-charger-fake-life-may-depend/>   The real chargers: <https://www.apple.com/power-adapters/>   There are quite a few web sites that offer advice on how to recognize the difference between a genuine Apple charger and a counterfeit clone. Most of them use slight differences in appearance to make the determination. They never seem to mention using the weight of the charger to identify the counterfeit. I've been doing that with LiIon 18650 cells with good results using a cheap eBay scale: <http://www.ebay.com/itm/182406361786> The fake cells usually weigh less. <http://www.instructables.com/id/How-to-know-a-fake-18650-battery/>   However, I haven't tried weighing chargers. When torn apart, the counterfeit chargers tend to have much fewer components than the real charger. For example: <http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html> <http://static.righto.com/images/magsafe/top_comparison.jpg> The real Apple charger is on the left. I would expect that a fake could be identified by the weight, as long as Apple doesn't redesign the electronics, which could be identified by a change in FCCID number and model number.   You might want to get a scale, record the weights, and add them to your chart.         -- 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

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 02:43PM -0400 John-Del wrote:   > If you're referring to the resistance line cord in my example, there aren't many options even if you don't care about originality (I don't). That radio in my example has 5 tubes, two IF XFRs, a gang tuner and a dynamic speaker all crammed into a 4X10 chassis pan. The plastic cabinet covers this like a glove. There's simply no room to mount a 25W resistor or mitigate the heat that it produces.   > Still, in the trade, the resistive AC line cord was known as a "curtain burners" because people would often coil them up in a neat little ball instead of spreading them out as the owner's manual directed.   > I do restore an occasional antique radio for my customers, and even after adding fuses and polarized line cords to them, I instruct them on the dangers of line connected metal chassis and never plug in the radio if one of the plastic knobs falls off. I also instruct them to leave all old radios unplugged when not in use and to not leave them running unattended.     A small 'buck' configured transformer will reduce the filament voltage without crating a lot of waste heat.     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

John-Del <ohger1s@gmail.com>: Aug 09 01:10PM -0700 On Wednesday, August 9, 2017 at 2:43:55 PM UTC-4, Michael Terrell wrote:   > > I do restore an occasional antique radio for my customers, and even after adding fuses and polarized line cords to them, I instruct them on the dangers of line connected metal chassis and never plug in the radio if one of the plastic knobs falls off. I also instruct them to leave all old radios unplugged when not in use and to not leave them running unattended.   > A small 'buck' configured transformer will reduce the filament > voltage without crating a lot of waste heat.       Two problems: 1) there's precious little room in the radio in question for even a small buck transformer and 2) these radios are series string and have no power transformer to buck...

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 04:55PM -0400 John-Del wrote:   >> A small 'buck' configured transformer will reduce the filament >> voltage without crating a lot of waste heat.   > Two problems: 1) there's precious little room in the radio in question for even a small buck transformer and 2) these radios are series string and have no power transformer to buck...   I can understand a space problem, but you don't need a power transformer, to add a buck transformer. It is a simple autotransformer with the secondary wired anti phase, in series with the filaments. It is tiny, since the secondary only has to be the proper voltage, and it will handle the filament current. I've used them for decades, on both electronics and industrial machine tools.       -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

John-Del <ohger1s@gmail.com>: Aug 10 06:48AM -0700 On Wednesday, August 9, 2017 at 4:55:41 PM UTC-4, Michael Terrell wrote:   > I can understand a space problem, but you don't need a power > transformer, to add a buck transformer. It is a simple autotransformer > with the secondary wired anti phase, in series with the filaments.     Makes sense. The only time before this that I used a buck transformer was with another transformer. Should have given that a bit more thought. Thanks.

