Advice Needed Strange problem with no power to motor

[mossy23]

Hi, having a strange issue with my setup - Technomate TM-2300 Super, driving a Triax 88cm dish. Receiver is a VU Solo 2.

Everything was fine until this week when I went to watch something on 28.2, it seemed the dish was pointing somewhere else and was not moving. Checked the motor power LED and nothing there.
Today I ran a separate cable from the box to the motor and power came back on and everything ok.

The cable setup is as follows - 2 cables are ran from a junction box behind the TV, these go up over the ceiling and down the wall into a junction box on my kitchen wall. From there they are connected to cables that go outside underground to the dish in the back garden. There is a also a 3rd cable from the junction box to back garden

If I connect a cable over the ground from cables at the dish to cables in the kitchen, and then check for continuity with my DVM it is saying there is no break in the cables, getting about 4ohms as resistance. This is just by connecting the middle wires in the cables

Another thing I did was run a cable from the motor to the junction box in the kitchen - with this I was getting signal on BBC 1 but unable to move the motor, which I found odd.
Also there is a 3rd spare cable from kitchen to dish, I put a connector on this cable and connected to the motor. Then in the kitchen I connected this cable to the cable which feeds back to the receiver, but this did not work either......

It seems the issue is somewhere between the kitchen and the motor, anyone have any ideas where to go next?

 

[Manikm909]

Can you explain junction box ....as this has to be your issue . What is the cable run length.

 

[jeallen01]

You said that you checked the continuity of the core at 4 Ohms, but did you check the continuity of the braid as the:
- the motor forms part of a circuit consisting of the +14-18V DC from the centre core of the receiver "LNB" F-connector down the cable core, which then feeds the centre pin of one F-connector of the motor, the motor itself, and then the "-DC"/ground return back down the braid to the the outer part of the receiver LNB F connector. Any break or high resistance joint in either the core connection OR the return connection via the braid would lead to the motor not getting sufficient voltage & current for it to be able to move.
- as per the above except in respect of the connection to the above, the LNB requires may well require much less current (about 250-350mA) than the motor and might be continuing to work and produce some sort of signal but much less than normal if the return path by the braid were damaged but not actually completely broken.

Therefore, check the braid connections very carefully as there could be actual breaks/high resistance joints (due to loose F-connectors &/or corrosion due to water getting inside those connectors. There might also be actual physical damage to the cables themselves.

Unfortunately (for you!) any buried cables would definitely be prime suspects for corrosion damage!

PS: also agree with @Manikm909 about the junction box (whatever that is - pictures might well help??)

 

[a33]

Welcome to the forum, @mossy23 !


A few questions to start:

Everything was fine until this week when I went to watch something on 28.2, it seemed the dish was pointing somewhere else and was not moving.

Another thing I did was run a cable from the motor to the junction box in the kitchen - with this I was getting signal on BBC 1 but unable to move the motor, which I found odd.

1. So somehow in the meantime the motor had moved to 28E again?

2. And after this test with a run cable, did you test if you had reception on 28E with your original garden cables again? With what result?

3. Basicly, nothing of the setup has changed, since it was fine last week?

Greetz,
A33

 

[mossy23]

You said that you checked the continuity of the core at 4 Ohms, but did you check the continuity of the braid as the:
- the motor forms part of a circuit consisting of the +14-18V DC from the centre core of the receiver "LNB" F-connector down the cable core, which then feeds the centre pin of one F-connector of the motor, the motor itself, and then the "-DC"/ground return back down the braid to the the outer part of the receiver LNB F connector. Any break or high resistance joint in either the core connection OR the return connection via the braid would lead to the motor not getting sufficient voltage & current for it to be able to move.
- as per the above except in respect of the connection to the above, the LNB requires may well require much less current (about 250-350mA) than the motor and might be continuing to work and produce some sort of signal but much less than normal if the return path by the braid were damaged but not actually completely broken.

Therefore, check the braid connections very carefully as there could be actual breaks/high resistance joints (due to loose F-connectors &/or corrosion due to water getting inside those connectors. There might also be actual physical damage to the cables themselves.

Unfortunately (for you!) any buried cables would definitely be prime suspects for corrosion damage!

PS: also agree with @Manikm909 about the junction box (whatever that is - pictures might well help??)

thank you for the detailed reply! It's possible that I am not attaching the coax connectors properly with respect to the braiding, I need to have a look at this again :/
The junction box is basically just a hole in the wall where the electricians left the coax cables, so that I could then connect to the cables going down outside into the garden

 

[mossy23]

Welcome to the forum, @mossy23 !


