Quote:
Originally Posted by alpal
posted on this thread 21-02-2015, 02:03 PM with pics
I opened up the camera & made the adjustment.
The value of the Pot R27 is 100 ohms.
The info provided by QHY is misleading.
They say 2.2 Volts but their Oscilloscope documents show 2 + .2 of a division
( because they are on 2 Volts per centimeter ) which is actually 2.4 Volts.
When I checked my QHY9 it was 2.4 Volts but the waveform does not look
identical to their picture.
I used 1 volt per centimeter to get more accuracy.
I can't see any ringing on top of the waveform but maybe my CRO doesn't have the bandwidth..
I adjusted it to 2.2 Volts & will test it at the first opportunity
to see if the black horizontal lines on bright stars have gone.
I bought 2 different types of 100 ohm preset pot so that I could install
one of them at an external location but I will see if the above works first.
I added 2 giant photos on flickr of the 2 PCBs - top & bottom.
see pic:
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Update 29th January 2017.
The QHY9M horizontal bleed line problem is solved.
I took 2 pics & posted them here on the forum:
http://www.iceinspace.com.au/forum/s...d.php?t=152997
The trick was to adjust the pot R27 here:
https://www.flickr.com/photos/247194...in/photostream
to get the correct waveform &
then only use slow download - about 12 seconds.
Don't tick the box for fast download when in capture mode.
( Actually it says that in the book but it should be in giant letters - I missed it.)
Also - the slow download has far less noise than fast download.
The dark noise on fast download is about 4225 bit count of the maximum 65536 bit count
whereas the dark noise is only about 1029 bit count for slow download.
4000 is about the average sky noise so you get a considerable advantage in signal to noise ratio too.
see the attached pic showing the difference using NASA FITS liberator & centering
the slider in the middle of the noise hump of 2 dark frames
depending on the readout speed.
Left hand side is slow readout speed & Right hand side is fast readout speed.
cheers
Allan