Need someone to look picture to say if this is normal or not [Uploaded in post]

[Omron]

Guys I have set top box which has no power on in specific case. When I insert antenna plug which has 12V on it because of dB gain device on top of antenna, device if its turned off, it will not turn on.
After I need to open the case and short + and - on ABS10 chip and after that device will turn on, without antenna plugged in, after its turned on I can plug in antenna and it will work fine, but I notice there is some extra heat inside the unit.

Is this chip okay? Rectifier bridge ABS10 JQC I don't think there should be connection like additional diode between plus and minus and apparently on my chip there is.

[stj]

yes, if you put voltage on the output in one polarity it will go through 2 diodes in series and in the other polarity it will be blocked.
and it does it twice.
so 5.66 x2 = 1.22 and then the 2 pairs are in parallel so 1.22 /2 = 511mV drop

[CapLeaker]

It may use DC on the input of the bridge rectifier. That explains the bridge rectifier getting warm. For what is the bridge rectifier then there, if there is already DC on the input of it? That’s because you can hook up DC disregarding the polarity and the rectifier will straighten out the polarity mismatch.

In reality we got to see the circuit in order to see what’s going on here and see your setup. If we talking powered amplifiers trough coax, either your hookup is wrong or you missing a DC blocker. If we talk about dish receivers, the 12v do not come from the LNB it comes from the receiver itself. Actually there is 12v and 18v and it changes the polarity of the LNB (horizontal vs vertical as an example).

Circuits need to be explained, so one can give you a proper answer.

As far as your ABS10, stj gave you a correct answer.

[Omron]

Thank you for looking up my case guys, I uploaded pictures with description, I hope it will be better and easier to understand issue now. Also Chip ABS10 is not hot, what was hot was that heater (uploaded on picture below). I hope its normal and safe to use though, don't want to catch fire or anything.. It was burning my finger when I put on it, couldn't hold it more than one second there. I wrote exact issue I have on pictures descriptions, hope someone will know why this happens, I would love to fix it and find the problem.

Board has name "JNMB1509M.R850.E168TV.VER1.1 " written on it the device is Xwave, its used basically to give DVBT2 signal from RF Antenna to TV using HDMI cable, because my TV Supports DVBT1 signal (even tho on box it told DVBT2, but no)


stj 5.66 x 2 = 1.22 can you explain how this is? I didn't fully grasp it

[truclacicr]

I think the meter is measuring the body diode of the MOSFET chopper in U1. Can you tell us the markings on U1?

When you measure the voltage drop across a pair of parallel connected diodes, it will be only slightly less than the drop for a single diode. That's because the I-V characteristic is highly non-linear.

There are 3 low voltage power supplies. Measure the voltage at each of the 4R7 coils. Also measure the voltage at the output of the SOT-89 linear regulator (U6?). The capacitors are on the output side of each supply.

The output of the SMPS transformer is filtered by the 10uH coil ("100"). Measure the voltage at that point.

[R_J]

You should not have 12V on the R.F. jack going to the receiver, you need a DC block adaptor

[truclacicr]

This is a typical masthead amplifier setup.

http://sm0vpo.altervista.org/antennas/preamp-0.htm

[stj]

none of this makes any sense,
DVB-T is RF, the best way to downfeed from the roof is with satellite cable such as CT100,
you cant use HDMI and it's not a good idea to use ethernet cable either.
if you have an amplifier in the roof, i think you should try without it - they often dont help with DVB-T signals

[Omron]

This is DVB-T2 signal, my antenna is supposed to have this amplifier on it, without it it doesn't catch any channel (pictures below)

My neighbour have exactly same setup with 13DC volts going into RF antenna cable, no issues at all, and on few other houses too. I have faulty set-top-box unit.

@truciacicr "I think the meter is measuring the body diode of the MOSFET chopper in U1. Can you tell us the markings on U1? There are 3 low voltage power supplies. Measure the voltage at each of the 4R7 coils. Also measure the voltage at the output of the SOT-89 linear regulator (U6?). The capacitors are on the output side of each supply. The output of the SMPS transformer is filtered by the 10uH coil ("100"). Measure the voltage at that point."

I sure can, just you need to tell me exactly what to do? Are markings Ohm resistance? And what to check with multimeter can you make screenshoot?

stj I use hdmi cable to connect set-top-box to TV so I can get picture

[stj]

DVB-T & DVB-T² are the same frequencies - just different data rates to allow for so-called HD resolutions.
is still just RF usually in the 400-700MHz frequency range

[truclacicr]

Can you show us the power supply for your masthead amp? Is it possible that you have switched the Antenna and RF Out connections???

I would have thought that the tuner in your STB would have a DC blocking capacitor, but perhaps not???

[truclacicr]

none of this makes any sense,
DVB-T is RF, the best way to downfeed from the roof is with satellite cable such as CT100,
you cant use HDMI and it's not a good idea to use ethernet cable either.
if you have an amplifier in the roof, i think you should try without it - they often dont help with DVB-T signals

I think the OP has an amplifier on the antenna. This antenna is powered by a power supply, mounted either in the roof, or plugged into a wall outlet. The output socket of the PS connects to the RF input of the STB tuner via 75 ohm coax. The STB decodes HDTV channels, down-converts them, and feeds the content to the SDTV via HDMI.

There should be a blocking capacitor in the RF out of the PS.

[Omron]

I have two TV devices connected on this antenna, on both it works perfectly only issue is that this set-top-box is not listening when you want to turn it ON/OFF with antenna inside, you need to switch it on while everything is unplugged, after that you insert antenna cable and it will work fine yeah, but if you power it off with antenna cable inside, it will just turn off and not turn on again, until you check ABS10 chip with multimeter like in first picture, then somehow it heavenly unstuck itself and you can turn device on while antenna rf cable is not plugged in, and it will work, until process is repeated again, if its turned off while antenna is inside, it will not work again and need to re-do everything from beginning, its usable not ideal but usable device.
I use amplifier in wall socket, and it works fine on other TV just this set-top-box is not working properly...

[truclacicr]

https://rozetka.com.ua/388889691/p388889691/

You can see a small DC blocking capacitor in this photo:

https://content2.rozetka.com.ua/good.../353514239.jpg
https://content1.rozetka.com.ua/good.../353514228.jpg

[Omron]

Gonna take picture and post it tomorrow since its ultra late here atm

[Omron]

Here it is, I don't see that DC blocking capacitor