Re: capacitor leakage go/no-go test
A curve tracer might work well.
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Re: capacitor leakage go/no-go test
Have you checked out videos on Utube from Mr. Carlsons channel. He does one of these?
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Show quoted text
Hi Pete & All
I, too, am interested in this and have been thinking about building a leakage tester.? I had one years ago, back in the days of valves, that used a 'magic eye' as the leakage detector, although I often suspected that test equipment might have been leakier than
the things it was testing!? I shall follow this with interest.
--
All the best
Richard M0RBF
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Re: capacitor leakage go/no-go test
Unless you want to repair early tube equipment you should hardly
need a leakage tester. If you do deal with early tube equipment
then replacing all paper capacitors with plastic film types is a
sensible start. A regular 20K/V meter on a voltage range will
indicate 0-50uA leakage and have series protection. Most bench
DMM's are 10M ohm Rin with a basic 200mV FSD.
If you put a suspect cap in series with a DVM and a power source
you can start on a suitable V range then switch to current if
needed. On a voltage range with 10Mohm input you are also seeing
0.1uA/Volt. Putting 1.1 Mohm across the terminals as a shunt gives
1uA/Volt, 100K gives 10uA/Volt. So I don't think a leakage tester
is very useful apart from mains leakage which is another matter.
What is FAR more useful is an ESR meter. Most electronic
equipment made in the last 20 years? fails because of
electrolytics loosing capacity through loosing water, often the
can ruptures or detaches. Many PC motherboards kill CPU's because
of cooked electrolytics. The ESR meter allow very fast testing of
electrolytics and the detection of failing parts before they do
extensive damage. Many CCFL's fail because their reservoir
capacitors fail, many wall warts fail for the same reason, the
result is pulsing the equipment at double line frequency which
will often cause a processor to be reset very rapidly.
ESR meters measure impedance with a low voltage but relatively
high current signal around 10-50KHz,? Testing is mostly in-place
i.e. mostly no de-soldering is needed, with a good tester it
should be possible to check a capacitor in a few seconds.
Regards, Alan G8LCO
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Re: capacitor leakage go/no-go test
On Wed, Nov 30, 2022 at 07:06 AM, Toby wrote:
Mr Carlson's Lab has published a design for a device for making this test that seems to work well (based on his videos).
?Mikek
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Re: capacitor leakage go/no-go test
Hi Pete & All
I, too, am interested in this and have been thinking about building a leakage tester.? I had one years ago, back in the days of valves, that used a 'magic eye' as the leakage detector, although I often suspected that test equipment might have been leakier than the things it was testing!? I shall follow this with interest.
--
All the best
Richard M0RBF
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Re: capacitor leakage go/no-go test
On 2022-11-29 9:29 p.m., saipan59 (Pete) wrote: I have various piles of old caps, many NOS, etc. I'm interested in doing a simple go/no-go type of test for leakage.
Have power supplies that can do 0 to 3kV DC.
Is it practical to put the cap in series with a microammeter (mechanical, to not risk damage to a DVM) and a current-limit resistor, then just dial up the voltage up to the rating of the cap (or beyond)?
One part of my question is: When (for example) a paper coupling cap goes leaky, just how leaky is it?
If a (for example) 20uA full-scale meter would not be sensitive enough, perhaps I set up a triode tube with a rather high-value grid R, and see if a leaky cap is able to change the bias. Mr Carlson's Lab has published a design for a device for making this test that seems to work well (based on his videos). --T Thanks for any comments!
Pete
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capacitor leakage go/no-go test
I have various piles of old caps, many NOS, etc. I'm interested in doing a simple go/no-go type of test for leakage.
Have power supplies that can do 0 to 3kV DC.
Is it practical to put the cap in series with a microammeter (mechanical, to not risk damage to a DVM) and a current-limit resistor, then just dial up the voltage up to the rating of the cap (or beyond)?
One part of my question is: When (for example) a paper coupling cap goes leaky, just how leaky is it?
