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Carboncrazy

Synscan EQ5 Both axes no response

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Can anyone help? I'm pretty much a novice at this astronomy stuff but loving the steep learning curve. I started by using camera lenses modified to use an eyepiece but after much debate, deliberation and saving up, I have finally bought my first proper telescope. Unfortunately I now have a problem.

Last year I bought a second hand Synscan EQ5 mount which has worked perfectly each time I have used it. I  used it about a month ago for the first time with the new scope (last time we had a clear sky). Everything worked as it should. At 2 am I parked the scope, dismantled everything and put it away. Nothing was dropped, snagged or got wet.

The forecast said we might get a clear sky last night. Anticipating this I got the mount on the bench, stripped, cleaned, polished and greased the DEC axis plain bearings (hoping this might help with guiding). When finished I connected the motor controller and handset and switched on. I was greeted with the following messages: INITIALISING then CAUTION BOTH AXES NO RESPONSE. If I press enter and carry on through the menus, then everything appears to be as it should except no motors run. I have tried everything I can think of and would be very grateful of advise or suggestions. These are things I have tried, so far:

Factory reset

Different power supply. I have been using a motorbike battery which is giving 13.5V constantly when I switch on. I have tried two other batteries with a 2A charger connected.

Continuity tested the cables from the plugs that go onto the motherboard of the controller all the way to the motors.

I made up the  RJ45 and RJ12 diagnostic cables suggested in the manual and the handset appears to be ok.

Removed the motors from the mount to make sure that they turn freely.

Replaced the RJ45 cable from the handset to the controller.

Examined the motherboard for dry joints and damaged components.

Assembled everything in the tripod to make sure that the earthing tab on the controller made no difference.

I now feel that the problem is the controller motherboard but logic tells me that it was the mount I disassembled, so the fault should lie there. Is there anyone who has had the same problem or who has the same system that could help me diagnose the problem. I'm in North Shropshire but happy to travel to anyone who could help. Unfortunately I don't know anyone with the same mount.

 

 

 

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My EQ5, I've modded myself, as originally it was only manual, but if your mount is the same as the EQ3 (which I have) and uses a separate driver box, It sounds like you haven't connected the motor drive cables, i.e. the DIN cable that goes from the driver box to the motors, so I'd start by making sure everything is connected & that there are no shorts etc.

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55 minutes ago, Dr_Ju_ju said:

My EQ5, I've modded myself, as originally it was only manual, but if your mount is the same as the EQ3 (which I have) and uses a separate driver box, It sounds like you haven't connected the motor drive cables, i.e. the DIN cable that goes from the driver box to the motors, so I'd start by making sure everything is connected & that there are no shorts etc.

Thanks for the prompt reply and suggestion.  The DIN cables are plugged in (I have also swapped them round) and I have checked the continuity of them from the back of the socket on the driver box all the way to the motors. I had not thought of checking for short circuit but have now disconnected the motors (as they effectively provide a short circuit) and checked each wire for short to another. Alas, there seems to be no problem there either but thank you for the helpful suggestion.

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Just to confirm, you've connected the power to the driver box, & the DIN cables to the motors (they are 8 pin Din cables, 4 for each motor) and the handset to the driver box ? 

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1 hour ago, Dr_Ju_ju said:

Just to confirm, you've connected the power to the driver box, & the DIN cables to the motors (they are 8 pin Din cables, 4 for each motor) and the handset to the driver box ? 

Yes all connected as you have described. In the last hour I have solved one problem but got another. I examined the motherboard with a loupe  magnifier and found surface link (or coil) L4 to have failed. This link is on the power input to the board. All other "L" components read zero ohms, so I assume them to be either Links or coils. I have replaced it with a piece of fine wire (to protect the PCB). Now I get no error message. The RA works fine but the DEC will not work at slow speed. It works at 9 but at 2, 3 or 5 the motor oscillates from side to side. Suspecting the motor I swapped the motors round. The one connected to the DEC still shows the fault. I can understand the link failing with the surge of switch on but am currently at a loss to find the new problem. It could be a problem with the motor wiring etc. or a further problem on the motherboard.

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I'd try a mains power supply. this is textbook undervoltage power supply issue. find a 13.8v - 15v power supply to try before ripping it apart again. 

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depends on how deft you are at making up \ breaking out the leads. as my first thought for the DEC motor is that one of the coils isn't being driven (these are stepper motors), hence working @ higher speeds but not the lowest....

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1 hour ago, Dr_Ju_ju said:

depends on how deft you are at making up \ breaking out the leads. as my first thought for the DEC motor is that one of the coils isn't being driven (these are stepper motors), hence working @ higher speeds but not the lowest....

Thank you for that. I didn't know that they had high and low speed coils. Yes it would appear that the low speed coil is not being driven. The motor only runs at high speed and has little starting torque, needs a little help to get going. I will try to establish which wires are to each coil and trace them through.

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1 hour ago, Anthonyexmouth said:

I'd try a mains power supply. this is textbook undervoltage power supply issue. find a 13.8v - 15v power supply to try before ripping it apart again. 

Thank you for responding. I will try to rig up a 15v supply. It has worked perfectly well in the past down as low as 10v. It usually looses it position and stops tracking if the battery voltage gets too low. At the moment it carries on tracking after I have moved the RA and DEC and the battery voltage is stable at 13.5v. 

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26 minutes ago, Dr_Ju_ju said:

No, they don't have High\Low coils....  These stepper motors have 2 identical coils and depending on how you drive them they either go forwards or backwards, see: https://en.wikipedia.org/wiki/Stepper_motor

Sorry I've not played with stepper motors before (more learning for me). Do you know of any way of measuring the signal being fed to each coil. I don't have access to an oscilloscope. From the symptoms (lack of torque, oscillation and starting when helped) as you say, it could be one coil not being driven.

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It's not easy to measure directly, 1st step though would be to measure the resistance of each coil (usually very low, couple of ohms) & if any open circuit, that would indicate an issue.... and measure from both the motor connector and the control box end....

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Problem Solved. Phew!

A big thank you to Brown Dwarf for pointing me in the right direction. Sure enough, on checking the continuity of the wiring from the controller to the DEC motor (with the motor unplugged) one wire was intermittently open circuit. A previous owner had done a repair on the DEC OUT Din Socket. It had been done very neatly with the soldered joints covered in heat shrink. Unfortunately when I stripped and rebuilt the DEC I must have disturbed this wire. It was broken but held together by the heat shrink. If you pushed it made contact. If you pulled it didn't. I re-soldered the joint and everything appears to be working fine again. Now to work on the back-lash!.

This is the first time I have posted on the forum. I have to say it's very nice to find helpful people making intelligent suggestions to find a problem.

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