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jurb6006@gmail.com: Aug 01 01:32PM -0700 >"It is very instructive when using a THD analyser to view the residual signal on a scope - so you know what it consists of. "   I assume that is what is at the "monitor" terminals. Is that correct ? Iff thsat is what it is I would like to have a scope connected there, or later when I get one, a spectrum analyzer maybe ?

jurb6006@gmail.com: Aug 01 01:41PM -0700 >"You can take that and add it to the original sine wave via voltage >dividers (a decade resistance box would be useful), and calibrate the >meter down as low as you like. 90% sine + 10% square = 4.84% THD, etc. "   Very interesting. Once I got the thing to the point where I think it works I will have to look into that. An actual ay to calibrate it, though not really accurate it does prove it works. Maybe with a little bit of trouble it can be confirmeed down to a certain resolution.   The Wavetek has a fixed square wave (in fact all of them) and a variable output that is selectable. Couple of resistors should do it.   So 90/10 should read 48.4 %. That means 99/1 should read 4.84 % ?   Question - am I going by peak value or RMS/average or what here ?

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 01 05:02PM -0400 > variable output that is selectable. Couple of resistors should do > it.   > So 90/10 should read 48.4 %. That means 99/1 should read 4.84 % ?   On a voltage basis, 100% square is 48.4, 10% square is 4.84, 1% square is 0.484, 0.1% square is 0.0484, and so on. (On one definition of THD it's slightly inaccurate at 10% because there's only 98% of the sine power at that point, but it's the lower numbers you care about anyway.)     > Question - am I going by peak value or RMS/average or what here ?   From a signal processing POV, the THD meter reading is the square root of SINAD, i.e. the ratio of (everything except the sine wave)/(the sine wave) on an amplitude basis, not a power basis like a SNR or SINAD. I gave the definition in my last post.   The intention is to have a number you can read off on a scope, so it's basically voltage. You can't usefully add up the amplitudes of different frequency components, so the audio THD definition uses the square root of the power rather than the voltage per se. You can think of it as RMS distortion divided by RMS signal.   Cheers   Phil Hobbs         -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Phil Allison <pallison49@gmail.com>: Aug 02 01:10AM -0700 Phil Hobbs wrote:     > One simple method is to wire up a comparator to turn the internal > oscillator signal into a square wave.   ** One needs a test that shows the instrument is doing the things a THD analyser is meant to.   1. Thoroughly remove the fundamental frequency.   2. Pass other frequencies up to 100kHz to the metering circuit.   Frequency sweeps from 20Hz to 100kHz will verify this - with the instrument set to notch a variety of spot frequencies in the audio band.   The notch should be sufficiently narrow at each test point that little attenuation exists at half and double the centre frequency and beyond up to a -3dB point at 100kHz.     ... Phil

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 02 07:39AM -0400 On 8/2/2015 4:10 AM, Phil Allison wrote: > THD analyser is meant to.   > 1. Thoroughly remove the fundamental frequency.   > 2. Pass other frequencies up to 100kHz to the metering circuit.   And   3. Measure distortion accurately.   The square wave/attenuator trick does all of that.     > The notch should be sufficiently narrow at each test point that > little attenuation exists at half and double the centre frequency and > beyond up to a -3dB point at 100kHz.   (I actually own an HP 339A but haven't used it for anything serious.)   Cheers   Phil Hobbs     -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Phil Allison <pallison49@gmail.com>: Aug 02 05:33AM -0700 Phil Hobbs wrote: Phil Allison wrote:       > And   > 3. Measure distortion accurately.   > The square wave/attenuator trick does all of that.     ** Like hell it does.       > > little attenuation exists at half and double the centre frequency and > > beyond up to a -3dB point at 100kHz.   > (I actually own an HP 339A but haven't used it for anything serious.)     ** That is very obvious.     ... Phil

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 02 09:13AM -0400 On 8/2/2015 8:33 AM, Phil Allison wrote:   >> 3. Measure distortion accurately.   >> The square wave/attenuator trick does all of that.   > ** Like hell it does.   Really? Why not?   If the indicated distortion gets down to the noise floor, the fundamental has to be gone to that level, which satisfies #1.   If the indicated reading is correct and stable over frequency, then the notch isn't attenuating the third harmonic. Some more asymmetric rectangle would get you the second harmonic, but those are a bit more difficult to calculate, especially for a technician. So #2 could be improved, but is probably fine if the filter is actually working.   And nothing in your method addresses #3, the accuracy question, whereas the THD of a square wave is known very accurately, and an attenuator allows you to make accurate distortion standards down right into the mud. What's not to like?   Cheers   Phil Hobbs     -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Wond <gboot.phil@gmx.com>: Aug 02 02:54PM On Sat, 01 Aug 2015 13:32:53 -0700, jurb6006 wrote:     > I assume that is what is at the "monitor" terminals. Is that correct ? > Iff thsat is what it is I would like to have a scope connected there, or > later when I get one, a spectrum analyzer maybe ?   The 339A manual is on the BAMA site at edebris.com