A few questions to start:





1. So somehow in the meantime the motor had moved to 28E again?

2. And after this test with a run cable, did you test if you had reception on 28E with your original garden cables again? With what result?

3. Basicly, nothing of the setup has changed, since it was fine last week?

Greetz,
A33

Hi thanks for replying
1. I got it to move by running a direct cable from the back of the receiver to the motor
2. No, the only way I could get reception was by using a direct cable from the motor to either the receiver or to the cable in the kitchen that feeds back to the receiver (unable to power motor with this method though)
3. Nope, has been bulletproof for years

 

[mossy23]

Can you explain junction box ....as this has to be your issue . What is the cable run length.

Hi, cable run length i'm not sure, could be 30 or 40 ft ??

 

[a33]

2. No, the only way I could get reception was by using a direct cable from the motor to either the receiver or to the cable in the kitchen that feeds back to the receiver (unable to power motor with this method though)

The unability to power the motor is also with the direct (new?) cable direct between receiver and motor? That's odd.

Otherwise: testing continuity of a cable can be done by shorting the cable at one end, and measuring continuity between core and braid at the other end.
Often, as stated above, the f-connector-connection is a problem.

Greetz,
A33

 

[mossy23]

The unability to power the motor is also with the direct (new?) cable direct between receiver and motor? That's odd.

Otherwise: testing continuity of a cable can be done by shorting the cable at one end, and measuring continuity between core and braid at the other end.
Often, as stated above, the f-connector-connection is a problem.

Greetz,
A33

No, direct from receiver to motor will power the motor and give reception
Nice tip on how to test the continuity because i was wondering about that, thanks!

 

[jeallen01]

Hi thanks for replying
1. I got it to move by running a direct cable from the back of the receiver to the motor
2. No, the only way I could get reception was by using a direct cable from the motor to either the receiver or to the cable in the kitchen that feeds back to the receiver (unable to power motor with this method though)
3. Nope, has been bulletproof for years

On reflection, No 2) above might well indicate that you do actually have a faulty motor because if it won't move with that type of straightforward connection then it'll probably never move at all again! I think that we have had a few reports of faulty Tm-2300s over the last couple of years, so maybe this is another one?

IIRC, those motors are now hard to source, and so you might have to use a different make/model.

Nevertheless a full check on all the cable connections is probably still in order, if only to eliminate those as possible culprits.

 

[a33]

No, direct from receiver to motor will power the motor and give reception
Nice tip on how to test the continuity because i was wondering about that, thanks!

Good. I hope you find it is "just" an improper cable contact in an F-connector.

Otherwise, when a new cable is needed, for a motor setup I would always use a full copper coax cable (not a thin cable!).
And not too many F-barrel-connectors, to connect separate cables. Though in your case, the distance that has to be bridged is not very long.

Greetz,
A33

 

[mossy23]

Just got back to this - I got my spare cable, connected the shielding of the spare cable to the shielding of the cable that is going outside, I connected both shieldings together outside at the dish
Inside I put my DVM in series between the shielding of my spare cable and the shielding of the cable which goes down the wall out to the dish.

I got a reading of around 35 Megaohms initially, but it seemed to be slowly dropping to around 30M, then I switched off my receiver and it dropped to around 6M, then progressively to around 3M

I'm not sure if that is normal or what, nor am I sure if that means the shielding on the underground cable is fully intact? I would have expected a much lower reading, my leads are reading about 2ohms

 

[jeallen01]

In reply to your sitrep:

I think you possibly misunderstood the advice on connecting the shield and core together and so you now just have rather a "mishmash" of incorrect connections, and thus the measurements you gave are rather meaningless!

What was initially recommended relates to the originally installed cable ONLY, and so:
1) disconnect the indoor end from the receiver and the dish end from the motor - thus theoretically completely isolating the cable from anything else.
2) connect the shield and core of the cable together AT ONE END ONLY!
3) At the OTHER end of the cable, connect one DMM lead to the cable core and the other to the shield and try to measure the resistance.

The resistance should be only a very few Ohms if both the core and shield are both continuous and undamaged. However, if the resistance is high then one or other of them is damaged/broken.

If the latter is true then
1) disconnect both of the DMM leads from that original cable,
2) at the other end of the cable, disconnect the core from the shield
3) Then, using your spare cable, connect the core of that to the core of the original cable at the dish end
4) connect the other end of that core to one of the DMM leads, and connect the other DMM lead to the original cable shield
NB: you don't have to use coax cable to make the external connection, asyou could equally well (and I have in the past!), just use a piece of basis single core wiring cable to make that connection!

