Hi Guys,
Got this one today:

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How do I know how slow it is? I've never used a scope.
I can provide a logic pulse.
How do I know the limits of what to connect it to?
I take it you can't just plug it into a mains socket to look at a 50Hz sine wave.

If I know how to connect it to something,
I do have half an idea about what ti does,
shows us signals that are too fast for us to see.

This brand has a good reputation. The manual is available online free from several places (search BWD 539C) and will give you the specs and procedures.

You'll need probes for each channel, but they are readily available at Jaycar or similar.

Maven

It's going strong

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I could only find the manual for 539D which is 1976, so I'll assume '75.
This is great, even with microcontrollers, I haven't done anything faster than this anyway.

It did come with probes of different types, some are shabby, and have been repaired,
but that looks like something high voltage,
where I'd mainly look at logic levels, and want to investigate
what can be seen in a radio.

Why is it not Earthed? We are I the '70's now!
The Earth pin is shaved off the plug so neatly that it could
have been the manufacturer that did it..

Some tech probably ran into a "ground loop" problem, and decided to remove the earth pin off its power cord to solve it. Here in the USA, we have 3 pin to 2 pin adapters, so a piece of equipment that comes with a grounded 3 prong plug can be plugged into an older two prong outlet (power point). And we'd use these to break the ground pin connection (by not connecting the ground tab to the outlet mounting screw) rather than cut the pin off.

It would be nice to at least have the option to tie it back,
it's not even legal here, I don't think.. unless double insulated plastic cabinet which this is not.

You could replace the old plug (does it use an IEC cord, often seen on PCs) to restore the earth connection, and also get a 2nd plug, and a female socket to create an extension cord, but "forget" to connect the earth wire in that extension cord, if you want no earth connection (if you get a ground loop problem).

That is the plan, I have the probes now, and have found some fun things in an RF circuit.
The most interesting was looking at one end of a crystal osc used in real time clocks.
32.something kHz.

The extension cord would make the appliance legal here so that's the way to go.
Just have a dodgy extension cord, not a dodgy appliance.
It might be wise to think about how to associate the extension with the scope
to prevent it ending up in use with anything else.

In contrast, I got some modern junk today.
It wasn't even on the sidewalk, I had to go to a shop and pay for it.

Jaycar experimental radio IF is 455 kHz

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The extension cord would make the appliance legal...

Correct, though the extension cord is illegal if put to use without the earth conductor. You would also be liable to prosecution if the use of the cord lead to injury or death. Additionally, your home and contents insurance is void if the lead feeds an appliance that starts a fire. Food for thought.

An expensive but safer way to go about all this is to buy/borrow and use a portable scope which requires no mains power except for recharging and use the older machine for situations that don't disrupt its ability to give accurate readings.

Yes, and I would never want to forget when the thing
wasn't earthed either, and then leave it that way.
Modern powerboards know when the earth is connected
in case the connection failed somewhere in your home.
That might be a circuit worth looking into.

The sneakier thing to have done (the original owner) would
have been to disconnect the lead inside the original plug.
That could have worked it's way loose somehow.

As much as I'd love one of these:
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the toy budget is fast running out after today!

I have a 539C Dual trace, needs one pot replaced (not easy)
I actually got its original paperwork. Test date 20/1/76

DC 20MHz
Input Impedance 1Meg 35pF
Input Volts (Max.) 400V DC 280V AC RMS

There is not a simple explanation for the many uses of the CRO but not a lot fixing radio's.

I use mine more for alignment, as you can see what the wave form is up to as well as measure its amplitude.

However, one of them was used recently to sort out the mess in a Model 59 STC chassis, as it came half repaired with bits undone & missing and a factory stuff up.CRO did show the oscillator working (autodyne) and where the signal disappeared as well as distortion.

Marc

Dear Art.

The earth pin of your Oscilloscope was probabilly removed to allow it to be used on live chassis TV's when the TV was not connected to an isolation transformer.

This would happen if, The serviceman did not have an isolation transformer of sufficient wattage.
The serviceman did not have an isolation transformer.
The TV was of the half wave type. These would cook a transformer by the non-balanced waveform.

Your post prompted me to look at my oscilloscope. Yes, the earth pin is cut off.

If working on one of the highly desireable European CTV's of the mid 1970's check as to if the chassis is live, full wave, half wave. Caution. These sets suck a lot of power, and can cause one's variac to exude clouds of smoke if your variac is not of four amps or greater.

Wayne