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 10 09:57AM -0400 John-Del wrote: >> transformer, to add a buck transformer. It is a simple autotransformer >> with the secondary wired anti phase, in series with the filaments.   > Makes sense. The only time before this that I used a buck transformer was with another transformer. Should have given that a bit more thought. Thanks.     No problem. Most people have never even heard of boost/buck transformers. :)     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

N_Cook <diverse@tcp.co.uk>: Aug 09 08:30PM +0100 I decided to convince myself of the formula. A 1 inch diameter rod of brass and some ex-draughtsmans drawing board multi-strand steel wire 0.88mm diameter. Clamped the rod and suspended the weight from the wire. 1 turn , onset of slip one way <0.5kg on a spring balance, other way >2Kg 2 turns , one way <0.2Kg , other way >6Kg. So coefficient of friction about 0.12

Mike Coon <gravity@mjcoon.plus.com>: Aug 09 11:04PM +0100 In article <omfnk8$8lp$1@dont-email.me>, diverse@tcp.co.uk says... > 1 turn , onset of slip one way <0.5kg on a spring balance, other way >2Kg > 2 turns , one way <0.2Kg , other way >6Kg. > So coefficient of friction about 0.12   I enjoyed reading the wiki formula, and noted that the diameter of the capstan/winch is not significant. Except that the cordage has to be flexible to get full friction, and the flexibility must be relative to the diameter.   Mike.

N_Cook <diverse@tcp.co.uk>: Aug 10 08:21AM +0100 On 09/08/2017 23:04, Mike Coon wrote: > flexible to get full friction, and the flexibility must be relative to > the diameter.   > Mike.   Intuitively you'd think diameter was in there. The hidden subtlety behind using multifilament steel wire on drawing tables, to retain parallelism . Once prestretched, the wire is flexible to go round half inch pulleys ,without work-hardening and breaking, 1mm solid steel wire would not. For anyone interested http://diverse.4mg.com/1924+EZ.jpg is a 1949 compilation of a few anomalous Southampton tide gauge recordings. The one of interest is the 1924 one. The original charts were lost in WW2 bombings. For the 1924 event, around midnight , not noon, as the compilation plot would have it The red overlaid trace is the predicted astronomic tide for that time. The legend "highest recorded level" is true ie highest recorded level before the mechanism jammed, end-stop hitting a pulley. Then someone added the nipple bit and gave it as the height the tide reached. But in actuality (cross-referenced from comtemporaneous newspaper reports) is something like the yellow trace, 2 inches above the ebb slope , 2 inches of slippage, meaning the tid ewas about 1.5 feet higher than what got in the records. The meteorology record of the time ,also supports something more like the yellow overlaid trace The same make of recorder at Dover also crapped out in the same storm event.

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 02:50PM -0400 Big Bad Bob wrote: > which modern components were "hidden" inside of hollowed-out > components. Maybe you can stash a modern ceramic inside of the > paper/wax tube, and seal it up with a bit of hot glue...     Ceramic capacitors are mostly cheap crap. Some have a wide change in capacitance, at different voltages. Some are microphonic, and their normal failure mode is a dead short. About the only place they should be used are for DC bybass, or in low power tuned circuits.     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

dplatt@coop.radagast.org (Dave Platt): Aug 09 12:07PM -0700 > caps made with foil, I'd prefer to use caps with foil, and whatever > plastics they used to replace the paper. In other words, I want caps > that most closely mimic the original caps, except without the paper.   Then, what you are looking for would be what's sold as "film and foil" capacitors.   Digi-Key sells e.g. the CDE "WMF" series, which use metal foil, a polyester dielectric film, "non-inductive" winding (which usually means that the foil sticks out past the end of the film, and the turns of the foil are bonded directly to the wire lead), and epoxy seals at either end. These, or similar, might be the closest thing to a "plastic drop-in replacement" for your old paper-and-foil caps.   The film-and-foil design is often preferred for applications where there's a high peak current (e.g. pulse applications) as the current carrying capability of the foil is considerable.   The other (more common) option is "metallized film". In this design, the dielectric film (polyester, polypropylene, etc.) has a thin conductive metal layer deposited on one side - typically via vaccum deposition I believe. It's not discrete particles of any real size. Two layers of this film are then spiral-wound together, with the wire leads being bonded to the leads at the ends.   Metallized-film (sometimes "stacked film") tend to be less expensive, and (I think) more capacity available per volume at any give voltage rating because the conductive layer is so thin.   They are also said to have a reliability advantage, at least potentially. If a pinhole develops in the film and two adjacent layers short together, the short-circuit current can burn away the conductive film right around the hole, "healing" the short. Apparently this only works well when the film is a material with a high oxygen content.   http://www.ecicaps.com/tech-tools/technical-papers/self-healing-affect-metallized-capacitors/

