[Coco] RGB to VGA boards, test equipment needed

[Steve Batson]

I'm not a video export, but I'm going to guess these are way too slow 1mhz.  They say good for audio, which makes sense. Video signals are going to be much higher than 1mhz.  I don't own a scope myself and it's been years since I even used one...if I were to buy one today, I'd want a decent 100mhz Dual Trace scope with all the trimmings. :)   But I don't currently have the need.
 


On Sep 6, 2015, at 1:19 PM, Kandur <k at qdv.pw> wrote:

> Would these pocket oscilloscopes do for checking video signals?
> If yes, wich one is better? Are there any others under $100?
> 
> http://tinyurl.com/p9jx2ec
> 
> http://tinyurl.com/ommymqs
> 
> Frida y, September 4, 2015, Barry Nelson among other things wrote,
>> At 15khz a .1 uf capacitor has an effective impedance of 106 ohms but at the
>> color burst clock frequency of 3.58 mhz, the same capacitor has an impedance
>> of 0.444 ohms. Since the CoCo 3's composite video output circuit has a 10 ohm
>> resistor on the collector of the output transistor and a 120 ohm resistor on
>> the base, putting a .1 uf capacitor from the video output to ground should
>> effectively ground out the high frequency color burst signal and part of the
>> black and white video, but should leave the horizontal and vertical sync
>> pulses virtually untouched. This should eliminate the jitter on the 80 column
>> screen. If the capacitor doesn't do it by itself you could a small 10 ohm in
>> series. This has the advantage of providing sync as well as a proper black level reference signal.
> 
> Thanks,
> Kandur
> 
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