Re: Debugging Dec failure to move w/1200 CP3


That is exactly what George means. We are trying to determine if the issue follows the motor itself, indicating a bad motor, or the wire harness. If it follows the wire harness, then the issue is either the harness itself or the CP3. If the problem only occurs when the cable is moved a certain way, then the harness itself should be the issue.

Liam Plybon

-----Original Message-----
From: <> On Behalf Of Dale Ghent
Sent: Thursday, July 29, 2021 10:45 AM
Subject: Re: [ap-gto] Debugging Dec failure to move w/1200 CP3

Right. What George is saying is that you can unplug the dec cable from the dec motor and plug it into the RA motor. If the problem follows with the cable move, then the issue is quite likely a cable problem - a broken internal wire or solder connection inside the connector.

Sure you can take a multimeter to each pin and test for continuity but you might need that 3rd hand to flop the cable around while you test each pin's continuity because the issue might rear its head only when the cable is flexing under movement. Just swapping it to the RA motor and trying to induce the issue there is often a quicker way to determine this.

On Jul 29, 2021, at 11:13, Steven Panish <> wrote:

Not likely. The problem is only on DEC. RA is unaffected and when DEC is failing I can nudge in DEC just fine, and tracking is fine (in RA). So I don't see how it could be the 12V power to the CP3. I think it has to be either in the CP3 guts outward to the DEC motor. I'll do the cable swap and maybe ohm out the cable first.

Are there any known points of failure in that path?


On Thu, Jul 29, 2021 at 11:00 AM George <> wrote:

Remove the power cable from the CP3 control box and note that the center pin is a split pin. Spread the two halves with a jeweler’s screwdriver or the tip of a knife blade. See if you still encounter an issue. If you do, then reverse the RA and Dec cables and see if the issue is with the RA instead of the Dec.

Let me know directly at my AP email below.



George Whitney

Astro-Physics, Inc.

Phone: 815-222-6538 (direct line)

Phone: 815-282-1513 (office)


From: <> On Behalf Of Steven Panish
Sent: Thursday, July 29, 2021 9:54 AM
Subject: Re: [ap-gto] Debugging Dec failure to move w/1200 CP3

Although now that I think about it, swapping will be tough test. The problem comes and goes intermittently. I may have to wait for it to really break. Maybe flexing the wires would provoke it.


On Thu, Jul 29, 2021 at 10:49 AM Steve Panish <> wrote:

Good idea Dale. I dont' know the pinout, so wasn't aware this would be possible.

On Thu, Jul 29, 2021 at 9:49 AM Dale Ghent <> wrote:

Could be the dec cable has developed a connection fault in the form of a broken wire. Swap it with the RA cable and see if moving the dec axis continues to have problems.

On Jul 29, 2021, at 09:42, Steven Panish <> wrote:

Help! My 1200 CP3 is intermittently not responding to DEC move commands, either manually from the V2 driver window or the handbox, or via PHD2. I've unplugged the DEC motor connections and put contact cleaner on the exposed pins, which did not help. Would appreciate help debugging. It happens a couple times per evening and resolves itself after a minute or two.


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