Scope, Function/signal genereator, probe questions.

[Haze13]

Today I bought my first scope! It's a Leader 1021, 2-CH, 20 MHz - Analog. Standard analog 20MHz scope, nothing fancy, but in a working condition.
So my first question is goes like this... I have a probe for this scope and a BNC cable with 2 crocodiles, and some how this cheap BNC cable does not react to any movement of the cable, but the Probe is always "creates some noise" and it's very hard to understand to is it a PCB or just old/cracked probe. Is there any good Probe on ePay or other store that is worth buying or should I just stay with BNC?

And the second:
For calibrating modulation effects I need 200Hz sine wave 3dB source. Will it be enough to buy china made small kits DDS Function Generators or (1-2 MHz) or buying old analog FG will be a better option.
I'm not running any business but I do Learn at Institute of technology, so I do need to learn how to use this stuff, because Lab classes is not enough I think.

[slacker]

Probably the easiest and cheapest way to generate test tones is install Audacity on your computer, this can generate a range of signals, you can also save these and use a cheap mp3 player or an old mobile as a more portable solution. For what we do a function gen is only necessary for signals outside of audio ranges.

Sorry don't know about the probes, maybe borrow some different ones if you can and see if they do the same thing.

[GibsonGM]

You can get cheap probes on Ebay for about $20 (US) !    They will work fine for audio frequency work that we do.  The very nice probes are more for high frequency use (high MHz, GHz....).  Just search for "oscilloscope probes".

Are you SURE the scope is working?  If so, a simple 2-wire test will show you SOME kind of wave on it, just very noisy and not good.   If you know the scope is good, then I would buy the above-mentioned probes.

I use an old computer from 2001 for a function generator; it is a 766 MHz.  You can find one for VERY low cost.   There is a free program called "Visual Analyser" that is a PC O-scope, but also can generate signals in the audio range (range of sound card....50Hz to 22kHz, approx.).   VERY useful.     You can also use the program to sweep frequencies and the like, as well as to generate sine, square, sawtooth, triangle waves, and noise.   I run a line out of the computer to a simple opamp amplifier so I can have a few volts to play with.   Much less expensive than a real signal generator!

[Kipper4]

I have the same scope. That I bought recently.
On the bottom row of knobs (position) between the BNC connectors there is a little hook type thing. Which is the scopes internal signal generator.
Connect the positive terminal of the probe to that and adjust the time division and volts division knobs until you see a broken line. Which should indicate the presence of the internal square wave.
The vertical lines of the wave will likely be almost invisible. This will indicate the scope is functioning.

[Haze13]

Thanks for the replies!
0.5p-p V, 1KHz test - That's the first thing I've done to this scope, and yes with the probe the wave was very strange... At first the square wave was rounded, like there was a capacitor... I moved the clip that goes to the ground, moved the cable and than it was Ok. Normal square wave. With BNC there was no problem at all!
Looked at the LFO of the chorus that I working on, and same again...  With BNC it look way much better that with the prob. Problem is that I use very small resistors  (1/8 watt) and there is no much place for the  crocodile, but even rudely connected DMM probe to the crocodile of the BNC cable gave better result than with the Probe!

Kipper4, if you have the same scope, it's possible that we have same scope from the same year, more or less. I wanted to know if I need to do some maintenance like changing filter caps or some thing...  I had a tube amp (carvin XT100b - combo) and it was from early 90's and filter caps needed to be changed or I could burn power transformer.  This scope is from the same years, so it makes me to think that I can run in to the same problem...

[Seljer]

That square wave generator on the front of the scope is used to calibrate probes. Many of them will have a little adjustable screw for trim capacitor that let's you sort out the probe's frequency compensation. You observe the generated square wave and adjust until you get the 'nicest' waveform (not too slow of a response, no overshoot or ringing either).

Get some probes with the little spring loaded hooks, they have no trouble hooking up most through hole components.

[anotherjim]

+1 Seljer

If it's a x10 probe there is a capacitor!
But, it's a trimmer capacitor fitted at the scope end - you should find a hole with a screw adjust visible. Most probes come with a tool for that, a phosphor-bronze tang in a small plastic handle.
Adjust it while viewing the scope test signal. You should be able to get a nice square wave.
This is "probe calibration" - all scopes and x10 probes should have it.

[Haze13]

Yes, I know... The problem is that I couldn't find that point, and when I move, touch, hold, bending the cable of the probe the picture on the screen is changing...  Some times it's shoes a good square signal, some times it's rounded, like triangle wave but rounded on to sides. I think it's just a faulty probe.

