Will this scope do the job

[TinCanAlley]

Okay, I got the scope, but not my brother to operate it. He did give me the manual, though. So is this scope going to be enough for me to do my Avanti? I'm attaching a couple of pics. It isn't state of the art, that's for sure.

[bob91343]

That oscilloscope is okay for checking waveforms and making adjustments but don't count on it to make measurements with any degree of accuracy. Look at the specifications to determine the bandwidth and then use a probe with it for any serious purposes.

[TinCanAlley]

Originally Posted by bob91343

That oscilloscope is okay for checking waveforms and making adjustments but don't count on it to make measurements with any degree of accuracy. Look at the specifications to determine the bandwidth and then use a probe with it for any serious purposes.

Main goal is to use it to compare waveforms from the SM to actual in the horizontal blanking and convergence circuits. The SM mentions 7875 and a squiggle after it and the manual for the scope says that horizontal should have a cps sweep of 7875. Is that what you mean by bandwidth? If so, it seems that all the circuits I need to test are either 30(squiggle) or 7875(squiggle). If you know what the squiggle is actually called, please tell me. I'll feel so much better being able use the proper terms.

Also, in one of the pics I attached there's a probe in the bottom right. It came with that and standard leads like a DMM. Is the probe needed for checking the horizontal pulses and the convergence board waveforms?

I've never used one before, so I'm pretty much flying by the seat of my pants.

[bob91343]

No, the bandwidth to which I am referring is vertical bandwidth. If it's at least 5 MHz you are okay. The 'squiggle' means Hz. It's a tilde and is meant to look like a little sinewave cycle.

I can't see the probe in the pic, too dark. The probe you want is needed to avoid screwing up the circuit you are measuring. The usual test leads won't do.

I would recommend you scrap this and get a modern unit with nice probes; these are available cheaply enough. In fact an old Tektronix tube unit should go for under $50 if it's not a rare model or one of the big jobs.

Some of the main problems in those old units are sweep nonlinearity and lack of calibration, both horizontal and vertical. If you view a sinusoid you will see it compressing toward the right, as the 'sawtooth' imperfections become more apparent. And you have no idea of the frequency, nor of the the amplitude, without some kind of calibrator. In addition, synchronizing the sweep so as to see a steady display is often a challenge.

Having said all that, you can, if you are careful, use it for a lot of things beyond its basic capabilities. You just have to realize its limitations and work around them.

[TinCanAlley]

Originally Posted by bob91343

No, the bandwidth to which I am referring is vertical bandwidth. If it's at least 5 MHz you are okay. The 'squiggle' means Hz. It's a tilde and is meant to look like a little sinewave cycle.

I can't see the probe in the pic, too dark. The probe you want is needed to avoid screwing up the circuit you are measuring. The usual test leads won't do.

I would recommend you scrap this and get a modern unit with nice probes; these are available cheaply enough. In fact an old Tektronix tube unit should go for under $50 if it's not a rare model or one of the big jobs.

Some of the main problems in those old units are sweep nonlinearity and lack of calibration, both horizontal and vertical. If you view a sinusoid you will see it compressing toward the right, as the 'sawtooth' imperfections become more apparent. And you have no idea of the frequency, nor of the the amplitude, without some kind of calibrator. In addition, synchronizing the sweep so as to see a steady display is often a challenge.

Having said all that, you can, if you are careful, use it for a lot of things beyond its basic capabilities. You just have to realize its limitations and work around them.

This is the probe. It was included with the standard leads.

I really am not in the market to purchase one as once this is done, I don't know if I'll ever need/use it again.

I'm also attaching a pic from the SM of what I'm needing to see on a scope. Is this something I will be able to see with this one?

Thanks

[N2IXK]

The Heathkit O-11 has a 5 MHz bandwidth, and color TV servicing was one of the intended applications for it. It is pretty typical of the scopes used by TV shops back in the day. Tektronix stuff was WAY too expensive for the typical TV shop.

As long as the scope still works, it should be fine. The biggest pain about using those old service grade scopes is the lack of calibration on the vertical attenuator and horizontal timebase. You can't be sure of actual amplitudes or frequencies with one of these things. A better grade scope will have vertical amplitude controls marked in V/division and horizontal sweeps in time/division so you can make actual MEASUREMENTS with the scope, not just see the waveform.

[Username1]

Been watching you guys.... That scope will be fine for what you are doing.... Main thing is that you will be connecting that ground lead to some ground (metal chassis part) on your tv. Before you connect it, take a volt meter AC 250v scale, and connect one lead to the ground on your tv, and the other lead to the ground lead off the scope... If you read a voltage... like 120v then you need to reverse the plug in the wall off one of your items, as you have a hot chassis on those items.... Then measure it again, the voltage should be gone, or very low... If there was no voltage to begin with then don't worry about it.