tabbypurr@gmail.com: Aug 09 01:53PM -0700 On Wednesday, 9 August 2017 19:50:17 UTC+1, Michael Terrell wrote:   > capacitance, at different voltages. Some are microphonic, and their > normal failure mode is a dead short. About the only place they should be > used are for DC bybass, or in low power tuned circuits.   Hmmm. I've not found them crap. Excluding MLCCs, which are a different animal to the rest, ceramics are immune to the melting problems of some plastic film caps, their light weight aids robustness, they're small, they typically handle way above rated voltage without trouble if ever necessary. Slight microphony is not a problem in lots of applications - it is only very slight. The C/V gotcha only applies to some, and obviously one need be aware of it at design time and choose accordingly.   All parts have their issues, and ceramics behave fine and are very reliable in a lot of situations. As with everything, not in every situation.     NT

tabbypurr@gmail.com: Aug 09 01:58PM -0700 On Wednesday, 9 August 2017 20:07:16 UTC+1, Dave Platt wrote: > Apparently this only works well when the film is a material with a > high oxygen content.   > http://www.ecicaps.com/tech-tools/technical-papers/self-healing-affect-metallized-capacitors/   Plastic film caps (but not polystyrene) are the best choice for valve radios. There is no upside in this situation to separate foils, they destabilise capacity value some, are unable to self heal, are bulkier per farad and cost more. Pick high voltage ratings to ensure they all last a lifetime.   Trying to replicate all the defects of the original caps is pointless, there is no upside to it. That isn't true of some parts but it is of caps.     NT

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 05:02PM -0400 >> used are for DC bybass, or in low power tuned circuits.   > Hmmm. I've not found them crap. Excluding MLCCs, which are a different animal to the rest, ceramics are immune to the melting problems of some plastic film caps, their light weight aids robustness, they're small, they typically handle way above rated voltage without trouble if ever necessary. Slight microphony is not a problem in lots of applications - it is only very slight. The C/V gotcha only applies to some, and obviously one need be aware of it at design time and choose accordingly.   > All parts have their issues, and ceramics behave fine and are very reliable in a lot of situations. As with everything, not in every situation.       If the originals were paper, I always use film capacitors. I've had too many shorted Ceramics in HV circuits, and I've replaced too many shorted disk capacitors in 5V circuits. Some have burnt holes in PC boards, when they are on a high current rail. "The C/V gotcha" can cause distortion in audio circuits, or cause an AGC circuit to 'pump'.     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

tabbypurr@gmail.com: Aug 09 05:15PM -0700 On Wednesday, 9 August 2017 22:02:04 UTC+1, Michael Terrell wrote: > shorted disk capacitors in 5V circuits. Some have burnt holes in PC > boards, when they are on a high current rail. "The C/V gotcha" can cause > distortion in audio circuits, or cause an AGC circuit to 'pump'.   Those last 2 are examples of using them where not suited. If I use ceramics as audio decoupling they need to either not have the C/V gotcha or be big enough to still have enough capacity down at 20Hz to not get in the way AND the dc component across them needs to remain steady.     NT

rickman <gnuarm@gmail.com>: Aug 09 09:00PM -0400 >> boards, when they are on a high current rail. "The C/V gotcha" can cause >> distortion in audio circuits, or cause an AGC circuit to 'pump'.   > Those last 2 are examples of using them where not suited. If I use ceramics as audio decoupling they need to either not have the C/V gotcha or be big enough to still have enough capacity down at 20Hz to not get in the way AND the dc component across them needs to remain steady.   The C/V "gotcha" is best mitigated by using a part that is overrated for voltage. The C/V effect is relative to the rated voltage so if that is several times the circuit voltage there won't be much effect. It's when you try to operate near the rated voltage that it causes problems. I've also seen data that indicates the larger package parts have lower coefficients of capacitance change with voltage.   You can also use C0G types which have a better dielectric which has a very low coefficient of capacitance change with voltage.   --   Rick C

