LNB V/H Voltage

[RT-Cat]

Ted,

How did you get the replacement regulator so fast? Disappointing that it isn't working yet. I could throw out a bunch of questions if you want any more help trouble shooting it, or you could bring it up to Traverse City some time.

Radio shack had them in stock.
A few more ideas can't hurt.
If no fix, a trip could be done some day. Remember this is just a back-up receiver.

RT.

 

[Smith P.]

Well, more like Pixl's than my bad numbers.
Now I have 13.2 Volts on Vert
and 18 volts on Horz
But still will not power LNB.
Turn off LNB power and power from another source, works fine, picks up stations.
RT.

Trace is lost ... if you have see switched 13V and 18V normally ... OK, perhaps the voltage doesn't come to F-connector; try to follow the 13/18V trace to output coax; perhaps a fuse inline or small value protection resistor blew up.

 

[Pixl]

Radio shack had them in stock.
A few more ideas can't hurt.
If no fix, a trip could be done some day. Remember this is just a back-up receiver.

RT.

Ok Ted, I remember it it a back up, can't really make it worse than it is now. But bringing it back will be an interesting challenge. If you get it fixed maybe others can learn from this.
Can you set it up on the table with a short piece of coax to any lnb for loading. Cut a section of the side of the coax with a knife to expose the center conductor. All voltage measurements referenced to ground. Power up and measure the center conductor both V and H while powering the lnb. ________ Results.
Now same thing with lnb disconnected V+H_______Results.
Now measure the 3 terminals of the regulator with/without lnb, V+H.________results.
Now same set of readings on the small three terminal transistor slightly to the left of the regulator. This one to the tenth of a volt if possible. _____results.
Power down, measure the 220 ohm resistor again in circuit. (did you replace it?)

 

[Smith P.]

If he already opened the cover, he don't need additional piece of coax cable - just use the coax connector's back side ; there is exposed central wire and trace coming to it - to measure the voltages.

 

[RT-Cat]

Trace is lost ... if you have see switched 13V and 18V normally ... OK, perhaps the voltage doesn't come to F-connector; try to follow the 13/18V trace to output coax; perhaps a fuse inline or small value protection resistor blew up.

Actually, the output at the back of receiver is where I took the measurements.

Ok Ted, I remember it it a back up, can't really make it worse than it is now. But bringing it back will be an interesting challenge. If you get it fixed maybe others can learn from this.
Can you set it up on the table with a short piece of coax to any lnb for loading. Cut a section of the side of the coax with a knife to expose the center conductor. All voltage measurements referenced to ground. Power up and measure the center conductor both V and H while powering the lnb. ________ Results.
Now same thing with lnb disconnected V+H_______Results.
Now measure the 3 terminals of the regulator with/without lnb, V+H.________results.
Now same set of readings on the small three terminal transistor slightly to the left of the regulator. This one to the tenth of a volt if possible. _____results.
Power down, measure the 220 ohm resistor again in circuit. (did you replace it?)

Interesting. I will give this list a try when I dig up some time.
The resistor now reads 217 ohms with a different meter. So I did not change it.

RT.

 

[RT-Cat]

If he already opened the cover, he don't need additional piece of coax cable - just use the coax connector's back side ; there is exposed central wire and trace coming to it - to measure the voltages.

We posted at the same time.
Not really. If you look at Pixl's pictures on a different thread, that "silver box" is connected to the board. No wires.

 

[inwo]

If you have voltage until coax is connected it's more likely that is an overload or short.

Power supply will shut down or limit current to protect itself.

Check for shorted cable.

 

[Pixl]

Actually, the output at the back of receiver is where I took the measurements.

The back of the receiver is fine except I'd like a measurement with the load connected, thats why the coax with the side cut out for access to the center conductor WHILE connected to the lnb.

Interesting. I will give this list a try when I dig up some time.
The resistor now reads 217 ohms with a different meter. So I did not change it.

RT.

217 is fine. I'll bet it was the bad regulator that "in circuit" pulled it low.

I'll look for your other measurements when you have time.

 

[RT-Cat]

If you have voltage until coax is connected it's more likely that is an overload or short.

Power supply will shut down or limit current to protect itself.

Check for shorted cable.

No short. Hook up working S9 to same cables and all works just like it should.

Meow.

 

[FaT Air]

Compare resistance - output pin of regulator to LNB coax center - to that on a working receiver. Have hunch a choke in the tuner "box" may be damaged. (high R)

 

[RT-Cat]

Compare resistance - output pin of regulator to LNB coax center - to that on a working receiver. Have hunch a choke in the tuner "box" may be damaged. (high R)

Nope. Both receivers read: Left pin - 600, center - 600, right - 400 ohms.

