Quote:
Originally Posted by RobF
I thought you were doing or had done a belt mod on the EQ6? Must still be looseness in the gear mesh?)
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I have. Present theory is there may be slop in the belt. The final installation of the stepper against the belt is completely blind. There's every chance that when I put it in the belt was riding along the top ring on the motor gear and slipped after a bit of using. It's easy enough to check so that's on my todo list tomorrow.
Quote:
Originally Posted by alpal
Hi Chris,
Fair enough.
I was only giving you ideas - I didn't know that you had already tried that.
While PHD is calibrating it is obviously doing so when there is not
a rapid excursion problem -
so it is not seeing that problem & sets in the gain of the system
for a normal situation.
It then cannot handle the sudden rapid excursion which
is probably caused by a Dec backlash issue. ( or some other mechanical issue )
It could be anything: a bit of grit on the worm wheel or
a maladjusted Dec axis.
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No, I appreciate you throwing ideas at me. Thanks.
To be clear I'm not trying to correct for the excursion problem in PHD. Looking at the magnitude it's not a correctable issue, I'm trying to identify the source of the problem, and I'm not convinced it's not a software issue. By that I mean computer doing something stupid, not a specific setting like gain (because close inspection of the graph shows no guide commands preceding the spike).
I think this simply because there so far is no discernible period. Also it did it before and after my hypertune / belt mod and I was very VERY careful to inspect the worm for damage.
Anyway it didn't happen yesterday. Weather permitting I'm going to rule whether the spiking issue is resolved by imaging half the night then undoing my change and imagining again and seeing if it causes a problem.
Also I'm going to check the steppers against the belt tomorrow, and if that doesn't fix it I think the DEC axis is coming apart again next week to re-check shim spacing. The DEC axis has almost no play that I can feel by hand so one thought is that the gear on the worm doesn't have its grub screws in all the way. Which will suck because that's a complete mount disassembly, so last resort.