sci.electronics.repair@googlegroups.com

Google Groups

ggherold@gmail.com: Oct 19 06:51AM -0700 Hi all, I found this thing.. see pictures   https://www.dropbox.com/sh/sxd1cq8qbdyali4/AAA6O9NqKQPvbX4QLzNAK-Vaa?dl=0 In the back of a drawer at my house. The previous owner was a pack rat, who also worked for the phone company. It looks like some high voltage flashlight. What sort of voltage do I apply to the leads?   Thanks, George H.

Boris Mohar <borism_void_@sympatico.ca>: Oct 19 10:03AM -0400 >What sort of voltage do I apply to the leads?   >Thanks, >George H.   It could be automotive timing light. -- Boris   --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

ggherold@gmail.com: Oct 19 07:10AM -0700 On Monday, October 19, 2015 at 10:03:35 AM UTC-4, Boris Mohar wrote:   > It could be automotive timing light. > -- > Boris   Ahh OK, That's a good guess.   Thanks, George H.

"pfjw@aol.com" <pfjw@aol.com>: Oct 19 07:31AM -0700 > What sort of voltage do I apply to the leads?   > Thanks, > George H.   As per Boris - yes, it could be a timing light - but definitely a stop-action device of some sort. I expect that there were other parts associated with it - strobe-type timing lights have an induction trigger device, usually, as one example. + & -attached to the battery, and the inductor clamped to #1 cylinder spark-plug wire.   Peter Wieck Melrose Park, PA

Cursitor Doom <curd@notformail.com>: Oct 18 06:08PM On Wed, 14 Oct 2015 20:11:26 -0700, Phil Allison wrote:     > ** Impossible in fact, but clipping wave peaks is just what tube guitar > amps do most of all the time and blown speakers are very common - due > again to high average power levels.   Makes sense the way you've explained it, Phil. I had a Technics amp one time that just ate through speakers for some reason; all top quality KEF units as well. :( The only thing I could come up with for a cause was that the amp sound was very 'cold' - typical of Technics amps - so may have been producing transients the speakers couldn't handle. But that's no more than a hunch. The other thing the OP seems to be unaware of is that the term 'RMS power' is really indefinable anyway. You can't take the product of RMS voltage and RMS current (which are both valid measurements) and derive 'RMS power' from them. We should drop the use of this non-sensical term and adopt 'average power' instead. And as for 'total peak music power' - bah! Don't get me started! ;->

thekmanrocks@gmail.com: Oct 18 02:52PM -0700 pf...@aol.com wrote: "- show quoted text - OK - a few basics on speakers - at least as they were sold in the US under FTC regulations (sit on your fingers, Phil!): "     Additionally, correct me if I'm wrong, but the "sticker" impedance(ohms) is the lowest reading for a speaker, across the audio spectrum.

Phil Allison <pallison49@gmail.com>: Oct 18 07:05PM -0700 Cursitor Doom wrote:   > that the amp sound was very 'cold' - typical of Technics amps - so may > have been producing transients the speakers couldn't handle. But that's > no more than a hunch.   ** Not much of a one.   People like to blame the amplifier when a speaker fails - but if it still works fine, it is almost certainly blameless.     > The other thing the OP seems to be unaware of is that the term 'RMS > power' is really indefinable anyway.   ** The term simply refers to "watts rms" which has always meant the power rating is based on the rms value of the sine wave used for the test.   A much clearer term is "continuous sine wave power", but that is inconveniently long.     .... Phil

Phil Allison <pallison49@gmail.com>: Oct 18 07:25PM -0700 > Additionally, correct me if I'm wrong, but the "sticker" > impedance(ohms) is the lowest reading for a speaker, > across the audio spectrum.   ** For individual woofers and full range drivers that is normally so - a woofer labelled "8ohms" has about 6.5 ohms of resistance and tests 8 ohms only around 250 to 400Hz.   But it's not generally true for speaker systems where the crossover network can introduce impedance variations both above and below the nominal figure.     .... Phil

"pfjw@aol.com" <pfjw@aol.com>: Oct 19 07:08AM -0700 On Wednesday, October 14, 2015 at 11:11:32 PM UTC-4, Phil Allison wrote:   > > OK - a few basics on speakers - at least as they were sold in the > > US under FTC regulations (sit on your fingers, Phil!):   > ** The are simply no FTC rules for published speaker power ratings. The rules you seem to be alluding to are for *amplifers* used in home entertainment.   Let's clarify, then. US speaker manufacturers very rapidly adapted to the FTC rules when publishing their ratings. Prior to these rules, IPP was the way amp makers would fool their buyers, and speaker makers would do their ratings similarly. As things equalized, their ratings became much more realistic. > > it may send straight DC into the speaker   > ** Absurd.   > Clipping does not cause DC, the main effect is to compress the dynamic range of the music so there is more average power going to the speaker - which eventually overheats the voice coil.   If you can, next time you are out on the street, see if you can borrow either of a Dynaco ST80, ST120, AR amplifier, any of several Scott/Fisher/Sherwood solid-state designs, any any of many pacific-rim solid-state designs that used discrete output transistors, a Revox B722 - the list goes on. Drive it to clipping. At clipping you will see serious DC at the outputs. This will 'freeze' the VC(s) in one position with lots-O-energy at the same time. Not generally a good idea.   > > This issue is far less so from a tube amp - the simplistic explanation is >that it is harder for a transformer to pass DC,   > ** Impossible in fact, but clipping wave peaks is just what tube guitar amps do most of all the time and blown speakers are very common - due again to high average power levels. Instrument amps blow speakers for many different reasons - and even a transformer will transfer chopped DC. Hence the term "simplistic". But instrument amps are a balance of many things. I have always wondered why the makers do not use much heavier speakers than they do - I guess it is a cost/benefit thing. But musicians using such devices seldom care much about fidelity - being more interested in noise and effects. And they generally operate at the bleeding edge.   A well-designed amplifier not driven to clipping into well-designed speakers not driven at ear-bleed levels will generally be safe forever, or at least until the one or the other device fails for other reasons than being over-driven. But I betcha I could do more damage to my AR3a or Maggie speakers with the 40-watt solid state amp than with the 17-watt or 75-watt tube amp - these representing my most rugged speakers being rated at 100 and 200 watts respectively.   Point being that not all devices are safe across the board. And many legacy/vintage devices are flatly unsafe if abused. The typical user these days believes that decent sound can come from a highly compressed source into computer speakers and/or earbuds, and have probably never heard a decent system under decent conditions with decent signal. Nor do they have a clue about Clipping, and what it actually means, nor its relationship to perceived volume and power requirements to achieve it. So, off they go trying to shake the floor or rattle the windows with a 4" speaker...   Peter Wieck Melrose Park, PA

4thrs <ynot4me@gmail.com>: Oct 19 02:32AM -0700 Has anyone got, or know where I can purchase, a schematic diagram, for this TV, Power Supply Board, CVB42001. This board is commonly used in LED TVs. I'm chasing a problem in the output voltage, that feeds the LEDs Strips. Tks.

Cursitor Doom <curd@notformail.com>: Oct 18 05:50PM On Sun, 18 Oct 2015 10:12:17 +0100, Mike Tomlinson wrote:   > yomoyco@gmail.com escribió:   >>el valor de r602 es 22 ohms a 1w   > felicidades por responder a un mensaje de 18 años de edad!   LOL! That must be some kind of record!

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.