trick to detecting clock?

A crystal earpiece, assuming voltages not more than 50 volt. A much underestimated piece of diagnostic test gear.

-- General electronic repairs, most things repaired, other than TVs and PCs

Diverse Devices, Southampton, England

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AC or DC voltmeter.

JF

With a multimeter that measures frequency.

Gareth.

You can use your computer's sound card. You can add a voltage divider to insure the sound card Line input is getting less than about

3 Vpp, if you want to make sure you don't clip its input. (The input can handle 5V without damage, but the wave will be clipped.) If you want to avoid loading the clock output with the sound card input (which can be in the 2K to 47K range), you can use big resistors for the divider. Don't worry about dividing it down too low... the sound card has 16 bits of resolution, so you'll be able to see sub-millivolts easily.

SHAMELESS PLUG: You can try my Daqarta software for free. It has calibration options so you can use it as a real scope (as well as spectrum analyzer, frequency counter, voltmeter, sound level meter, signal generator, etc, etc). If you decide not to buy (US$29.00) after the trial expires, the inputs stop working but the signal generator keeps working FREE forever, along with file analysis, etc.

I'll be glad to answer any questions.

Best regards,

Bob Masta DAQARTA v4.00 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

"j snipped-for-privacy@hotmail.com" wrote in news:ce59ac53-6740- snipped-for-privacy@s50g2000hsb.googlegroups.com:

With a few ICs and LEDs you can build a logic probe with pulse detection.

has several interesting circuits, easy to build.

and for a 'delux' device

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bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

bz+ser@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

Might I point out that an oscilloscope _is_ an "ordinary instrument"? At least, in my sense of the word "ordinary" -- it's ordinarily found in any electronics shop.

I work at Microsoft Hardware, and there has been a total switchover to multi-color LCD 'scopes. The cheaper ones are not _horribly_ expensive.

The obvious choice, as Mr Cook says, is a crystal earpiece.

With one of those, the OP won't even need to make 2 connections; just touching the tip of the jack plug on the conductor that's oscillating at a few kHz and a few volts will be enough to make it faintly audible with careful listening.

Martin

One of the most useful bit of kit in my toolbox is a device I made myself some 35 or so years ago. It`s a crystal earpiece with one wire terminated in a croc clip and the other in a probe made from an old ballpoint pen and a brass nail, there`s a capacitor in series to provide DC blocking. With this simple device I can trace audio through a circuit- from the output of a crystal pick-up to several hundreds watts, I can detect digital pulses, hear hum on a DC supply, etc. etc.

Ron(UK)

Buy a meter with freq. range. A lot of them are equipped with that. Mine(78Euro Extech)has Farad/Hertz/Farenheit/Celcius as bonus ranges, temp is done with a termocouple.

What a fascinating collection of notes you've kept on repairs you've carried out and published on your web site!

Thank you for that,

Chris

frequency counter?

"

On Sat, 14 Jun 2008 03:15:26 -0700 (PDT), "j snipped-for-privacy@hotmail.com" put finger to keyboard and composed:

If you are asking this question because you need to detect whether the clock is oscillating, rather than trying to measure its frequency, then find a buffered logic gate where the clock should be present and measure the voltage there. If the clock is oscillating, then you should measure a DC voltage equivalent to half the supply rail. Depending on the frequency response of your multimeter, the voltage on the AC range may be 0, so that won't be a good guide. If the clock is dead, then the gate will be sitting on 0V or close to the positive supply rail. Of course I'm assuming that the clock is a 50:50 square wave. BTW, you probably won't get any sensible result measuring the voltage at, or near, the crystal.

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.

I must do the same sometime. I've always picked up the standard earpiece and a pair of croc-leads and a needle point rather than making a purpose built tool. Adding in a HV cap if monitoring for noisy HT lines. A scope would not show any more info in that situation and avoids possibility of connecting scope up, in DC mode, set on 1mV/cm or HT pulse transmitted through internal cap of scope, on a low range, and out goes dual gate FET or whatever.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

At home I have an old analog scope with "Y" output, onto which I connected a simple amp+speaker.

The ticks / hums / squieks out of the speaker are extremely revealing about what is measured; most of the time I do not need to look at the screen at all.

In a cpu setup, one can even hear the software "run" on an adress line (reoccurring sound patterns), and actually hear subroutines and such.

At the office, the sophisticated DSO's no longer have this very useful option..

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 - René

Audio monitoring of program execution was standard practice on large computers for decades and for me is a sadly missed diagnostic of an often more useful nature than flow graphs and trace dumps. Using an AM or FM radio near programmed logic can sometimes provide similar functionality.

Michael

Then there was the demo program supplied (on cassette tape, natch) by The Digital Group for their Z80 systems, which "played" the Star Spangled Banner all over the AM band to a nearby radio while ASCII-arting a flag-like object on its 16x64 display. Way cool ...

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Rich Webb     Norfolk, VA