Hello,
I've been watching the EEVBlog for a while. Sorry my first post in this forum is an ask for help...
I've taken an old TV monitor (you know, a TV from the 80s that doesn't have a tuner...) and have been converting it into a vector display.
I bought a Sparkfun O-scope clock to get a test image from, and used LM3886s to built a simple current amplifier to drive the deflection coils. I also disabled the blanking on the display and rewound the coils to drop the inductance.
The amplifiers are basically this:
http://spritesmods.com/?art=bwidow_fpga&page=4without the goofy input crap.
I attached the image I get below.
Question is, does anyone have any suggestions on how to get this thing under control? You can definitely tell its a clock, but I'm not sure I understand why there's so much distortion.
I took an oscilloscope to between the output of the op-amp and ground, and it looks very clean. However, when I use the 2 add-invert across coils to get the true voltage (because the shunt could throw it off), I see what I think are large voltage spikes from the inductance of the coils. I wonder if that's the problem? I haven't been able to blank the beam on demand, so I don't know how big of an impact that will have on the image...
I've been fighting this off and on for a few months and thought I'd ask some people who know what they're doing. Any suggestions on where to go?