If a (for example) 20uA full-scale meter would not be sensitive enough, perhaps I set up a triode tube with a rather high-value grid R, and see if a leaky cap is able to change the bias.
Thanks for any comments!
Pete
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Re: Sun DGA 1000 Gas Analyser
Thanks for the reply Paul. As you know I replied replied Via PM.
Thanks also Oliver for that info, I should have mentioned I'm in the UK.? Much appreciated all the same.
It looks like I may have found the problem after having removed the Controller board.? The track side is riddled with green corrosion from the leaking 3.6V Varta back up battery.? Little evidence on the component side but the Solder side is a different story. Looks like Grass in places. Many of the tiny Vias are black and blocked and some no doubt are open circuit.? Looks like I'll have to spend quite some time doing repairs before I can power it up again..
Denis
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Re: Two interesting projects
There were 'Top Octave Generator' ICs like the Mostek
MK50240Nthat were driven by a crystal timebase.
Yes, Pete,
It does. Accuracy!
Conn tried to develop a device for tuning musical instruments - could have been over 50 years ago. It used multivibrators as oscillators and a magic eye - 6E5, as I recall - for indicating when the sound picked up by the microphone matched that of the multivibrator. The idea was brilliant because the human eye can detect slow flicker far better than the ear. The multivibrator was a valve job that drifted as the device warmed up. So, you had to tune up quickly; it was really only good for single-note instruments like the brass and woodwind families. You could use it for the string families if you tuned one string and then relied on fretting and your ear to tune the other strings; however, I have seen fretted guitars whose fretting is way out, just by visual inspection. Fine tuning every string of a piano or harp was a PITA because of the drift. In those early days, I just tuned one note, A = 440 Hz, and then relied on mathematics, listening for the sharpness and flatness of the natural harmonics.
Then solid-state devices came on the market, whose accuracy was, in some cases, woeful. Some used multivibrators whose components aged in unpredictable ways and some divided down from a higher xtal frequency, like electronic watches.
Cheers, Brian, VK2GCE Brian Clarke BE, MBA, PhD, CPEng,? APEC Engineer, IntPE(Aus),?FIEAust MD, Clarke & Associates P/L
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Mon, 28 Nov 2022 16:41:09 +0000
Subject: Re: [Test Equipment Design & Construction] Two interesting projects
Does any of this musical discussion, interesting (to some) though it is, have anything to do with Test Equipment?design?
The SNR of the thread has drifted alarmingly.
Pete G4GJL?
Email sent using Optus Webmail
|
Re: Two interesting projects
Yes, Pete,
It does. Accuracy!
Conn tried to develop a device for tuning musical instruments - could have been over 50 years ago. It used multivibrators as oscillators and a magic eye - 6E5, as I recall - for indicating when the sound picked up by the microphone matched that of the multivibrator. The idea was brilliant because the human eye can detect slow flicker far better than the ear. The multivibrator was a valve job that drifted as the device warmed up. So, you had to tune up quickly; it was really only good for single-note instruments like the brass and woodwind families. You could use it for the string families if you tuned one string and then relied on fretting and your ear to tune the other strings; however, I have seen fretted guitars whose fretting is way out, just by visual inspection. Fine tuning every string of a piano or harp was a PITA because of the drift. In those early days, I just tuned one note, A = 440 Hz, and then relied on mathematics, listening for the sharpness and flatness of the natural harmonics.
Then solid-state devices came on the market, whose accuracy was, in some cases, woeful. Some used multivibrators whose components aged in unpredictable ways and some divided down from a higher xtal frequency, like electronic watches.
Cheers, Brian, VK2GCE Brian Clarke BE, MBA, PhD, CPEng,? APEC Engineer, IntPE(Aus),?FIEAust MD, Clarke & Associates P/L
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Mon, 28 Nov 2022 16:41:09 +0000
Subject: Re: [Test Equipment Design & Construction] Two interesting projects
Does any of this musical discussion, interesting (to some) though it is, have anything to do with Test Equipment?design?
