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1.2 ghz video sender components

Thread starter #1
hi
i am a student and i have a video sender that its frequency as the producer said, is 1.2ghz and its not working any more, i want to repair it but the ic part number is removed by producer, can you suggest me any part number for this sender?
 

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#2
do not try to change parts, it could be a small issue. to repair RF items you may need right equipment.
How could you confirm that it is not working? do you have the receiver for it? or you just tell based on LED?
this transmitter can not be tuned on normal TV set. it comes with a receiver.
 
Thread starter #3
do not try to change parts, it could be a small issue. to repair RF items you may need right equipment.
How could you confirm that it is not working? do you have the receiver for it? or you just tell based on LED?
this transmitter can not be tuned on normal TV set. it comes with a receiver.
yes i have receiver for it, i test voltage of the board it seems to be ok and also check for any burnt components and the current is normal all connections are like when it work i want to check these two ic but i dont know what are they
 
#4
i want to check these two ic but i dont know what are they
I do not think these ICs are having issue. Normally low power ICs would not be easily damaged. do a voltage measurement from ground to corner pins, normally one of the corner pin will be connected to +V (VDD). if you measure voltage then there could be oscillator issue. If the VDD pin is not receiving voltage then you can check the voltage regulator that looks like a transistor on the board.
 
Thread starter #5
I do not think these ICs are having issue. Normally low power ICs would not be easily damaged. do a voltage measurement from ground to corner pins, normally one of the corner pin will be connected to +V (VDD). if you measure voltage then there could be oscillator issue. If the VDD pin is not receiving voltage then you can check the voltage regulator that looks like a transistor on the board.
I did, voltage seems to be normal, fo you know what are the ic's part number
 

unclejed613

Well-Known Member
#8
most likely not a TDA8722, xtal is in the wrong area around the IC. according to the data sheet, max carrier frequency that can be programmed into the TDA8722 is 1023Mhz (all frequency select bits set to "1").
 
Thread starter #9
most likely not a TDA8722, xtal is in the wrong area around the IC. according to the data sheet, max carrier frequency that can be programmed into the TDA8722 is 1023Mhz (all frequency select bits set to "1").
I also see the crystal in schematic in datasheet is 4Mhz but in my board is 8 Mhz, i dont know dose it relate to it or not?
 

unclejed613

Well-Known Member
#11
i can look, but can't guarantee anything. the reason they shave the numbers off is so only the manufacturer knows what the IC is. sometimes you can find part numbers on the silicon if you can get a high resolution x-ray of the chip. x-rays aren't very good for ICs, so it falls in the category of "destructive testing".

EDIT: is this sending analog or digital video?
want to check these two ic but i dont know what are they
the 20-pin one is definitely the modulator, but it may also have some microcontroller functions. you have what appears to be a NVRAM chip (the one with 8 pins). the white rectangular blur with gold contacts (near the other end of the board) is likely an RF amplifier (either transistor or monolithic amp i can't tell for sure), and that could actually be what's wrong with the transmitter. it would be difficult to tell without some means of tracing the signal from the 20-pin chip to the antenna, you would need an oscope with at least 500Mhz bandwidth (a 500Mhz scope would not be accurate, but you would at least be able to see the presence of RF. or you could use a SDR radio with a pickup coil as an antenna (for 1.2Ghz, a single turn of wire would be enough to inductively couple to wires on the board carrying RF), you don't want to directly connect an SDR to the board as you would an oscope, because SDR radios can be damaged that way.
 
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