Re: 485 super weak brightness control


Ondrej Pavelka
 

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

On Mon, 22 Mar 2021, 18:57 Ozan, <ozan_g@erdogan.us> wrote:

One more question, the A sweep is triangular but the B sweep has a flat
top
and becoming almost square, that doesn't look right?
I can't access B sweep without taking the case off so I don't know the
exact shape but it should look similar to A sweep. A sweep maxes out at
10ns/div, B sweep can go 2ns/div (then there is a 2x multiplier in
horizontal amp for 1ns/div) so the ramp is faster on B-sweep at 5/2/1n.
Expected waveform is about 1V per time division. If you are sure of the
measurement setup this could be the problem.

Is my understanding correct: In 5ns/div with "B horizontal mode" you see a
good B sweep but with "A horizontal mode" setting B sweep at R1322 looks
distorted?

Were you able to look at A-gate/A sweep/B-gate signals and compare with
the picture I sent?

Ozan






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