The SNR of the thread has drifted alarmingly.
Pete G4GJL?
Email sent using Optus Webmail
|
Re: Sun DGA 1000 Gas Analyser
?? ?The 3 guys I know of that deal with older sun equipment? 2 I have found on Ebay. One known as "mnnorthwoods" I have
purchased a manual for a different Sun tester. The other is known as jas2fast, I have not dealt with him, although he
seems to have various parts.The 3rd is a fellow called Gary at http://timinglightfix.com/
?? ?ov
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Re: Two interesting projects
Does any of this musical discussion, interesting (to some) though it is, have anything to do with Test Equipment?design?
The SNR of the thread has drifted alarmingly.
Pete G4GJL
I enjoyed physics, actually minored in it, but I must have slept through that explanation, if it was covered.
?
Overwound guitar strings also go dull or ‘dead’ after a period of time. Though it’s more often oil and dead skin cells that collect in the overwound wire. Careful cleaning with a high quality organic solvent can extend the life of good guitar strings a long time.
?
My lab assistant played 5 string electric base in a jazz band and she’s take her strings off every 6 months of so, boil them in a soapy water solution, then plain water, bake dry and reinstall. She’d gotten 5 or 6 years out of the same set.
?
By moving your plucking fingers toward the fretboard, away from the soundhole in an acoustic guitar you get a softer more lute like sound at the expense of volume.
?
The “action” or string height above the fretboard is a concern. Lower action, closer to the fretboard, is easier to make notes but requires a more delicate touch, but, if the action is too high, then when you press the string down you change the tension enough to force the note sharp.
?
Deciding on a string height is delicate balancing act between skill, technique and style of music you like.
?
I paid a luthier to customize the action on my guitar and install an adjustable bridge. She also offered much needed advice on fingering and fretting technique and exercises to improve my technique..
?
I much prefer a zero fret over a standard nut. The intonation is more accurate if there are any open strings and the open strings sound 'cleaner.' I can't qualify "cleaner." I need to capture the audio and run it through a FFT program to see if there are any differences. I own two guitars, one with a traditional nut, the other with a .zero fret.
?
?
Then there is the sad reality that most guitar necks are slightly bowed.
This is an issue that has to be taken under consideration.
?
I play alone for my own enjoyment so being? a fraction of a hertz out of tune isn’t an issue. It’ nice to get lost in a difficult piece and the world goes away for a time. Our daughter calls it “Zenning out.”
?
The friend of a friend has an Ebow:
It’d almost be worthwhile to switch to an electric guitar for the nice effect the Ebow gives. An Ebow will work on an acoustic guitar but the ‘touch’ required is beyond my skill set. The sound is very soft, magical, maybe a cross between a harp and violin.
?
I ran this past our daughter, classical trained pianist, “Tremolo traditionally referred to a slow rhythmic change in volume and vibrato to a slow rhythmic change in pitch. Though today the terms are often used interchangeably.”
?
I finish “My Lady Greensleeves with vibrato on “A” on the “G” string, slowing the vibrato as the note dies away.
?
I’ve never played for anyone but family, the luthier so she could made some judgments on the best action height for me and my EE friend as he taught me his version of House of the Rising Sun. He plays what he calls “broken arpeggios” and does some odd stuff to the timing that even our daughter can’t quite pinpoint. He crams 6 notes where 4 goes but it isn’t forced.
?
Like me he’s self taught and does a lot of things “wrong,” but some of his interpretations are very nice.
?
His interpretation of Classical Gas is amazing. His wife plays flute their version of Nights in White Satin is haunting, she extends the flute part and plays a nice counter point. String instruments make sense, shorter strings, or thinner strings under more tension, produce a higher note. A flute is insane. My friend's wife played the scale and her fingers were all over the place. I'm certain there is solid math underlying but it is far from clear. I do get the "push air across a tube with twice the velocity?and produce a tone 1 octave higher."
?
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Re: PCB making software, What do you use?
