I don't know how to use a scope yet and I can tell it will take some time
to learn. I mainly dabble with older vcr's and some other consumer A/V
equipment.


I was a bench tech at one time, I think sometime in the late 1800's
:-) and I used scopes a lot. Maybe some of the current techs could
fill you in better on this, but you need to be aware of the hazards
involved in using a scope in a hot chassis. In older television sets,
for example, one side of the 120 volt input went straight to the TV
chassis. There is no power transformer in this kind of equipment. If
the AC cord plug gets reversed in the receptacle, you have 120 volts
on the chassis. If you get between that chassis and ground...ZOT!!! If
your scope probe connected to that 120 volts....ZOT!!

With much of the modern test equipment, which is handheld, battery
operated, you don't have to worry about this as much. With an AC
operated scope you do.

ALWAYS use the third prong on the AC plug if your scope has one. It's
a bonding ground and connects your scope chassis to ground. And be
sure to plug it into a receptacle with a good bonding ground. Don't
use those 3 prong to 2 prong cheaters. On a single phase circuit (120
volt), one power conductor is at 120 volts and the other is at ground
potential. Most modern receptacles are keyed so you can only get the
plug in one way. This is a basic safety step to TRY to ensure the hot
goes to hot and the neutral to ground. The third prong almost
certainly ensures this. I say almost, because your receptacle may be
wired wrong. If they become reversed, you can have a hazardous
situation.

Also, as my scope manual suggests, use an isolation transformer (if
you can afford one) when working in a hot chassis situation. This
prevents current flow directly between equipment, and maybe you and
ground. The manual also suggest connecting the scope chassis directly
to the equipment under test (bonding) with a separate conductor. Most
techs probably omit this step as being overkill. But if you're working
on a piece of equipment that uses a 2 prong AC power connection, and
you connect your probe in certain ways, you can get a ground fault
current running through your probe that might damage it, the scope
input circuitry or the equipment under test. .

Most entertainment equipment, like VCR's, don't have a bonding
conductor (3 prong plug). With semiconductor circuits in most
equipment, the DC voltages are under 60 volts and not a hazard to you.
But, you can still blow things if the scope is connected wrong. In TV
sets, it's a different story, even with solid state devices. The video
output transistors can be running well above 100 volts.

I suggest you don't work on television sets with a scope till you
clearly understand the dangers. The high voltage circuits in colour
TV's are regulated to 1 amp. At those voltages, that is lethal. Also,
the horizontal output stages have transient voltages that are not
apparent. On the older tube sets, you never used a scope or a meter
directly on the plate of the horizontal output stage. If you didn't
know that, you could be in for a dull surprise.

I'm talking worst case and I've never had any of that happen. Then
again, I was trained by responsible techs. It's good to be aware of
it, however. If the equipment you are testing only has one power
supply ground (common), you connect your scope probe ground to it. If
there are separate power supply grounds, you have to be more careful.
Always identify the ground of the supply you are measuring relative
to. Remember that you're inserting a grounded lead into the circuit.
If your connection point is above chassis ground, and the chassis is
bonded to ground, and you ground it, you'll get an unpleasant
reaction. It's not the same with DVM's, where the ground lead is not
grounded.

There is another basic rule with oscilliscopes. NEVER leave the beam
on the screen as a dot or a small area. This would only happen when
the time base is off and there is no sweep. You need to be very aware
of it however. If the beam becomes focused in a small area...like a
dot...for any amount of time, it will burn the phosphors on the
screen. You'll end up with an area 1/4 inch in diameter, burned and
useless. If you find yourself in an X-Y input situation, immediately
reduce the brilliance of the beam so the dot is barely visible. It's a
good idea to keep the brilliance as low as practicable anyway. When
you're not using the scope for any amount of time, turn it down.

Speaking of which....it's always a good idea with any test equipment
to start on a high scale and work down. I never left my scopes on a
millivolt scale when not in use. I also left the probe on 10x.

Finally, the probe usually has a direct and a 10x setting. I always
left mine on 10X since it reduces the input signal 10 times. If I
needed direct, I'd just switch over. Some probes need to be
calibrated. There's a small capacitor built in that can be adjusted.

Tektronics has always had a good name. The price you paid seems like a
decent deal. The problem with older equipment is that the
electrolytics in the power supply tend to dry out eventually. Also,
other capacitors may become leaky.