Just got an Oscilloscope!

[craigmillard]

Hi Guys,

I have just been given a very old OScope by a college at work its a Telequipment D67.

It looks like its all working as can calibrate it according to the manual and it is showing a sine wave from a 12v power pack when probed..

Im looking to use it for valve amp diagnostics, determining noise on power lines etc, but am unsure where to start!!!

Any good guides or advice??

I think it can handle DC inputs upto 50V (Volts/Div goes upto 50v) on a 1x probe but also have a x10 probe...

Cheers

[armdnrdy]

The first thing that you should do is see if you can find the user manual online. (If you don't have it)

The user manual will be very helpful.

There are online tutorials on how to use an oscilloscope as well.

Edit:
Too much coffee this morning! 
I just reread your post about calibration according to the manual. 

[GibsonGM]

Youtube is your friend!  Look up "Oscilloscope tutorial", there are TONS. Watch the one about how NOT to blow up your scope, it is rather important )

Find an old 3 to 9VAC transformer and make an OCTOPUS!  Plans from any search engine...it can help you diagnose circuit boards.   Check out how to make Lissajous figures, they can be neat.   

Your using a 12V sine wave showed good instinct - keep it out of the power outlet, and watch out for setting it on voltage ranges that would be more than a couple of times the actual voltage (read your manual, it will be more specific) Ex: you'd never want it set on .1V if you were about to look at a 50V signal!   That will blow your input board (probably the most common fault found in scopes).    Gotta use your noggin....find out what "X10" means re. your probes...esp. for tube work...start small, don't go into HT until you know you won't kill the thing...

And mostly have fun!  Remember, the goal is to show just a couple of cycles of what you're looking at, nice and steady so you can measure (read up on 'triggering').    )

[psychedelicfish]

I think it can handle DC inputs upto 50V (Volts/Div goes upto 50v) on a 1x probe but also have a x10 probe...

The Volts/Div control changes how many volts per division on the screen, so at the 50 Volts/Div setting you'd need 50 volts to get the trace to hit the first horizontal line. Your oscilloscope could probably handle something more like 300V on that setting, but you should check what the manual says.

[GibsonGM]

Yeah.   I think my Tektronix manual (from 1982) says it can handle about 5x the input voltage.....so set at 50V, you could theoretically input 250V before there's an "issue".  Just something to bear in mind, that *any input you want* is off the table!     Trying 20V at 5mV settings - that could be messy!!    Your estimate of 300V being safe on 50 is a good rule of thumb.

When I got this scope off Ebay, I got it cheap as one channel didn't work.  A diode had blown on the input board, due to over-voltage, which is why I mentioned this. Luckily I could use the GOOD board to compare voltages, track it down and bam - easy fix.   

[PRR]

Standard 10X probes will NOT survive 500 Volts (no matter what the math says).

Modern low-cost ones may not be good past 100V. And may not be rebuildable. So beware.

For poking plates and B+ in tube amps, a 1Meg+10K 100:1 divider is handy. It does load the circuit some, and isn't flat to MHz, but you can see pretty-much what is happening on HV nodes without damage.

[GibsonGM]

Standard 10X probes will NOT survive 500 Volts (no matter what the math says).

Modern low-cost ones may not be good past 100V. And may not be rebuildable. So beware.

For poking plates and B+ in tube amps, a 1Meg+10K 100:1 divider is handy. It does load the circuit some, and isn't flat to MHz, but you can see pretty-much what is happening on HV nodes without damage.

Very sensible advice, Paul.     Before anyone goes into a tube circuit with a scope, I'd STRONGLY suggest they read up on how to do it right.  Can't just jump in and expect to skate over the effects you encounter up there, such as pierced insulation (is that what you're alluding to?). 
The beauty of the stompbox world is that we have so MANY low voltage circuits to mess with and become comfortable with before move up...that experience is invaluable when you enter the 'real world' of HT.

I've had much good luck using the 1M/10K....and also by being VERY SURE of where I am in the circuit, and constraining my 'investigations' to the regions behind coupling caps and the like  ;o)   Also by metering first to establish some test points, knowing what voltages are present before diving in.