On Wed, Nov 23, 2022 at 08:12 AM, Forrest Erickson wrote:
I hang out at a KiCad Facebook group where beginners ask for help coming up to speed. I composed this:
?
The three best KiCad tutorials I have found to date 20221121.
?Thank you for posting that information. (not that I need to spend more time watching Youtube!) :-) ????????????????????? Mikek
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Re: Two interesting projects
Hello Jeff,?
In the pendulum frequency formula, the factor ‘k’ includes the
force of gravity. For a stretched string, the ‘k factor becomes a function of
the string tension. Of course, it’s not as simple as that because stringed
instruments – harp, guitar, piano, violin – anchor the stretched string at both
ends. At the fundamental frequency, the string is one half-wavelength long,
with nodes at each end. Natural strings, those with uniform distribution of mass
per unit length, will therefore only produce odd harmonics – 3rd, 5th,
7th … Violinists can choose to emphasise or attenuate specific
harmonics by choosing exactly where to bow or pluck. Hence, the ‘sweetness’ of
the violin’s sound depends almost entirely on the violinist’s skill. You can do
the same with your guitar.???
In order to suppress that most disharmonious 7th
harmonic on the piano, the hammer strikes at the node of the 7th
harmonic. Re-tuning a vintage piano, that is, one designed for A = 420 Hz, to
bring it up to modern standard pitch of A = 440 Hz, the additional tension on
the harp will shorten the harp and automatically shift the hammer strike point
away from the node of the 7th harmonic. The tension on the harp is measured
in tonnes – several! The sound board to which the harp is attached may well
crack under such insult. Good piano tuners often refuse to raise the pitch of
older pianos.?
The formula for the fundamental frequency, f1, of
a string anchored at both ends is:?
f1 = ? √(T
/ mL)
where:
T = string tension
m = string mass
L = string length?
Now you can see why I referred to the pendulum formula – I was
using a mathematician’s shorthand.?
For over-wound strings, the mass per unit length is not uniform,
and hence the harmonics are not exactly 3rd, 5th and so
on. The amount and style of over-winding gives each piano manufacturer’s design
its specific ‘voice’. Over time, the repeated striking of the over-wound
strings results in relaxation of the over-winding pattern, and the note sounds
increasingly dull. A cunning piano tuner will then release the tension on the
dull string, rotate the string at the end furthest from the hammer, re-tension
and re-tune to get some of the previous harmonic richness back; this method is
cheaper than getting a new string wound.?
For string basses, some players like to use over-wound strings
because of the smaller tension on the tuning peg. A further benefit is a
‘richer’ sound from such over-wound strings – the string excites more air.
Purists will still prefer non-over-wound strings. You know that over-wound
strings are available for tenor and bass guitars.?
More grist for your mental mill.?
Now that you know about the equally-tempered scale, you know
that G should actually be 199.59977 Hz. So, if your tuning fork is exactly
196.0000 Hz, and if you could tune accurately to that tuning fork, fellow
musicians whose instruments had been fine tuned to the equally-tempered scale
would sound about 0.4 Hz flatter than you. This would be experienced as a beat
approximately every 2.5 seconds. Unless you use an electronic device to stretch
tone level over several seconds (eg, a sustain pedal), neither you nor your
fellow musos would know. However, if you play a G a couple of octaves higher,
the 0.982 Hz beat will be more noticeable over a shorter time period, ie, less
than a second. Some string players attempt to get around this problem by
rocking the ball of their finger over the string on the finger board, or fret
board, to induce a frequency tremolo.?
When I tune my piano, I use an electronic tuning fork that I
have compared, using my oscilloscope, with the tones from WWV. Even when I get
within 1 cent, I still listen for beats for 13 seconds. I don’t look forward to
tuning my piano because it takes me several hours. My piano invariably goes
flat. I pull up the middle octave of 12 notes, the harp compresses, all the
adjacent notes go flat. So, I then do the octaves above and below the middle
octave, and then retune that middle octave. And so on, leap-frogging back and
forth.?