[Seljer]

Check the continuity on the ground/shield of the probe with a multimeter, sounds like it's theres a break in it.

[GibsonGM]

Check the continuity on the ground/shield of the probe with a multimeter, sounds like it's theres a break in it.

Yes, but also if you just move it (not connected to circuit) then expect to see it get all weird.   Even if it's IN circuit, if you go bending the probe wires out of the way etc., the waveform can be expected to move somewhat. There are capacitances all over the place in the world     I don't mean CONSTANTLY, just a bit.  If I were having real difficulty, I'd just get some Ebay cheapos that will work fine!    Esp. with the above-mentioned clips, which take your hands out of the equation.

I got these for my 1982 Tektronix, and they work VERY well for what we're doing (no microwave comms. going on, lol).  If your scope is from the 90s I'd think they'll be fine also (BNC).    BTW, your caps may or may not be 'old'...mine are fine, even from the early 80s....

http://www.ebay.com/itm/Two-x1-x10-100MHZ-Oscilloscope-clip-probes-HP-Tektronix-/220375454020?pt=LH_DefaultDomain_0&hash=item334f669144

[Haze13]

I see these probes every where in Ebay... You say that they are fine, so I guess I'll try them.
Strange that my BNC does not change the picture on the scope, and no matter how ward I'll bend it, and this is really cheap BNC cable

[anotherjim]

Ok, a properly compensated scope probe should be stable. From what you say, yours is faulty.

You do get what you pay for, so I wouldn't go for the very cheapest.

What I find worse with cheap probes are the clip on spring hook tops. They either fly off on their own or make poor contact with the real probe tip.

[duck_arse]

you can test yr probes by clipping the probe-end ground wire to the probe tip. wiggle about then, see what on the screen. it should be steady flat.

my probes drive me crazy, combined with dying breadboard contacts. the earth clips are dirty, so make noisy contact, and the weight of the probe on the components makes the bb contacts noisy. so I mainly use a ground wire from the cro f/panel to the bb.

[Kipper4]

These are the probes I bought off ebay for six of our English pounds P+P paid

http://www.ebay.co.uk/itm/321013404335?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_3042wt_958


that would be around 10 Dollarees US

I also bought a bunch of solder hook probes off the bay for a song. So I can make DMM probes for debugging and flexability

I have no intention of recapping my scope. I'm a strictly 9v kind of guy. If its more than a tingle on the tongue, I'm not qaulified.

I'm hoping my scope will last many more years. I believe its an 80s or 90s model. I cant image it would have been left on for prolonged periods so I figure there should be plenty of life left in the caps etc

[Haze13]

Thanks for the tips:)

Kipper4, and I am some thing opposite to you:) 9 volts is never enough for me. Worked on some Tube Amps and Build one (JCM800 2204)...
So I think there shouldn't be any problem for me replacing them, just don't know if I should. Hope not in the near future!

[PRR]

> Worked on some Tube Amps

Note that modern probes use low-Voltage capacitors. I used to blow-up 400V probes regularly, and today's probes may be 100V.

10Meg and 100K make a 100:1 probe that will handle 600V without instant death (use a 1/2W part for the 10Meg) and not need compensation to 20KHz (keep coax under a few feet).

[Haze13]

Thanks PRR.
Scope wasn't needed for tube amps that I worked on. Problems were obvious and the build was successful from the first try Except the radio interference.

[GibsonGM]

> Worked on some Tube Amps

Note that modern probes use low-Voltage capacitors. I used to blow-up 400V probes regularly, and today's probes may be 100V.

10Meg and 100K make a 100:1 probe that will handle 600V without instant death (use a 1/2W part for the 10Meg) and not need compensation to 20KHz (keep coax under a few feet).

Great point...read the specs on your probes, and REMEMBER them before you jam them into your B+, LOL!   If in doubt, make a divider as PRR suggested.

Those probes Kipper showed will be fine for what we do, Haze - the caveat being, as mentioned, that if you aren't careful with them and pull on them, etc., they'll have a shorter live than quality ones.  Unfortunately, 'quality' mostly means very expensive.       I'd rather get new probes every 5 yrs. than fork out that kind of money!

I have the same type, essentially, and they are taking my abuse very well.     

[Haze13]

Thanks for the advises, but the last time when I worked on "live" tube amp was a while ago, and some how I don't want to see how B+ Looks Like  
Installed the Audacity program! Works very well, now I see what choruses do and how analog delays behave...  And! A hear 20KHz!!!
But Only through good headphones (shure SRH440)...  Forgot about the program and was working while it was running on max vol through netbook speakers. I didn't pay any attention to it