Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?
As the others said, you can do a lot with a 100MHz scope. I think that is a good place to start.
Not exactly. A 500MHz scope can display a 500MHz sine wave. You will need a lot more bandwidth to display a nice 500MHz square wave. A square wave is made up of the primary frequency plus its odd harmonics. You will start seeing something square-ish when the bandwidth is about 5 times the signal frequency. 10 times would be better.
Also, beware that many early digital storage scopes have low sample rates. For example, many early TEK and HP storage scopes have 100MS/s rates with higher bandwidth front ends. A scope like this needs to sample a periodic waveform repeatedly to show anything useful near the scopes bandwidth, so it is only useful for non-repeating signals at much lower frequencies. You generally need to sample at 4 to 10 times the frequency of your signal for non-repetitive signals.
Don't forget that the probes you use have a lot to do with what you see. The cheap 100MHz probes from ebay are fine for general purpose troubleshooting and seeing low speed signals, but to make good use of a 500MHz scope you will need serious probes, and they are not cheap. Even real TEK or HP 500MHz passive probes often may not show you what you want to see because of probe capacitance, etc.
As the others said, you can do a lot with a 100MHz scope. I think that is a good place to start.
Not exactly. A 500MHz scope can display a 500MHz sine wave. You will need a lot more bandwidth to display a nice 500MHz square wave. A square wave is made up of the primary frequency plus its odd harmonics. You will start seeing something square-ish when the bandwidth is about 5 times the signal frequency. 10 times would be better.
Also, beware that many early digital storage scopes have low sample rates. For example, many early TEK and HP storage scopes have 100MS/s rates with higher bandwidth front ends. A scope like this needs to sample a periodic waveform repeatedly to show anything useful near the scopes bandwidth, so it is only useful for non-repeating signals at much lower frequencies. You generally need to sample at 4 to 10 times the frequency of your signal for non-repetitive signals.
Don't forget that the probes you use have a lot to do with what you see. The cheap 100MHz probes from ebay are fine for general purpose troubleshooting and seeing low speed signals, but to make good use of a 500MHz scope you will need serious probes, and they are not cheap. Even real TEK or HP 500MHz passive probes often may not show you what you want to see because of probe capacitance, etc.
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