Gday Allan
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I think the first thing to do is to try & re-create the fault indoors by
putting a lens in front of the QHY9 & using a LED as an artificial star.
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We ran the unit with a fully exposed sensor and couldnt get data, let alone an image. I was expecting at least a saturated image, but didnt even get that.
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It annoys me that I always had this problem from brand new.
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In this case, the unit had been working OK, then slowly died over a few minutes, so i do suspect something else. He was sent the voltage setting pdf to try that first, but what we saw simply doesnt match expected
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One solution could be to put an external pot in place of the PCB mounted
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Dunno about your unit, but on the 8L, that pot is TINY and very sensitive.
It is also inside the cooled chamber section and i assume that is more for thermal stability, as it would have been much more sensible to have it external to the sealed chamber otherwise.
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I'll have to get on to this job - & take pictures of waveforms etc to help others.
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Have attached what we got with the unit at first.
Tweaking the pot merely appears to adjust the DC biasing of the trace
( Looking at your linked doco for the QHY9, i see their vertical scale is 2V, ie the waveform is really 4V pk-pk. I cant read the scale in the 8L pdf, but had deduced thats what we were expecting, and it was merely a bias tweak we were doing )
Andrew