USALS Motors: The Device from Hell

[cyberham]

USALS motors: Most have "enjoyed" these devices at one time or another.

My current headache is caused by a Pansat PM900 motor. I got this motor free used. I have no idea of its history. It looks in reasonably good physical condition with no rust. It moves according to USALS commands sent to it. It just doesn't do so reliably. In fact, it mostly moves to one extreme or the other extreme. Once it starts heading to an extreme end, there's nothing one can do to stop or divert it. Once in a while, it goes to the satellite you tell it to go to.

I am using only USALS commands to keep things simple. I find using diseqc commands to move the motor to a stored satellite location is another level of difficulty.

Measured voltage at the motor with no load is 18.8 volts on a horizontal command. Very reasonable for the long 100+ foot RG6 I'm using. I am using a similar cable on an SG2100 motor without a problem.

I thought maybe my latitude/longitude was entered wrong or the data had been corrupted. So I've reentered the data without a change in operation. I even tried entering "South" instead of "North" for the latitude in case there was a programming error in the software just in case. That didn't help.

I thought maybe the 1.2m dish was too much of a burden. So I swapped for a 41" metal dish. I even replaced the Invacom LNB with a lighter LNB. No change. I can't find much info online. If they were popular, it was likely before the Internet was invented.

Pressing the physical switches on the motor does cause the motor to move west or east depending which switch you press. So physically it seems fine. The motor just seems to get mixed up about what to do when you send it commands. I don't see a way to reset the motor as you can with the SG2100. I have the original printed manual for the PM900, which is actually quite good in the old style of instruction manuals, but it isn't helping.

I've used both a GT Media V7S5X and an Edision Mio+ receiver. No difference in operation of the motor.

Any ideas?

 

[primestar31]

Any ideas?

That's a VERY OLD motor, and it's only good for about 100 degrees or arc, if I remember. Is there some sort of "factory reset" mode for that? I doubt you can even find an online manual for it anymore.

 

[cyberham]

I'd be happy with 50 degrees of movement. From 129W to 87W only needs 51 degrees on the motor. I have the original paper manual but I don't see mention of a reset procedure. I may dig out my Openbox S9 (built like a tank) just to see if it will operate the motor differently. Maybe the motor needs a lot of current when it operates.

 

[lost_mesa]

I feel your pain. I had a different brand of motor that keep running away into one limit or the other. I ended up mounting my 1.2m Ku dish on an old C Band mount and actuator. It worked flawlessly for years.

 

[FTA4PA]

I have never used a Pansat motor. I do have our Stab HH100 though. It has been running great for over a decade now. Only issue I have had was when I had damaged coax twice (animals ). I hope you can get it sorted out.

 

[one_db_compression]

I'd be happy with 50 degrees of movement. From 129W to 87W only needs 51 degrees on the motor. I have the original paper manual but I don't see mention of a reset procedure. I may dig out my Openbox S9 (built like a tank) just to see if it will operate the motor differently. Maybe the motor needs a lot of current when it operates.

The DiSEqC Bus Functional Specification - version 4.2 from February 1998 - shows a bus current rating of 500 mA, even when stalled.

That you can drive the motor, even to incorrect positions, suggests that the motor and the gearing is in working condition. That it misses the set points and that the position buttons are non-functional suggests that the motor's position encoder and/or the microcontroller's input lines may have issues.

If it were me and my cost base was zero, I would be looking to crack open the enclosure to take a look for corroded contacts, etc.

Your mileage may vary. Use if useful.

 

[cyberham]

That maximum current isn't so high. I can't get away from the feeling that even reducing the weight as I have, the motors lack of torque could be the problem. It seems wimpy for lack of a better technical term. It moves slow and seems to have no get-up-and-go.

The physical buttons on the motor (position buttons?) do work. They move the dish left and right as they should. I likely will open it up, not that I can likely fix it, but it's probably interesting to see its insides.

I have an SG2100 in the wings the seller is offering for CDN$10 so I may get it. I already have a good working SG2100 pushing my main dish so this is all just to make use of my spare dish.

 

[a33]

Any ideas?

It might be, that the USALS/diseqc command is received in a distorted manner.
Did you try the motor with a short cable?

Otherwise, checking the inside of the motor (if possible) would also be my way.

If the GotoNn commands do work OK, that would be a possibility also?
Use USALS (when it has a moment of correct working) to find a satellite, and then Store it under a position number...?

Greetz,
A33

 

[jorgek]

When you open up the motor, check that the screws that secure the opto-isolator are tight.
The screws became loose on my HH90 causing erratic movement.

 

[cyberham]

...Did you try the motor with a short cable?

