Echostar Gregorian dish positioner problem

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#1
I have a Echostar AD300IP and a 1.2 metre SCT Highway gregorian dish. For a number of months I have had a positioning problem which has been getting worse. The feedback pulses start acting strange and speed up or stop altogether causing the dish to lose position. I have set up my dish numerous times and then it happens again.

I have looked at the motor arrangement on this dish and found it to be a simple electric motor and a few cogs. One of the cogs has a hole cut out od it and a reed sensor either side. As it spins it obviously sends pulses though the electonics and on to the receiver.

Could the sensor be the problem? I would have thought it would either work or would not work and no in between? The problem can be there one minute and not the next.

Could the receiver be the problem? I do not have a spare receiver I could try and I do not want to buy another and find the original receiver was okay and the problem was the sensor all along. It is not the wiring as I removed the motor altogeter and connected it at the receiver with a short lead and I got the same problem.

Is there some checks I could do with a multimeter at the receiver end when the dish is moving to see if I am getting the pulses. What exactly do I look for.. I have checked the 5 volt line with is okay

Thanks for any help
Darren

p.s If any one in Aberdeenshire has a spare receiver I could borrow for a couple of hours I would be extremely gratefull
 

Old Satellite

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#2
It might not only be a mechaincal problem, as the fault that you describe might also be related to that of a commom positioner electronics problem on the Echostar 3000.,

The problem involves the counting circuity , several problems have been reported from that of a faulty solder joint to a faulty de coupling capacitor , and in some cases that there is also on the power 5vdc rail a faulity regulator.

Indeed try to check all the machanics and then see if you borrow another reciever to test the installtion.


regards

Old Satellite
 

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#3
If its a fault that gets progressively worse I would check that there is no corrosion on any of the sensor wires into the motor, and no cuts in the cable

As a temporary check bring the actuator indoors for a check in front of the fireplace. Bolt a long rod to the motor and check the distances marked on the nearest wall, repeat moving back and forwards for an evening
 
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#4
I had a problem a while back with my positioner getting confused as to where the dish was. At the time I was using plain and thin 2 core cable for the motor and the same for the sensor, similar stuff to speaker cable. It turned out that the sensor cable was picking up interference from the motor cable and screwing things up. I changed the cables to 6 core, similar to telephone cable, using 2 of the cores for the sensor and doubling up the remaining 4 for the motor. Since then I have had no problems.

Cheers
 
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#5
Hi thanks for your replies. I changed out the opto coupler feedback device in the motor and the problem is still the same. I am now convinced the problem lies with the receiver. I cannot believe it could be the motor as it can work one minute and not the next.

Thae cable is good quality ribbon cable and is shielded. I removed the motor and connected two short lengths of separate cable and it was still the same so that is not the problem.

I connected my multimteter to the teminals for the M pulse and earth and the voltage is okay when it is working fine but the voltage would then suddenly drop to about a third of a volt and the pulse count would then stop.

Old satellite
could you be more specific in the location of the fault you describe. I could look and change out the decoupling capacitor and resolder the joint

thanks
Darren
 

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#6
Are you sure the 5volt rail from the Echostar is not the one used for a mechanical polariser > If so this would cut out about four seconds after operating the remote control

The software setting should be set to 'continuous' if there is a separate polariser menu, usually near the LNB DRO menus .
 

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#7
Check the underside of the power supply for the following -

Burnt areas, especially around C12. Replace this anyway (4.7uF, 50V).

Check resistor adjacent to C12 (should be low value - around 12 ohms)

Make sure all soldered joints are well soldered.

C43 (motor drive decoupling) 100mF 400V should be OK, but I replaced it anyway.

You could check the diodes around the pulse feedback circuitry (near the motor terminals) with an ohmmeter (low ohms range - no reading one way, about 50 ohms other way).
Hope this helps. Other than this, you really need a digital 'scope to check pulse counts etc.

David
 
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#8
Thanks guys

Removed the power supply board and the position of C12 was obvious as there was a burnt section of the board which stood out a mile. I checked the diodes and they did not give me the readings expected so it looks like a couple of them are goosed. The resistor adjacent to C12 did not give me any readings at all.

Unfortunately I am not very good at soldering. One or two components are just about okay but having to do quite a few is not something I would relish. Does anyone know if a new board can be purchased for the Echostar. The receiver works fine otherwise. Other than that how much would it cost to get a repair done on the board.

thanks
Darren
 
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