Cheers, Brian.?
From:
[email protected]
[mailto:[email protected]] On Behalf Of Jeff
Green
Sent: Sunday, 27 November 2022 1:57 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Two interesting
projects
?
On Fri, Nov 25, 2022 at 11:50 PM, Brian wrote:
Thank you, you answered
questions I never knew I had.
I learned that formula as: ?f?= (1/(2π))√(k/m)
as it applies to pendulums and never considered how it would apply to a musical
string.
?
The
math for a double body pendulum is .... interesting.?
?
One thing
the equation leaves out is tension. As I think I said, I play guitar (with
perhaps more energy then skill.) So I am very familiar with tuning.
?
I have
a 196Hz tuning fork, open “G”, that I used until my EE friend showed me a $25(US)
Deltalabs CT-30 clamp on tuner.
?
Guitarists
with ‘the touch’ can produce harmonics on the 3rd and 6th
fret. A good way to check proper fret placement is to compare the harmonic touching
lightly above 12th fret with the note produced on the 12th
fret.
?
The bridge
on most acoustic guitars is slanted so the higher strings have a short overall
length to allow for the difference in wound versus straight strings.
?
I thought
all the strings in a piano had multiple strings. Our daughter once told me “Daddy I love you but you are not to open the lid
on my piano!”
?
For some
reason she thought I might play with the innards. I’ve been foolish more times
in my life then I like to admit, but even I’m not silly enough to mess with the
inside of a delicate piece of equipment.
?
I’ve
played with a Brazilian fretless guitar once and once was enough. One would need
perfect pitch to find the note and thinking of making chords on a fretless guitar
make me want to sob.?
?
If you
want to cause minds to melt, go into “transposing instruments.” It is easy for
guitar, the music is written one octave higher then it’s played.
?
Or delve
into the never ending war over “Is 440Hz right?”
?
The Baroque
crowd goes for an “A” of 415Hz and considers the rest of us to be heretics.
?
My EE
friend sent me these links.
?
We humans
can find the oddest things to fight over.
?
I can’t
wait to ask our daughter about the Rhodes Piano, I wonder if she’s ever used
one.
She says
the Clavinova digital piano is almost a real piano. The feel of the keyboard
comes very close to the feel of a real piano.
?
What I find odd is the Treaty of Versailles
has a codicil that sets concert pitch:
“Article 282
Section 22 of the Treaty of Versailles: "Convention of November 16 and 19,
1885, regarding the establishment of a concert pitch."?
?
A friend tracked down a PNG of the
entire treaty and I have a PNG copy of “Article 282 Section 22.”?I can place the PNG in the files section but it isn’t
informative because if refers to a previous international congress. My friend
is trying to track down a copy.
?
This offers one explanation for A=440Hz:
"The B.B.C.
tuning-note is derived from an oscillator controlled by a piezo-electric
crystal that vibrates with a frequency of one million Hz. This is reduced to a
frequency of 1,000 Hz by electronic dividers; it is then multiplied eleven
times and divided by twenty-five, so producing the required frequency of 440
Hz. As 439 Hz is a prime number a frequency of 439 Hz could not be broadcast by
such means as this."
Easy peasy, I bet that occupied several equipment racks.
I might have divided down to 10Hz, square it, extract and amplify the 11
harmonic, 110Hz, then double to 220 and double again to 440.
Brian Clarke BE, MBA, PhD, CPEng,? APEC Engineer, IntPE(Aus),?FIEAust MD, Clarke & Associates P/L
Email sent using Optus Webmail
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Re: Two interesting projects
On Sat, Nov 26, 2022 at 06:57 AM, Jeff Green wrote:
I have a 196Hz tuning fork, open “G”, that I used until my EE friend showed me a $25(US) Deltalabs CT-30 clamp on tuner.