Anyway, your just looking to see that the pulse is getting through. 30v at 15,734hz and 30 at 59hz. That scope will show it to you fine.

The sweep rate 7875 and the other one are Sam's own favorite rates they always print those numbers, its just so they can show a few frames of the recurring pulse.... It will be 1/15734 the horiz scan rate, and 1/59 hz the vert. refresh rate....

A few pretty good oscilloscope tutorials:

Oscilloscope 101 if it don't put you to sleep:
http://www.youtube.com/watch?v=WiNpGZaJArA

If you had a modern scope you could measure DC like this:
http://www.youtube.com/watch?v=vFqxn6VGYC0

Signal measuring & frequency:
http://www.youtube.com/watch?v=zQDuZ3a6HAE

Here is a cool thingie about bandwidth:
http://www.youtube.com/watch?v=oZ1Dv2dVGkU

Here's something you'll never need....
http://www.youtube.com/watch?v=pGwL6FadC9U

ok, I spent too much time on youtube today.....

Lots of really good electronics stuff on youtube.......

[bob91343]

That probe could be anything. If it's a demodulator, it won't do. The probe you want is an attenuator, usually 10:1. Many 10:1 probes have a switch that selects 10:1 or 1:1. A demod probe might have a switch for direct and demod.

[TinCanAlley]

Originally Posted by bob91343

That probe could be anything. If it's a demodulator, it won't do. The probe you want is an attenuator, usually 10:1. Many 10:1 probes have a switch that selects 10:1 or 1:1. A demod probe might have a switch for direct and demod.

Found the instructions for the probe. It says it permits you to observe signals that would otherwise be affected by the relatively high input capacitance of standard coaxial leads. Also says the signal attenuation is accurate to within 5%.

So I believe this probe is the one you're speaking of.

[TinCanAlley]

Originally Posted by Username1

Been watching you guys.... That scope will be fine for what you are doing.... Main thing is that you will be connecting that ground lead to some ground (metal chassis part) on your tv. Before you connect it, take a volt meter AC 250v scale, and connect one lead to the ground on your tv, and the other lead to the ground lead off the scope... If you read a voltage... like 120v then you need to reverse the plug in the wall off one of your items, as you have a hot chassis on those items.... Then measure it again, the voltage should be gone, or very low... If there was no voltage to begin with then don't worry about it.

Anyway, your just looking to see that the pulse is getting through. 30v at 15,734hz and 30 at 59hz. That scope will show it to you fine.

The sweep rate 7875 and the other one are Sam's own favorite rates they always print those numbers, its just so they can show a few frames of the recurring pulse.... It will be 1/15734 the horiz scan rate, and 1/59 hz the vert. refresh rate....

A few pretty good oscilloscope tutorials:

Oscilloscope 101 if it don't put you to sleep:
http://www.youtube.com/watch?v=WiNpGZaJArA

If you had a modern scope you could measure DC like this:
http://www.youtube.com/watch?v=vFqxn6VGYC0

Signal measuring & frequency:
http://www.youtube.com/watch?v=zQDuZ3a6HAE

Here is a cool thingie about bandwidth:
http://www.youtube.com/watch?v=oZ1Dv2dVGkU

Here's something you'll never need....
http://www.youtube.com/watch?v=pGwL6FadC9U

ok, I spent too much time on youtube today.....

Lots of really good electronics stuff on youtube.......

Thanks! Looks like I've got some videos to watch. Just have to figure out how to set the knobs. I believe I've found one of the test points for the horizontal blanking circuit that is also the test point for the vertical. They've connected the vertical blanking collector to the horizontal blanking base and that's where I'm supposed to probe. Would this be a standard lead or should I use the probe?

[TinCanAlley]

Originally Posted by N2IXK

The Heathkit O-11 has a 5 MHz bandwidth, and color TV servicing was one of the intended applications for it. It is pretty typical of the scopes used by TV shops back in the day. Tektronix stuff was WAY too expensive for the typical TV shop.

As long as the scope still works, it should be fine. The biggest pain about using those old service grade scopes is the lack of calibration on the vertical attenuator and horizontal timebase. You can't be sure of actual amplitudes or frequencies with one of these things. A better grade scope will have vertical amplitude controls marked in V/division and horizontal sweeps in time/division so you can make actual MEASUREMENTS with the scope, not just see the waveform.

Yeah, inside the manual it has a section about TV testing. Wish it went into detail, but it's a start.

My brother says it works and is calibrated. We'll see.

[bob91343]

Yes that's the right probe. It will reduce the loading effect of the 'scope in exchange for reduced sensitivity. A good tradeoff much of the time.