Quote:
Originally Posted by Username1
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If all else fails, you could spread out that overshoot part of the scope pic & measure
the frequency of the oscillation & make yourself a filter to ground it out.
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I replaced the capacitor on the base of Q402 (0.0022uf) with a 0.003uf cap and it flattened the overshoot (so now the waveform lookin right).
Unfortunately, it made absolutely no difference to the lines on the raster. They remain ever unchanged.
Also worth noting is that the output of the H transistor Q404 looks nice an tidy.
With such a clean wave, the only place that Q402 could make a difference is polluting the 135V I think, which seems okay. It's got a tiny bit of noise , but it looks reasonable.
Maybe the weirdest thing I found is that the 178V looks really noisy on the other side of L521. Not sure if this is expected, but it's on the neck board between the inductor and the three resistors which feed the output transistors.
Here's the spot in the schematic. The sam's has the inductor on the main board schematic, but it's actually on the neck board. It leaves the PCB at point 39.
On the left side of L521, it looks fine, but on the other side of L521 it has this 40Vpkpk 60Hz waveform. I guess it's the raster. It's probably normal, but I haven't looked at that many different cathode voltages in my life.
