How can I test whether my mount motherboard has failed, or whether it's the axis motor?

[irtuk]

Bit of a disappointment, first clear night in ages and I was shooting the iris nebula with NINA. The RCD switch in our house tripped and everything shuts down. After some investigations I think I narrowed it down to an outside double socket that runs power to my mount on it's pier. One of the sockets seems to have gotten damaged over the summer and by switching that socket off I could get the house up and running again.

Now I fired up the rig again and my Pegasus Astro power box is telling me that there's a short on output 1. This is the mount power. So I swapped the mount to be on output 4 which is spare and the power box promptly reports a short on that too.

So, I have now dismantled the rig completely to get everything inside, set up just the mount and mini-pc and it appears that the right ascension axis has failed. Just using EQASCOM to send some slew inputs the DEC axis will spin but the RA is dead.

I have pulled the motherboard to have a look and there appears to be some damage to one of the chips in what I am assuming is the RA circuitry, it has the letters RA printed next to it so I think its a fairly safe assumption.

This is what I am seeing, it looks to me like there is damage to that U8 chip but I know nothing about electronics whatsoever.

Is there a test I can do to check whether its the motor or the controller that has failed? I do not (currently) have a multi-meter or any electrics testing tools but Screwfix sells them and is open. I would however need someone to explain what to do with one and I do so love a trip to Screwfix on a Sunday.

[Carbon Brush]

The first and most obvious question...
What mount is it? I don't recognise it from the photo of the innards.

Difficult say from the photo if U8 has a deposit of some sort, that is unimportant. Or if the plastic package has 'leaked its guts' indicating a dead device.
A different camera angle, or you scraping the package will sort this.

Quite often mounts have identical connectors for both axes, allowing a simple exchange for identifying motor or drive chip faults.
Put the working motor on the other drive. A short time connection won't wreck the motor.
Do not put the suspect motor on the working drive. You may end up with two faulty drives.

HTH, David.

[AL1]

This looks like an EQ6 board.   It is hard to tell if the chip is damaged or is there some kind of glue on the chip?.   Replacement EQ6 main boards are available but you will want to know the motors are healthy first

https://www.firstlightoptics.com/sky-watcher-mount-accessories/skywatcher-replacement-motherboard-with-usb-for-eq6neq6-pro-mounts-inc-non-usb-models.html

Edited November 12, 2023 by AL1

[irtuk]

ah sorry yes its a Skywatcher NEQ5 and the motherboard has SYNSCAN EQ6 Motor Controller Rev C printed on the other side.

I have just scraped that chip with my fingernail and the deposits have come off! it looks pretty clean so, not looking like that chip has exploded or been damaged. 

It also appears that the mount is now working again! Maybe just sitting inside for a while has sorted something out!!

Anyhow thanks all for your posts. Just got to reassemble and wait another few months for a clear night!

Ed.

[Synchronicity]

It could have been a small amount of corrosion on a connector that has cleared with removal and refitting.

The two first steps I use in fault finding are checking the power and removing/replacing any connectors I can get to.🙂

Michael

[malc-c]

It does look as if the driver chip has had a melt down of sorts. Ed,  if it proves that the return to life is temporary then drop me a PM and I'll replace it with one from one of the dead boards that has been sent to me which turned out to be beyond repair.  These boards have very little surge or over voltage protection, often relying on a diode to act as a fuse, which results in a completely dead board.  Other issues is damaging one or both PIC micros by placing 12v on the communication lines when using the wrong EQDIR type lead or USB convertor.

[Carbon Brush]

+1 for @Synchronicity comments.
The common drive assemblies all use cheapie connectors. No gold other non corrosive plating. No sealed assemblies. Then we let them get damp.

When you reassemble, put a bit of silicon grease in the contacts to inhibit further corrosion.
You don't have to be neat and tidy. An electrical or food grade grease won't harm plastics.
Alternatively petroluem jelly - vaseline.
If you use car type greases you risk reaction with plastics in the long term.

I regard the corrsion prevention as an 'always do this' process, whether dealing with scope stuff, changing a car bulb, or opening a car electrical connector. 

HTH, David.

[Mandy D]

36 minutes ago, Carbon Brush said:

If you use car type greases you risk reaction with plastics in the long term.

Regular oil based greases as used on cars also tend to be non-conductive, so defeat the object of the excersize. As you suggest, petroleum jelly works very well.

[The Lazy Astronomer]

8 hours ago, Carbon Brush said:

+1 for @Synchronicity comments.
The common drive assemblies all use cheapie connectors. No gold other non corrosive plating. No sealed assemblies. Then we let them get damp.

When you reassemble, put a bit of silicon grease in the contacts to inhibit further corrosion.
You don't have to be neat and tidy. An electrical or food grade grease won't harm plastics.
Alternatively petroluem jelly - vaseline.
If you use car type greases you risk reaction with plastics in the long term.

I regard the corrsion prevention as an 'always do this' process, whether dealing with scope stuff, changing a car bulb, or opening a car electrical connector. 

HTH, David.

Off topic excursion, but your comment reminded me of an experience some years ago where my motorbike wouldn't start one day after work - lights and dash all came on, but no fuel pump prime and no crank. Oh dear, I thought, this could be expensive... I then had the thought to just check the killswitch as I'd heard about issues with corrosion causing this sort of problem. Upon opening the housing I saw no corrosion, but discovered a piece of dried leaf had somehow got in there and managed to wedge itself perfectly between the contacts!! Once de-leafed, function was returned and off home I was able to go.