eq3-2 dual axis motor drive fault

[mac-cloud]

Hi, I've been running my Skywatcher EQ3-2 dual axis motor drive off a 6 volt adapter and accidently plugged in a 12 volt adapter the other evening and something went pop! in both the adapter and the drive. Now no life in either. Not too worried about the adapter as it was cheap but wondered if anyone had an idea on where may be the first place to look for damaged component/s in the drive controller? I've opened it up and there are no obvious burn marks or blown solder. I recently adapted this drive so that it would connect to PHD via interface so would like to get it operating if possible. Thanks, Rob

Meant to add, with 6 volt adapter connected I get 6 volts at supply when switch in off position. This drops to 3.6 volts when I switch drive on but no LED or power at motor/s.

[Alien 13]

The EQ3 circuitry offers no protection against over voltage which is one reason it runs fine off 5V from a power bank, the only suggestion is to look up the chips that are used on google and find the supply pins, check that these are getting the 5-6V first. 

Alan

[mac-cloud]

Thanks for that info. I'll check this out.

Rob

[JamesF]

Sadly I suspect the microcontroller may be a bit of a mess and I'm not sure there's any easy fix for that.  It's been a few years since I opened my controller up, but I don't think there are many other components inside that would be sensitive to the higher voltage.

James

[mac-cloud]

Hi Alan,

I found info on the chip and am getting voltage on the supply pin. I checked the outputs where the cables leave the controller and they are sitting at about 3.6 volts. Shouldn't they be continuously changing to get the steeper motor to rotate? If so does this point to the chip being damaged? Also the outputs start heating up after a short while. Thanks.

Rob

[Alien 13]

12 hours ago, mac-cloud said:

Hi Alan,

I found info on the chip and am getting voltage on the supply pin. I checked the outputs where the cables leave the controller and they are sitting at about 3.6 volts. Shouldn't they be continuously changing to get the steeper motor to rotate? If so does this point to the chip being damaged? Also the outputs start heating up after a short while. Thanks.

Rob

It looks like the chip is damaged causing the outputs to sit at logic 1, does the chip info detail its max supply voltage? 

I am assuming you have the original controller rather than the enhanced one so you might get lucky in finding a second hand one.

Alan

[mac-cloud]

Hi Alan,

The chip is a GMS97L51 which reading elsewhere is an 8051 based microcontroller. According to the datasheet the L stands for low voltage with an operating voltage of 2.7 - 3.6 volts so not sure why the hand controller is designed for a 6v supply. So looks like 12v would have damaged the chip for sure. I've got another newer controller of the same type but didn't want to have to start taking it apart and modifying it (soldering wiring to the ra/dec switch terminals for auto guiding), looks like I probably will though. Thanks for your help.

 

Rob

[JamesF]

19 minutes ago, mac-cloud said:

The chip is a GMS97L51 which reading elsewhere is an 8051 based microcontroller. According to the datasheet the L stands for low voltage with an operating voltage of 2.7 - 3.6 volts so not sure why the hand controller is designed for a 6v supply.

Possibly the motors require the higher voltage?  I'd be inclined to agree with your diagnosis though.  I think the microcontroller is very likely to be dead.

If you're opening up the box and doing soldering work inside, I wonder how practical it might be to add a 6V regulator in line with the power input jack?

James

[Alien 13]

From memory I did look at putting in some over voltage protection but as the unit would in theory run off 4 rechargeable cells at 4.8V I decided to use very cheap 5.2V mobile phone power banks instead and never looked back. I currently have a 10Ah one that could power it continuously for around  25-40 hours.

Alan

[mac-cloud]

This sounds like a good idea, but I don't think there would be much space available to mount it as I think a couple of capacitors would be required in addition to the regulator. I think I'll just have to be more careful from now on. Thanks.

Rob

[JamesF]

I have a niggling feeling that I changed the power supply socket on mine so that it wouldn't match my 12V supplies.

James

[mac-cloud]

I was actually thinking about this also today so that's what I'm going to do. Thanks.

Rob