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Oscilloscrope noobie questions : BK Precision 15MHz Oscilloscope Model 1472C

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offensive_Jerk

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So I bought this filthy BK Precision 15MHz Oscilloscope Model 1472C at a garage sale for $1. It didn't come with any probes.

I don't know how to use one, but for $1 I'll attempt to learn.

Anyway, I brought it home, and plugged it in and turned it on. The LED lit up so it's got some power at least. I messed with the switches but nothing on the display came up except I could get a little line on the screen from time to time. Also turning it off makes a line display on the screen, so I think the screen works.

Question 1: Is there anyway to test this thing without probes to at least see if it works enough to get probes for it?
Question 2: Doing a quick search for probes, I don't know what to get. I see some rated for 200mhz, but the oscilloscope is 15mhz, does that matter? What probes do I need?

It looks like this:

1-f008116145.jpg
 
1.) Turn it on and make sure you get a green dot or line or something. Play with the focus and position settings to see if you get anything. If so that's a good start.

2.) Probes rated for a higher frequency shouldn't have any real effect on anything. Any generic BNC connector probes should work fine, even the cheap ebay ones. For learning purposes fancy stuff isn't what I would grab - even I'm using a cheap probe on my Tektronix TDS684B which was once pretty much their top of the line model and it works well enough and is a lot cheaper than a real Tek probe.

Congrats on the $1 score though. The old 'scopes are pretty cool and a lot simper to use than a lot of the modern digital ones. My Heathkit IO-10 is a lot less intimidating than the Tek for sure.
 
So there should be something on the screen when nothing else is hooked up? I'll have to play more with it later and see if I can get something on screen.
 
Pull the knob labeled "LEVEL Pull Auto" in the "TRIGGERING" section. That should make the scope sweep more or less continuously even if there is no input signal. This should give you a horizontal line that you can move with the horizontal and vertical POSITION knobs.

There appears to be a CAL output in the upper right corner of the panel. This should output a square wave. If you set the inputs to DC coupling, and select channel A then you should be able to get something displayed if you take a small piece of wire (e.g. a scrap of 24 AWG from a butchered network cable) and connect the CAL output to the center of the A input BNC. You might have to play with the attenuator (VOLTS/CM) and SWEEP to get it to work. Some settings may work much better than others due to dirt, age, etc. It is common for a scope of this age to need its controls cleaned even if all internal circuits are in good shape. Good luck.

The cheap ebay 100MHz probes are plenty good enough to get started. There's a listing for $8.99 with "free shipping" from a US vendor right now. They will come with the probe accessories that you might not get with used probes (e.g. "witch hat" clips, ground leads, colored identifying rings, etc).
 
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You need to play with the two knobs labeled 'Position'. You should see two *continuous* traces, with some noise on them. You should see no cuts or blanks, just two horizontal traces.
 
If the thing was filthy (sitting in a basement or garage), there's likely some corrosion on the switch contacts and/or dirt in the pots. Get an aerosol can of contact cleaner (you usually can find something in the auto section of most big-box stores), open the case up, spray some on the switch contacts and rotate the switches, same with the potentiometers. It should make a big difference.
 
Chuck(G) said:
If the thing was filthy (sitting in a basement or garage), there's likely some corrosion on the switch contacts and/or dirt in the pots. Get an aerosol can of contact cleaner (you usually can find something in the auto section of most big-box stores), open the case up, spray some on the switch contacts and rotate the switches, same with the potentiometers. It should make a big difference.
Click to expand...

Chuck, that's exactly right. When I say filthy, I mean FILTHY. Like a 1/8 layer of grime on the unit's face since it was sitting face up for how long.
But the good news is, I was playing with it, and the screen does work. As Chuck predicted the switches are VERY dirty and you can tell. I have some contact cleaner I bought from Radio Shack a while ago, maybe I'll try that on it.

Here's a video if anyone wants to see. Forgive me figuring the knobs out. The corroded contacts added to the learning curve. I did manage to center the little dot on the screen. I'll do what uniballer recommended and search for those probes.

http://www.youtube.com/watch?v=kSTlvTDuGDs&feature=share&list=UURsD10iMZqKtjS37EYwQBaQ
 
There are 2 documents published (for free) from Tektronix you should download if you want to learn something about oscilloscopes. These have been around for years and have been a great help to newbies.

http://socrates.berkeley.edu/~phylabs/bsc/Supplementary/Lab1/xyz_scopes.pdf

http://www.testequity.com/Images/new/tektronix/probes/ABCs_Probes.pdf

When ordering probes, make sure you match the capacitance of the probe with the input of your oscilloscope. Many probes have a compensation adjustment on them. If the capacitance isn't matched to your scope's input, you'll get a distorted waveform.
Figure 1.11 at the top of page 13 of ABCs of Probes shows what uncompensated square waves can look like.

Be aware that you need to know something about the circuitry you are examining. If the scope is not setup right (switches in the wrong position), the results you get can be misleading. Put your probe in the wrong spot and you could damage the circuit you are working on or your oscilloscope or both.
 
On a 15MHz scope, I don't think that probe compensation is such a big deal. It is important, however, that the probe have an X10 setting as well as an X1.
 
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