This Is News To Me. Stab HH100

RustySpoons

RustySpoons

Sleepy Hollow
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My Satellite Setup
50E - 30W
2x CM 1.2m Polar Mount/Jack
65E- 65W
Gibertini 1m OP100 - STAB HH100 - Inverto Black Ultra 0.2 Twin
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Dreambox DM800HD
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Thanks, RustySpoons. I will check that.

Also the collector pin of transistor Q2 seems to have been hot (it's a bit blackened). Could that part of the circuit have something to do with the burning of R20, too?

Photos of my circuit board with burnt R20 can be seen at the dutch forum: STAB HH100 onderdeeltje doorgebrand
Also the "dossier technique" of the HH100, complete with circuit diagram, is there: It's not too large to be uploaded to sat4all.com!


And another forum member has reported a motor with a defective R20 there. Is the R20 not dimensioned well in these motors? Should it have a greater resistance value, or be able to handle (dissipate) more power?

greetz,
A33
I read the post on the other forum you just linked to, when I said it's there for current limiting its to limit the power drawn from the STB, especially if there is a fault condition. The 7805 doesn't need it normally, however it can sink 1amp (Or more depending on flavor) which you do not want on your STB!
Check Q2 to see if it reads correctly on diode setting with multimeter, resistance setting will tell you if it's completely gone however but will not show if it's functioning.
When you fit the replacement R20 stand it up longer on its legs so it's off the PCB, it will get better airflow, not char the board and the legs will also help dissipate heat. No harm in going up with current capability, i.e. 1w instead of 1/2w etc (Not sure whats fitted). But I wouldn't mess around with the value.
 
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A

a33

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I'll have a look what I have lying around at about 40 ohms.
But right now I've got some nasty flu.... :(

After checking and replacing, I will check the temperatures of the components too, while attached to my STB.

Greetz,
A33
 
Channel Hopper

Channel Hopper

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I would advise installing 2 x 75 or 2 x 82 Ohm resistors in parallel (if they fit), which gives the user an indication of impending falilure of the Stab rotor when one goes open circuit down the road.
 
A

a33

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Likely it's used as a current limiter, I should imagine it's just burnt out eventually. Nothing to lose replacing it. Check the regulator hasn't gone short.
While still on the circuit board, the 7805 has about zero resistance between output and ground.
Not good, is it?
I'll have to desolder it, to check?
Or can I put a 5volt (or so) voltage to the input, and check what output voltage is there?

Q1 and Q2 seem to be no problem (BE of Q1 shows low resistance, but that is not bad because of R4 < 2 ohm?).
Though all this is a bit hard to measure, as they have sprayed the circuit board with a thin layer of I don't know what. (After repairing, should I also spray it with something?)

By the way I've "isolated" the schematic pages of the STAB HH100 rotor of the former mentioned document: see attached.

greetz,
A33
 

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Channel Hopper

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While still on the circuit board, the 7805 has about zero resistance between output and ground.
Not good, is it?
I'll have to desolder it, to check?
Or can I put a 5volt (or so) voltage to the input, and check what output voltage is there?

Q1 and Q2 seem to be no problem (BE of Q1 shows low resistance, but that is not bad because of R4 < 2 ohm?).
Though all this is a bit hard to measure, as they have sprayed the circuit board with a thin layer of I don't know what. (After repairing, should I also spray it with something?)

By the way I've "isolated" the schematic pages of the STAB HH100 rotor of the former mentioned document: see attached.

greetz,
A33
If there is only one component following on the output rail, disconnect that rather than the regulator.

You might find a diode further downstream that has gone short circuit.
 
A

a33

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If there is only one component following on the output rail, disconnect that rather than the regulator.

You might find a diode further downstream that has gone short circuit.
No, there are about 10 components connected to the 7805-output directly.

And no diode downstream. See the schematics (the 7805 is the U3).

Maybe I'll try, after desoldering the 7805, to apply an external 5V source there, to see if the rest of the circuit is functioning properly.
When also another IC is defective (e.g. LM239), repairing would be too great a task...?

Greetz,
A33
 
Channel Hopper

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The schematics didn't show the tracks under the circuit board, though the second image does show a test point, I assumed there might be a link wire before it, normal practice in PCB power design.

You could cut the track of course, then wire bridge later (or leave the full leg of a new regulator to do the same job once passed through the PCB ).
 
Terryl

Terryl

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I would remove the 7805 IC then remeasure the DC resistance at the +5 output, if still at zero ohms then there is a shorted IC or other component (capacitor) somewhere on the PCB, I would not put an external +5 power supply to the board in place of the +5 volt regulator, unless it is a current limited power supply, you may/could damage something beyond repair.
 
RustySpoons

RustySpoons

Sleepy Hollow
Messages
2,335
My Satellite Setup
50E - 30W
2x CM 1.2m Polar Mount/Jack
65E- 65W
Gibertini 1m OP100 - STAB HH100 - Inverto Black Ultra 0.2 Twin
Mutant HD51
Edision Primo IP S2
Dreambox DM800HD
Venton Unibox HD2
Sony Bravia 55" 4K
My Location
South Wales
These are all cheap jelly bean parts, just replace them and the 7805. Will cos you more in time fault finding than fitting parts.
 
A

a33

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504
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Did some testing: shortage to ground in the 5 volt line.
I did cut tracks after the L7805, and after the VCC-pin of U2, and the shortage was in the U2-part.
So I guess the shortage is in U2 itself, as was the case in a STAB motor that @Trust1 tested (see the thread in the sat4all forum).

So I'm afraid that's too difficult to repair for me! :(
Unless changing the whole circuit board; that would be doable. But they are not for sale, I believe?

greetz,
A33
 
Channel Hopper

Channel Hopper

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Send TJ a PM, he may still have the faulty Stab rotor since it was never replaced under the warranty.

Even though it shares a common failure to yours it could be useful for,stripping down to identify the second board fault and the cause.
 
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