John Robertson <spam@flippers.com>: Aug 01 09:47AM -0700 On 08/01/2015 9:18 AM, MJC wrote:   >> thanks.   > Electric eel?   > Mike.   All my fish preferred 0V...otherwise it was just a tank full of floaters.   John ;-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

Cursitor Doom <curd@notformail.com>: Aug 01 06:34PM On Sat, 01 Aug 2015 09:47:48 -0700, John Robertson wrote:     > All my fish preferred 0V...otherwise it was just a tank full of > floaters.   > John ;-#)#   Oh yes, jolly amusing. I was of course talking about TF capacitors. I think I may have fried one accidentally by careless use of a variac. Something on the board I was testing made a muffled sizzling sound for several seconds and I'm trying to establish what I damaged. There are no visual signs of damage and I didn't see any smoke at the time; just heard that noise.

"Gareth Magennis" <sound.service@btconnect.com>: Aug 01 09:11PM +0100 "Cursitor Doom" wrote in message news:mpj3fg$fm5$1@dont-email.me...   On Sat, 01 Aug 2015 09:47:48 -0700, John Robertson wrote:     > All my fish preferred 0V...otherwise it was just a tank full of > floaters.   > John ;-#)#   Oh yes, jolly amusing. I was of course talking about TF capacitors. I think I may have fried one accidentally by careless use of a variac. Something on the board I was testing made a muffled sizzling sound for several seconds and I'm trying to establish what I damaged. There are no visual signs of damage and I didn't see any smoke at the time; just heard that noise.           I think it unlikely that any component on that board will not be designed to tolerate 10% above the voltage expected. The figures you quote are around 6%.     Be wary of jumping to conclusions. Just because component X dies just as you made a cup of tea does not mean the cup-of-tea-making caused the failure of said component.         Gareth.

John Robertson <spam@flippers.com>: Aug 01 01:13PM -0700 On 08/01/2015 11:34 AM, Cursitor Doom wrote: > testing made a muffled sizzling sound for several seconds and I'm trying > to establish what I damaged. There are no visual signs of damage and I > didn't see any smoke at the time; just heard that noise.   Well, not knowing what you were talking about as the thread was long dead (always best to quote) we had no clue as to what you were talking about and did have a little fun.   As for your caps - check the absolute maximum voltage rating. If you exceeded it then chances are the caps need replacing.   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

John Robertson <spam@flippers.com>: Aug 01 01:21PM -0700 On 08/01/2015 11:34 AM, Cursitor Doom wrote: > testing made a muffled sizzling sound for several seconds and I'm trying > to establish what I damaged. There are no visual signs of damage and I > didn't see any smoke at the time; just heard that noise.   Oh, Tropical Fish Capacitors - you know I've seen those in many an old radio but never heard them called that.   Interesting.   How well it would take any voltage depends on the seal - if any moisture has leaked in (likely) then the breakdown voltage would drop.   Something that old is probably best replaced with a modern capacitor IMHO.   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

Cursitor Doom <curd@notformail.com>: Aug 01 08:39PM On Sat, 01 Aug 2015 13:21:55 -0700, John Robertson wrote:   > How well it would take any voltage depends on the seal - if any moisture > has leaked in (likely) then the breakdown voltage would drop.   That could be relevant, then. These old TFs had hairline cracks in them at the sides. I touched one with the tip of a screwdriver and a flake fell away exposing the edge of the plates and the dilectric. So yes, they should certainly be replaced and if as you say that crack would have let moisture in, then 260V might easily have killed it. Hopefully we have the culprit. :-/

Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Aug 01 11:09PM +0200 On 01.08.15 20:34, Cursitor Doom wrote: > testing made a muffled sizzling sound for several seconds and I'm trying > to establish what I damaged. There are no visual signs of damage and I > didn't see any smoke at the time; just heard that noise.   That was an electrolytic cap, boiling off the liquid inside.

Cursitor Doom <curd@notformail.com>: Aug 02 11:44AM On Sat, 01 Aug 2015 23:09:52 +0200, Sjouke Burry wrote:   > That was an electrolytic cap, boiling off the liquid inside.   I like your thinking; sound entirely feasible. I'll check them all out.

