Need Info/help with a Heathkit Oscilloscope model io 4540

You can buy copies of the manual from

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Thanx for those websites Dave.

Now all I need to do is track down some probes.

Ren-

As I understand it, there are two main types: direct and low capacitance. (You might also want an RF detector probe.)

The low capacitance probe has a voltage divider with a variable capacitor so you can adjust the division ratio at higher frequencies. Some scopes supply a square calibration waveform for use in adjusting the probe, so the waveform is flat with no peaks or rounded corners.

Such a low capacitance probe must approximately match the input resistance and capacitance of your oscilloscope. Typically you will multiply a reading by a factor such as ten, to find the actual voltage.

If you come across such probes at a Hamfest, there is a good chance they will work.

Fred