I have a Pickboy tuner, manufactured by Seiko/Epson (I'm going from memory, I don't have the tuner handy) that I bought over 30 years ago.? At the time it was, as far as I know, the only electronic guitar tuner worth buying, at least of the "consumer" devices.? I had an A 440 fork, which I checked against an expensive and recently calibrated HP frequency counter.? My fork was dead on 440 Hz.? I? went to every music store in the greater Raleigh, NC area and checked every electronic tuner they had.? Any tuner that said my fork was off pitch was rejected, and if they had more than one tuner of the same model in stock, if any tuner of that model said my fork was off, that model was rejected.? I had gotten so sick of going to jam sessions and such where no two instruments were tuned to the same pitch, and so many of them weren't even in tune with themselves, that I decided I had to find something that actually worked.? And the arguments at jam sessions were ridiculous: "My instrument is right, because I am tuned to my electronic tuner."? Some tuners had a selector switch to select the note to be tuned, and they might be correct (or close to it) on one note, but not on others.? Some tuners varied unacceptably with ambient temperature, while others varied with battery voltage.? I have done a lot of electronic design, and many of the tuners I encountered over the years were so bad that if I were asked to design a tuner that worked so poorly, I'm not sure exactly how I would do it, and of course I would turn the assignment down.
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Re: Sun DGA 1000 Gas Analyser
Snap,
I too have an old Sun Gas Analyser tucked away.? It sounds like it
is even more ancient than yours. I had it calibrated a couple of
decades ago. It is supposed to be an instrument grade device and
very accurate when in spec.? I have no further use for it and am
in South Shropshire.
Paul G8AQA
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Show quoted text
Hi
I believe this post does come under the requirements of
Professional Test Equipment design.
I've had this elderly Sun Gas Analyser?unused and?gathering dust for quite
a while.?
After switching on the unit, the display indicates it's
running an Initialisation routine that stops after some 54 seconds
indicating a ROM failure.
I've verified that the four 1Mbit EPROMS have checksums which
annoyingly agree with the labels on the devices.? There are also 3
programmable 0.3" DIP devices which I can't check yet without
making some sort of adaptor for my Programmer.? What they do is
anybody's guess.
It's a pretty complicated
beast which clearly is partly alive. A long shot I know, but
does anyone have any circuit or other info on this unit. Any
help would be greatly appreciated as I'll be in need of it soon
for another home construction project.
I posted this on the Vintage Radio Forum a few days ago but
so far nothing has been of help.
Thanks
Denis?
|
Sun DGA 1000 Gas Analyser
Hi
I believe this post does come under the requirements of Professional Test Equipment design.
I've had this elderly Sun Gas Analyser?unused and?gathering dust for quite a while.?
After switching on the unit, the display indicates it's running an Initialisation routine that stops after some 54 seconds indicating a ROM failure.
I've verified that the four 1Mbit EPROMS have checksums which annoyingly agree with the labels on the devices.? There are also 3 programmable 0.3" DIP devices which I can't check yet without making some sort of adaptor for my Programmer.? What they do is anybody's guess.
It's a pretty complicated beast which clearly is partly alive. A long shot I know, but does anyone have any circuit or other info on this unit. Any help would be greatly appreciated as I'll be in need of it soon for another home construction project.
I posted this on the Vintage Radio Forum a few days ago but so far nothing has been of help.
Thanks
Denis?
|
Re: Two interesting projects
I have 2 Singer-Gertsch service monitors.?
An FM-10 and a FM-10C.? No spectrum analyzer but everything else is as you say.
?
Paul, W8AEF
?
toggle quoted message
Show quoted text
From: [email protected]
[mailto:[email protected]]
On Behalf Of Jeff Green
Sent: Saturday, November 26, 2022
4:52 PM
To: [email protected]
Subject: Re: [Test Equipment
Design & Construction] Two interesting projects
?
Obi
Wan, you have increased my knowledge.
?
I
started this thread because I thought 2 of Rod Elliot’s projects would be of
interest to members herein.
?
My EE
friend described a RF test set that analog two-way radio stations used that did
many of the tests of Mr. Elliot’s PC based audio test system.