Meow

 

[RT-Cat]

OK, here are some measurements.
Coax Center conductor with LNB: V-13.5volts H-17.5volts
Coax Center conductor with out LNB: V-15volts H-19.8volts
.
three pins on regulator. Looking at the “front” or the head of the screw that holds it to the heat sink
I will list the leads as L, C, R (as you can guess, left, center, right)
NO LNB Vert. – all in volts – L-15, C-15.5, R-21.5
NO LNB Horz. – L-11, C-11, R-15
with LNB – Vert. – L-15, C-15, R-26
with LNB – Horz. – L-20, C-21, R-26
.
The microscopic transistor:
single pin(towards the regulator) 14volts to ground
Left pin – 0 volts to ground
Right pin – 0 volts to ground
.
Unhook working receiver; connect this one to same place, “no signal” shown on screen. Power LNB from somewhere else, works great. ???


Meow.

 

[inwo]

If you have voltage on coax as you say then it is supplying current.

H/V mixed up in set-up?

 

[Pixl]

Ted,

Interesting measurements. The check on the micro transistor suggests it is bad. However the lnb voltage even when loaded tells me it should be working even with the 1.5v shift. Odd.
Do you have an identical receiver to compare the micro transistor voltages? If not I could take mine apart again and measure it.

EDIT:
One other thought. Do you have any switches in your system. If so you might temporally connect directly to one dish and see if the receiver will work now that you replaced the regulator. The micro transistor may be part of the DiSEqC insertion.

 

[RT-Cat]

Ted,

Interesting measurements. The check on the micro transistor suggests it is bad. However the lnb voltage even when loaded tells me it should be working even with the 1.5v shift. Odd.
Do you have an identical receiver to compare the micro transistor voltages? If not I could take mine apart again and measure it.

Yes, identical receiver. In fact I changed the power supplies today just to see if that might be a problem. No help. Sometime Wednesday I'll look into the good one and see what the micro transistor reads.

EDIT:
One other thought. Do you have any switches in your system. If so you might temporally connect directly to one dish and see if the receiver will work now that you replaced the regulator. The micro transistor may be part of the DiSEqC insertion.

That was the first thing I did after I replaced the regulator.

Meow.

 

[RT-Cat]

If you have voltage on coax as you say then it is supplying current.

Well, maybe. I made a "shocking" device many, many years ago and it had voltage as high as the sky but no current to speak of. Fraction of an amp.

H/V mixed up in set-up?

How would/could you do that?

Meow.

 

[inwo]

Ohms law.

The load is fixed. ie. lnb

If you have proper voltage on the coax you WILL have the proper current flowing.

Open circuit is another story. The voltage means nothing then.

If you don't believe me measure the current.

As far as how it's possible to mix up the odd/even. I have no knowledge of your equipment.

But if lnb is powered and you show no signal, what's left.
Do you have an in line meter?

 

[RT-Cat]

The load is fixed. ie. lnb

If you have proper voltage on the coax you WILL have the proper current flowing.

Not really. Lets say the LNB needs 18 volts and 1 amp to work. The power supply is putting out 18 volts, but there is something wrong and it only can supply 1/4 of an amp. The LNB can't just "make" the power supply supply the 1 amp it needs just because it is there. It will get voltage but not operate because it does not have the current it needs. That appears as what the problem is with this unit. Power the LNB from another known to work source, and the receiver works fine.

RT.

 

[Smith P.]

If you have voltage on coax as you say then it is supplying current.

Discard it. Without load the VR will supply DC to coax.

He posted enough to see the load is there:

Coax Center conductor with LNB: V-13.5volts H-17.5volts
Coax Center conductor with out LNB: V-15volts H-19.8volts

It's a voltage regulator with limited source current - see a 1.5V voltage drop with a load, the VR is not a current stabilizer. Check Ohm's law.

Usually load of Ku LNBF is 300-500 mA max. So, internal resistance of the VR is 3-5 Ohm, not bad.

"with LNB: V-13.5volts H-17.5volts" - these levels are good enough to drive LNBF if these getting into it...

Now the big question - what VDC levels are near LNBF ? Can you measure there ?

 

[inwo]

He posted enough to see the load is there:

not bad.

"with LNB: V-13.5volts H-17.5volts" - these levels are good enough to drive LNBF if these getting into it...

That's what I'm saying!

The circuit supplying the lnb is more than a voltage regulator. It will also be current limited. And have a 14/18 volt switch.

The 1.5 volt drop is normal under load.