tabbypurr@gmail.com: Aug 09 06:37PM -0700 On Thursday, 10 August 2017 02:00:07 UTC+1, rickman wrote: > voltage. The C/V effect is relative to the rated voltage so if that is > several times the circuit voltage there won't be much effect. It's when you > try to operate near the rated voltage that it causes problems.   Picking a random Y5V, C is down to just 20% at 40% rated V, 40% C at 20% rated V. John Larkin tested a 4.7uF 50v cap and found 0.8uF at 30v, 1.33uF at 20v, 2.86uF at 10v. It was down over 90% at rated V, 0.42uF.   > capacitance change with voltage.   > You can also use C0G types which have a better dielectric which has a very > low coefficient of capacitance change with voltage.   Of course. But one doesn't need C0G for run of the mill decoupling, bypassing etc.     NT

rickman <gnuarm@gmail.com>: Aug 09 10:26PM -0400 >> try to operate near the rated voltage that it causes problems.   > Picking a random Y5V, C is down to just 20% at 40% rated V, 40% C at 20% rated V. > John Larkin tested a 4.7uF 50v cap and found 0.8uF at 30v, 1.33uF at 20v, 2.86uF at 10v. It was down over 90% at rated V, 0.42uF.   Yeah, if you are going to pick the worse possible type of cap it won't work as well. Try an X5R type and it works a lot better.       >> You can also use C0G types which have a better dielectric which has a very >> low coefficient of capacitance change with voltage.   > Of course. But one doesn't need C0G for run of the mill decoupling, bypassing etc.   ????   --   Rick C

Jim Mueller <wrongname@nospam.com>: Aug 10 02:47AM On Wed, 09 Aug 2017 04:54:25 -0700, Big Bad Bob wrote:   > which modern components were "hidden" inside of hollowed-out components. > Maybe you can stash a modern ceramic inside of the paper/wax tube, and > seal it up with a bit of hot glue...   It will be tough to find good ceramics in the values listed with voltage ratings high enough for tube gear. Polyester (Mylar) or Polypropylene are better choices.   As for the quality of ceramic capacitors, it depends on what kind of ceramic is used. C0G ceramics are about the best capacitors you can easily get. They are very stable, have very low loss, and are excellent in just about every other way. The one way they are not excellent is that, except for low values (less than around 1000pF - depends on manufacturer) they are large and expensive. Mid grade ceramics like X7R are less stable and less expensive. They are suitable for most audio frequency work. The really bad ceramics are the ones like Z5U. They are truly horrible in most ways and are suitable only for non-critical circuits like supply bypassing. They are, however, tiny and very cheap. Go to the manufacturer's data sheet for the capacitors you want to use to see if their characteristics match the application.       -- Jim Mueller wrongname@nospam.com   To get my real email address, replace wrongname with eggmen. Then replace nospam with expressmail. Lastly, replace com with dk.

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 02:24PM -0400 > It can happen with a simple picture like the station call letters when the scene lighting is such that the left of the picture is brighter then the right , and you have the scope set to the V rate.   > or something like that,   > it is eerie.     Some simple hand drawn cartoons would do that on a waveform monitor at the AFRTS TV station zi worked at in the '70s. I saw 'Quickdraw McGraw walk across the screen of a Tektronix RM529 more than once. :)   -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

"Michael A. Terrell" <mike.terrell@earthlink.net>: Aug 09 02:13PM -0400 > Mpfffff...   > No, I do not do precision work, which, in point-of-fact is probably the case as the typical Zenith or Hallicrafters or Tesla or SNR radio is not a precision instrument. But, they do just fine aligning with a Fluke meter ILO a VTVM.   > Nor, of course does Old School. And, given his posts, is likely defeated by anything more complex than a rubber spoon. .   You're trolling, as always.     -- Never piss off an Engineer!   They don't get mad.   They don't get even.   They go for over unity! ;-)

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