HEQ5Pro performance

[Robert9 (Robert)]

Hi,
A few nights ago I ran into trouble with my mount coming up with erratic behaviour. Wouldn't align, couldn't find targets, wouldn't park properly.
I had some discussion with Raymo who, having had problems with his mount, suggested that a capacitor on the motor control board (MCB) might be to blame. So, I pulled it all apart, checked all that could be checked and couldn't find a thing wrong. Reassembled and tested and all seemed OK.

Then I tried an alignment test and was very surprised by the result.

Powered up the unit and performed a 2-star align however, I just accepted the positions that the mount went to without any adjustment to DEC or AZ. (I was using ACrux and Achenar as alignment stars). After seeing on the HC that I had a successful alignment, I then followed through to the report which said El 4'50", Az 26'17". Without changing anything I repeated the alignment with the same targets and then got El 4'13" Az 21'26". Further repeats continued to give differing results.

I parked the scope and restarted without resuming from park and did another 2 star alignment. Same results El 4'55" Az 19'28".

I did a GOTO to Formalhaut then the moon and this worked OK. Did another alignment, El 6'23" Az 22'11"

Now I would have thought that considering I had accepted the mount's positioning, it would have come up with 0'0" for El and Az each time. So, is this just an effect caused by imperfections in the drive mechanism or is there something wrong? Alternatively, have I got it wrong in my poor ageing head?

I would love to hear form anyone who might have tried or is willing to try this test on their mount - irrespective of model.
Robert

[raymo]

You are getting nonsense error readings on both axes, and since the R.A.
and Dec drives are separate systems, the likelihood of both developing faults simultaneously is vanishingly small. The only likely fault is a gear retaining screw coming loose allowing the gear to cause a lot of backlash, and that, of course, would only affect one axis. The only connection between the systems is electronic, so the fault must lie either in the MCB or the hand controller.[ or just possibly a cable or one of it's connections]. I just remembered that several years ago there was a spate of faulty hand controller to mount cables; mine was one.
If your only problem is error readings, then the problem almost certainly lies in the MCB, as the hand controller only relays the
readings from the MCB to your LCD screen; it takes no active part in producing those readings. It only sends instructions to the motors when
using the control buttons or using Go To. I gather you put a meter on the
capacitors; if so, were the readings significantly below the 470 stated on the components? As you are aware, that caused my problem, which was
seemingly identical to yours. Hopefully someone will get you over the line eventually.
cheers raymo
P.S. Unfortunately I'm not at home, so cannot run the test for you.