You
could verify frequency, deviation, use SINADD to check signal to noise and
align RF front ends, check the receive audio for power and I think he said THD
and an RF spectrum analyzer. Oddly he said it was manufactured by Singer.
?
I
thought Mr. Elliot’s design might prompt others into considering their own.
?
The
“test patch bay” looks interesting in its own right, add outputs for frequency
counter, a dedicated and disposable SDR for spectrum analyzer, either a very
stable RF generator with calibrated outputs or something like the Elecraft XG-1
1uV/50uV signal source.
Sort
of a one stop “box” that would allow quick and repeatable testing without
having to look
for that missing patch cord.
?
?
While
a GPS DO costs less then $200(us) and offers amazing frequency accuracy with
low jitter, my EE friend showed me a neat if obsolete “different way” to get
sub-hertz accuracy.
?
|
Re: Two interesting projects
On Wed, Nov 23, 2022 at 03:58 PM, Jeff Green wrote:
Another snake oil sale pitch is special purpose power cables. The AC mains passes through so many miles of transmission line, transformers, etc, that magical thinking a 6 foot special power cord will be of any help is silly.
Love it. I remember going into a consumer electronics store needing a power strip and sales person insisting some almost $100 dollar power strip was what I absolutely needed. Based on the amazing power cord technology.? I bough an inexpensive power strip a while back with $50,000 damage insurance. For the insurance to be valid, you could not plug the equipment and power strip into a wall plug farther than 10 feet from the power panel. Could not have any other extension cords or power strips plugged into the same wall plug or the power strip. And on and on. The truly sad thing is these marketing/"business" people that pull this magical thinking out of their behinds, also find their way into decision making positions in companies that produce things that really do need to conform to the laws of physics and nature.? Sad when they are fleecing consumers but otherwise causing no harm. But, horrible when they find their way into fields such as medicine, aeronautics, and computer fields like artificial intelligence.? Tom, wb6b
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Re: Two interesting projects
Jeff
1KHz = 2^3 x 5^3 Hz and
440Hz = 2^3 x 5 x 11 Hz
so the difference is? 5^2 and 11.
This gives rise to x11 then 1/25 to produce 440Hz. That is all you need.
The multiplication by 11 from 1 KHz square wave to 11 KHz is very much better than trying to multiply 10Hz to 110Hz, an 11 KHz tuned circuit of good Q is much easier, cheaper and smaller than a 110 Hz tuned circuit. The division by 25 is very simple, either two locked multivibrators ( two double triodes or two blocking oscillator dividers and one double triode to do 1/5 and 1/5 to get down to 1/25 and 440 Hz.
You would loose your bet, two or three? double triodes would complete the job and should be quite stable. A very good crystal oscillator , oven and divider chain AND the 1K to 440Hz? synth would easily go into a single thin rack panel or a small box in the 1950's.
There is something much more interesting than 440Hz about musical notes. A good enough equal temperament scale can be produced by dividing a frequency around 2 MHz by integers to produce top notes then dividing by octaves. The sequence:-
239? 253? 268? 284* 301? 319? 338? 358? 379? 402? 426? 451 gives a workable set of approximations to the ratio of 1.059463094 between adjacent notes.?? 284 is for A,? the exact drive frequency is 1999.360 Hz for 440 Hz but 2 MHz is close enough.? 12 different dividers were contained in one I.C.? and replaced 11 L-C oscillators in electronic organs in the 1970's. The idea is earlier, Hammond organs used gears to multiply up and down from a synchronous motor driven by mains frequency. Gears are more versatile than dividers, machinists have used some clever gear combination for over 200 years to cut specific threads however the last Hammond did use top octave dividers instead of gears.
But distant Musical History now but very little to do with Test Equipment apart from the frequency synthesis aspect.
Regards, Alan G8LCO
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Richard
saipan59 (Pete)
Michael A. Terrell
Brian
Pete_G4GJL
Jim Allyn - N7JA