Cursitor Doom <curd@notformail.com>: Aug 02 02:45PM On Sun, 02 Aug 2015 11:44:42 +0000, Cursitor Doom wrote:   > On Sat, 01 Aug 2015 23:09:52 +0200, Sjouke Burry wrote:   >> That was an electrolytic cap, boiling off the liquid inside.   > I like your thinking; sound entirely feasible. I'll check them all out.   They've all checked out fine. The TFs remain the prime suspects.

Phil Allison <pallison49@gmail.com>: Aug 01 06:29PM -0700 Cursitor Doom wrote:   > Just one final point. Is a single sine wave sufficient, or will it have > to be two, harmonically-unrelated sine waves?     ** A single sine wave is needed for audio power testing.   Amplifier power ratings are based on the *rms* value of a sine wave - hence the misleading term "rms power".     > ISTR with RF power > measurements you need to perform the slightly more complicated 'two-tone' > test; just wondering if the same applies at audio frequencies?   ** Using two tones tests for intermodualtion, always present where there is non-linearity.     .... Phil

Cursitor Doom <curd@notformail.com>: Aug 02 11:49AM On Sat, 01 Aug 2015 18:29:58 -0700, Phil Allison wrote:   > ** A single sine wave is needed for audio power testing.   > Amplifier power ratings are based on the *rms* value of a sine wave - > hence the misleading term "rms power".   Well that would make sense with RMS being, IIRC, equivalent to the DC heating effect in a resistive load.

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Aug 02 09:04AM -0400 On 8/2/2015 7:49 AM, Cursitor Doom wrote: >> hence the misleading term "rms power".   > Well that would make sense with RMS being, IIRC, equivalent to the DC > heating effect in a resistive load.   RMS is an amplitude, e.g. 'volts RMS'. Phil's right that the term is in error, but there's so many lies and so much snake oil in the audio business that this minor absurdity seems a fairly small price to pay to clear away all the "peak intermittent music power" (PIMP) nonsense. ;)   Cheers   Phil Hobbs       -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Cursitor Doom <curd@notformail.com>: Aug 02 01:29PM On Sun, 02 Aug 2015 09:04:54 -0400, Phil Hobbs wrote:   > RMS is an amplitude, e.g. 'volts RMS'.   Yes, I recall 0.707 of the peak signal level. So for example if I set an amp to some arbitrary output and feed into an 8 ohm load and measure say 10V peak-to-peak on a scope, then I'm getting about 6.25W RMS out.   Phil's right that the term is in > error, but there's so many lies and so much snake oil in the audio > business that this minor absurdity seems a fairly small price to pay to > clear away all the "peak intermittent music power" (PIMP) nonsense. ;)   Fully agree with you on that!

Cursitor Doom <curd@notformail.com>: Aug 02 01:41PM On Sun, 02 Aug 2015 13:29:38 +0000, Cursitor Doom wrote:   >> clear away all the "peak intermittent music power" (PIMP) nonsense. >> ;)   > Fully agree with you on that!   Should have put the 6.25W RMS in inverted commas, since there's no such thing as RMS power, of course. It's really all about *average* power.

avagadro7@gmail.com: Aug 01 03:47PM -0700 On Wednesday, April 29, 2015 at 10:40:25 PM UTC-4, Jon Elson wrote: > this for years, and my PVC cement usually lasts a couple years before drying > out. You WILL need the wrench to get it open the next time, though.   > Jon   pump wrench http://i00.i.aliimg.com/photo/v1/144680916/Water_Pump_Wrench.jpg   cut a square of Walmart grocery bag, pierce a mid hole if the cap has a brush..   cover can with bag square so threads are covered screw lid on then tweak threads tight with pump wrench.   comes apart with pump wrench. store wrench in cool place.   what's a wall wart ? I repair lead separation on charger units with liquid electrical tape. Splint the wire n cover area with tape goooo. Grainger has the good stuff. Handy shelf barnacle

avagadro7@gmail.com: Aug 01 03:51PM -0700 On Wednesday, April 29, 2015 at 10:51:28 PM UTC-4, Jeff Liebermann wrote: > 150 Felker St #D http://www.LearnByDestroying.com > Santa Cruz CA 95060 http://802.11junk.com > Skype: JeffLiebermann AE6KS 831-336-2558   use the bag. roll up the tube bottom when using just like on TV forcing the air out, place small bag square over outlet then screw cap just so before closing while squeezing the bottom of tube at the rollup focing last air out while snuuging the cap down tight.   I split caps...keep a box of spares with the paint nozzles and bag ties

Jeff Liebermann <jeffl@cruzio.com>: Aug 02 12:28AM -0700 >what's a wall wart ?   <https://www.google.com/search?tbm=isch&q=wall+wart>   A large one is a "power brick": <https://www.google.com/search?tbm=isch&q=power+brick>   -- 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

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