Re: 485 super weak brightness control


Ozan
 

https://photos.app.goo.gl/rV6gSvehN2uzbaes7


This is what I get, the a sweep signal is very weak, under 20mV at the back
of the scope but it looks fairly close to what you get
What is the time/div setting? Your gate pulses are about 2x the length of what I measure in 1ns/div setting.

Polarity of the sweep is opposite of what it should be (note that internally it has a negative slope but BNC amplifier Q942/Q944 has an inverting gain). Given that you are seeing a much smaller signal and opposite polarity probably you are just seeing feedthrough and A SWP OUT amp is not working.

Is the top waveform B gate and bottom waveform A gate? Delay between them is too much for 5/2/1n setting. I measured 27.6ns, you are looking at 200ns+.

Ozan

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