I pulled the motor in and set it up on my workbench with a 5-foot cable between the motor and receiver. Worked like a charm! I gained new respect for it. It's as slow as a turtle, but it's reliable in this environment as I commanded it to go back and forth between satellite positions. While in this environment, I took the time to USALS-motor to each main satellite position and program that position into a motor memory so I could try using it without USALS after re-installing.

There is a note on a label on the motor that says you should use a cable no longer than 25 metres. My cable to the dish consists of two old joined RG6 and total length is a lot longer than 25m. The label also says it was Made in Slovenia.

The manual has a sentence: "When the motor does not operate correctly, the first step to be taken is resetting the motor, i.e. sending it to the selected outermost (HOME) point..."

The above may explain why the motor goes to its extreme eastern limit then returns when sending a Goto Reference command.

So I re-installed the motor outside again with a dish. It is unreliable again. One thing I realized is that on my workbench I had the motor sitting with its mast stub upward vertically for convenience. I think some Stabs are installed like this. But outside I am installing the motor with its mast stub pointing downward toward the ground. Its instruction manual shows photos of the motor like this (downward-pointing stub).

Would this make a difference?

 

[FTA4PA]

One thing I realized is that on my workbench I had the motor sitting with its mast stub upward vertically for convenience. I think some Stabs are installed like this.

Yes, my Stab HH100 shaft faces up in the installed position.

I also have a coax run of around 120 ft without issue. Not sure why your Pansat motor would have a shorter coax run limitation.

 

[Titanium]

Switches, corroded connectors and crappy coax are the bane of modulated 22KHz signaling (especially when controlling with 13Vdc (vertical transponder selected). You would likely experience much improved reliability using copper core, quad shield, RG11 with minimal connectors or switches in-line.

Do you have a scope to measure the 22KHz signal amplitude? DiSEqC / USALS spec is approx. 650mV. Some devices are usable down to 400mV, but once the signal is too weak, any type of interference will corrupt the control and return signals.

 

[cyberham]

The good news is I have no diseqc switches in line for this setup. Also, I'm using only horizontal transponders during testing so 19 volts. The cable goes straight from the receiver to the motor to LNB. I don't have a scope of any kind so I will have to work smart instead.

I will take receiver / test TV to the dish and confirm the motor will move the load of the dish I'm using with a short 5-foot cable as I did on my workbench. If this test passes, then I can roll out much better RG-8 cable that I have for the 125-foot run. Though it's 50 ohms, I don't think that should matter in this case. I may need to get adapters to be compatible with the F connectors but I may have those already if I dig around.

With all the stuff I already have, I'd rather not buy expensive new cable right now for this redundant system. Where I live there is no RG-8 or RG-11 to buy locally anyway. I already have a working Ku diseqc motor on my other Ku dish that works fine.

 

[a33]

But outside I am installing the motor with its mast stub pointing downward toward the ground.
...
Would this make a difference?

The way I see it, it is more an electronic issue than something physical.
So I don't think it would make a differencve.

Greetz,
A33

 

[cyberham]

I tried both the Edision and the V7S5X receivers sitting beside the dish. The dish was flopped over at the western extreme. Neither receiver moved the dish. I could hear the relays clicking in the motor and see the LED indicator on the motor receiving signals from the receivers. But zero movement. I even tried assisting by lifting much of the weight of the dish assembly off the motor. Still no movement. I pressed the physical buttons on the motor which previously had moved the dish but they did nothing.

Maybe the dish was then wedged at the limit from the previous trip down to the limit. I removed the entire dish. Still no movement possible by the motor. Because it was easy, I turned the motor upside down to allow the stub to point upwards. No movement.

I've brought the motor back to my workbench as I did the other day. No movement. Maybe I broke it!

Time to open the motor and start exploring.

 

[cyberham]

No ah-ha moments after opening. Actually, it looks in good condition with no evidence of wear or bug infestation.

 

[a33]

I pressed the physical buttons on the motor which previously had moved the dish but they did nothing.

So, as the relays are clicking: is the voltage reaching the motor?
If yes, the problem is in the motor.
If no, are the relays in fact switching (even though you hear them clicking)?
(I'm not sure if a stuck relay is still able to give a clicking sound?)

I hope you find the cause!

 

[FTA4PA]

Sorry to hear that nothing appears to be amiss. Will definitely make it harder to figure out the problem.

 

[jorgek]

I'm not an expert, but the long questionable lack of quality coax runs would be something that I would avoid!

 

[cyberham]

I'm not an expert, but the long questionable lack of quality coax runs would be something that I would avoid!

Today I had my receiver right beside the dish with a 5' length of RG6 and the motor wouldn't move. So the long coax issue is resolved. It's not the problem.