Then you should be able to measure the resistance of that cable loop - if very low then the original cable shield is continuous and probably OK, but if it is high then there is a break somewhere in the original cable shield.

Note also that the motor & LNB draw 30-400ma, whereas the DMM measuring current is only a very few mA, so any DMM resistance measurement may not be totally representative in this sort of situation as the motor/LNB current will result in a higher voltage drop in the cable due to the core+shield resistance. In most cases like this then that difference can probably be ignored, but always bear that in mind!

 

[mossy23]

In reply to your sitrep:

I think you possibly misunderstood the advice on connecting the shield and core together and so you now just have rather a "mishmash" of incorrect connections, and thus the measurements you gave are rather meaningless!

What was initially recommended relates to the originally installed cable ONLY, and so:
1) disconnect the indoor end from the receiver and the dish end from the motor - thus theoretically completely isolating the cable from anything else.
2) connect the shield and core of the cable together AT ONE END ONLY!
3) At the OTHER end of the cable, connect one DMM lead to the cable core and the other to the shield and try to measure the resistance.

The resistance should be only a very few Ohms if both the core and shield are both continuous and undamaged. However, if the resistance is high then one or other of them is damaged/broken.

If the latter is true then
1) disconnect both of the DMM leads from that original cable,
2) at the other end of the cable, disconnect the core from the shield
3) Then, using your spare cable, connect the core of that to the core of the original cable at the dish end
4) connect the other end of that core to one of the DMM leads, and connect the other DMM lead to the original cable shield
NB: you don't have to use coax cable to make the external connection, asyou could equally well (and I have in the past!), just use a piece of basis single core wiring cable to make that connection!

Then you should be able to measure the resistance of that cable loop - if very low then the original cable shield is continuous and probably OK, but if it is high then there is a break somewhere in the original cable shield.

Note also that the motor & LNB draw 30-400ma, whereas the DMM measuring current is only a very few mA, so any DMM resistance measurement may not be totally representative in this sort of situation as the motor/LNB current will result in a higher voltage drop in the cable due to the core+shield resistance. In most cases like this then that difference can probably be ignored, but always bear that in mind!

thanks for your reply, fwiw it's worth I think what I did is the the same as connecting shield to core but I will test this again just to make sure

what I could have done with my test cable but didn't think of it till now was to do the same test on it (shielding and core) so I would have some baseline values to compare

 

[jeallen01]

I hope I was as clear asI could be as to what, and what NOT, to do! Just keep it all as simple and possible because all that you are trying to do is to measure the resistance of a loop consisting of the core and shield of the original cable only - NOTHING else!

NB: I won't be able to read any more emails/give more advice until this evening as a I have a medical appointment to attend and then a number of "jobs" which must be done by about 6pm.

thanks for your reply, fwiw it's worth I think what I did is the the same as connecting shield to core but I will test this again just to make sure

what I could have done with my test cable but didn't think of it till now was to do the same test on it (shielding and core) so I would have some baseline values to compare

 

[mossy23]

From my testing it does appear that unfortunately my cables are damaged

My test cable gives a reading of a couple of ohms when connecting core to shield, this is what I would have expected to measure on the existing cables

thanks to anyone who posted!

 

[jeallen01]

Got back rather earlier than expected, thank goodness, and so you now have to track down where the damage is.

Obvious 1st step is a visual check of the accesible parts of the original cable, and especially at any visble F-connector joints (as mentioned somewhere above).

If that doesn't identify the location of the issue, then I would cut the cable on the house side of the buried section and individually check the now 2 sections (House-to-that-cut, and that new cut-to-dish) in the same manner as above - that should tell you more closely where the fault(s) is .

 

[a33]

I got a reading of around 35 Megaohms initially, but it seemed to be slowly dropping to around 30M, then I switched off my receiver and it dropped to around 6M, then progressively to around 3M

Might be moisture in the underground cable; alas that is worse than just an F-connector problem...

 

[jeallen01]

If the original cable was just buried in the soil then that could certainly be the problem as it was almost certainly not designed for that use - even worse if it was air-spaced stuff!
Not ever having looked at doing that for sat cables, I don't know what would be the best sort of cable to use, &/or how to best protect a "normal" type of sat cable when buried. OTOH, I'm sure that someone here can advise as I know that it has been done and described(??).