DG380 Power Supply Mod

I installed a 1.2 meter dish on a DG380 dish mover several years ago. This system has worked fairly well, but has always had problems moving at the low end of the arc. Recently, the DG380 has been having a lot of moving issues. It is possible that I have lost current to the motor for unknown reasons. Now seems to be as good of a time as any to modify the DG380 and try to solve the dish moving issues.

Sadoun Satellite sold the DG380 around 10 years ago. Sadoun originally had specs. showing the DG380 rated for a maximum of 1 meter dish diameter, but later changed the specs for unknown reasons.The DG380 is a fast dish mover on paper, but there is only a small amount of energy from a fta receiver to drive it. When you increase speed, you lose the ability to pull the 1.2 dish out of low angles. My thinking is if more energy were available, then the dish would pull out of low angles and have a respectable speed.

As past experience, the satellite positioner had to be modified for my c band dish because the stock positioner did not supply enough energy to move it properly. The positioner for my c band dish has ran for around a year without needing any count adjustments or having any problems. I will attempt to do the same thing with the DG380 and the Geosat 1.2 meter dish. I like stuff that runs a long time without needing constant attention or adjustments.

A controller that is inside the DG380 is similar to that of a c band positioner. Gbox, Vbox, ASC1...etc all have similar parts. To modify the c band positioner, the power supply to drive the actuator was removed, and replaced with something that was capable of supplying the power needed to properly move the dish. Why not do something similar to the DG380?

To do electronic modifications properly, a set of tools that are designed to work on small electronic parts is needed. I no longer have such a set of tools, so a soldering iron that is too big will have to do. A look at the circuit board shows that not much work is needed. Some more thought needs to be put into it, but I will most likely remove the two motor relays, attach two wires to the power side of the relays, then install the relays back onto the board. (This will be done twice because there 2 relays, one for each direction.)

Now that an idea of what to do has been found, what about the power supply? The DG380 is designed to operate with voltages in the 12 to 21 volt range. My guess is the motor is actually a 24 volt dc motor, so I will probably drive it with 24 volts. My guess is even if the motor is rated at 21 volts, then it should last a while at 24 volts. We will see...

The DG380 has been disassembled, and the motor board has been removed. Again, my idea is to lift both motor relays up, attach wires to the power side of the relays, then set the relays back down. Doing this would separate my power supply from the power that is in the coax which is connected to the DG380. This is not going to be a pretty fix because I do not have the tools to do it right. But I think I can make it work... The word "Butcher" comes to mind.


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Overall, I think this was a well designed dish mover. It will be interesting to see how it holds up to being butchered and adding extra power.
Some of the ku dish motors were nothing but junk. They were made out of the cheapest parts and had plastic or nylon gears in them. I think the DG380 will handle the mod of 24 volts @ 2 amps. We will see...

DG380 relay specs:
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Manufacturer SHORI ELECTRIC
Type of relay electromagnetic
Variant subminiature
Mounting PCB
Contacts configuration SPDT
Switched voltage max. 120 V AC
Switched voltage max. 24 V DC
AC load rating @R* 1A / 120V AC
DC load rating @R** 2A / 24V DC
Contact resistance 100 mΩ
Term. pitch 2.54 mm
Electrical life 100000 cycles
Mechanical durability 10000000 cycles
Series S2
Contact current max. 3 A
Weight 3.5 g
Body dimensions 15.7x10.7x11.3 mm
Operating temperature -25...50°C

Some fta receivers may produce around 20-21 volts on the Horizontal polarity. Relays are usually rated at a higher voltage than what is used or needed. My guess is the DG380 motor is rated for 24 volts. If I am wrong about that then this experiment may be short lived due to motor failure. It would be nice if I could find some motor specs. There are no markings or id marks on the motor that I can see.

Remember that the DC voltage needed for the LNB passes through the motor first, so when you do your mods be sure to pass this DC voltage through to the LNB connection.

As to the motor, you can do a DC resistance measurement on the motor winding's, this will give you a resistance measurement, then you know the DC voltage requirements,(12 to 21 volts DC) then using ohms law you can find out the DC current rating of the motor.

I= V/R, or I (Current), equals V (Voltage) divided by R (Resistance)

Here is a link to an online ohms law calculator.....

Code:

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https://ohmslawcalculator.com/ohms-law-calculator

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I appreciate the Good Information Terryl.

The motor relays have voltage on one side of the relay at all times when a powered fta receiver is connected to the motor. Raising the relay up and disconnecting the powered relay pins from the circuit board will also disconnect the fta receiver voltage from the motor. So the idea is to raise the power relay pins up, and connect the new power supply to them. Doing it this way allows 24 volts to the motor without bothering or disturbing the diseqc commands and voltage(s) that the motor circuits need from the receiver.

A detailed explanation on how to determine unknown dc motor voltage can be found in the link.
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Just out of curiosity, how did the modification go?
I'm frankly amazed that my very old SG2100 still works, given what I've tried to make it do. I've been looking at upgrading some things, and DG380s seem to have a decent reputation from what i've read, which isn't a lot for that model.
It seems virtually impossible to find an actual STAB other than the -90 or -100, and I have a 1.2m dish that occasionally has some heavy kludges attached to it like a C/Ku offset LNBF.

I had to get some new relays. This project should continue soon. Thanks.