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Need help choosing replacement transistor

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RickyZA

New Member
Hi there everyone,

Im looking for a replacement transistor for a logic board, unfortunately there was a short and it blew out the transistor, the short has been resolved though. Here is the damage. Q8002


Board Model : EAX61682903

Original Transistor Datasheet : http://pdf.datasheetcatalog.com/dat...ctronics-corporation/RT1P141C_to_RT1P141U.pdf Marked P1
No input voltage stated on first link although this one says -40v , https://www.idc-com.co.jp/search/search/Pdf/en/6/RT1P141U , my alternative DDTA114 states +10 to -40v , the PDTA114 however states only +40v, otherwise the PDTA114 is actually very very similar although im not sure if this was a typing error.

Links : DDTA114 http://pdf1.alldatasheet.com/datasheet-pdf/view/178572/DIODES/DDTA114ECA-7-F.html
PDTA114 - http://www.farnell.com/datasheets/1511866.pdf

Main Board Schematic for transistor Reference: https://www.manualslib.com/manual/1196638/Lg-32le5500.html Not the exact same model but im pretty sure they use the same transistors marked P1 which is the RT1P141C and marked exactly the same on the board as Q8002. I can also see the P marking on the transistor all though the 1 marking is burnt out.

Thank you
 

JLNY

Active Member
It seems like the DD/PDTA114 replacement that you have picked out would work. The bias resistor values are the same, and for a switching application the specific gain characteristics likely won't be important. According to the manual, the Q8002 transistor functions as a switch for switching an IC at an enable voltage of 3.5V, so the difference in voltage ratings is unlikely to matter.

The real question in my mind is whether the short that caused Q8002 to fail in the first place damaged anything else. If there is a fault somewhere else on the board that caused it to fail, then replacing it may only cause it to burn out again, or there may be other problems elsewhere on the board.
 

RickyZA

New Member
It seems like the DD/PDTA114 replacement that you have picked out would work. The bias resistor values are the same, and for a switching application the specific gain characteristics likely won't be important. According to the manual, the Q8002 transistor functions as a switch for switching an IC at an enable voltage of 3.5V, so the difference in voltage ratings is unlikely to matter.

The real question in my mind is whether the short that caused Q8002 to fail in the first place damaged anything else. If there is a fault somewhere else on the board that caused it to fail, then replacing it may only cause it to burn out again, or there may be other problems elsewhere on the board.
Hey JLNY, thank you for the reply bud, so either look good, im happy i dont have to end up importing which could take weeks.

Unfortunately what happened here is that the 20v shorted out with the PWR_ON, this was utterly a human mistake that unfortunately couldn't be avoided, so instead of that pwr on getting 3.5v it got 20v which burnt out the transistor, i hope that nothing got damaged in the process, i was thinking seeing as these transistors dont cost an arm and a leg it would be worth a try ? The power board seemed to give out the same voltages after the incident so i ruled that out as fine for now.

If you would like me to give you more detail/pictures of the power board please let me know. Really appreciate the help JLNY its been a tough one getting some so far !
 

JLNY

Active Member
Not a problem. It seems like you have already done most of the legwork finding those part numbers.

Ouch. 20V on a 3.5V line has the potential to do some major damage. Hopefully it was just that transistor, but it's possible that the input on the IC, or any other ICs running from that rail may have also been damaged. The only way to be sure would be to order some and give it a shot. As you say, the transistors are inexpensive enough that it can't hurt to try. I would double-check the PSU voltages to be sure everything is outputting as intended, but if you are sure the fault is cleared then it's probably just a question of whether any ICs got damaged.
 

RickyZA

New Member
Not a problem. It seems like you have already done most of the legwork finding those part numbers.

Ouch. 20V on a 3.5V line has the potential to do some major damage. Hopefully it was just that transistor, but it's possible that the input on the IC, or any other ICs running from that rail may have also been damaged. The only way to be sure would be to order some and give it a shot. As you say, the transistors are inexpensive enough that it can't hurt to try. I would double-check the PSU voltages to be sure everything is outputting as intended, but if you are sure the fault is cleared then it's probably just a question of whether any ICs got damaged.
Thanx JLNY, just needed help making sure they would be suitable, hopefully the board is still good to go after the replacement, i hope i havent damaged anything else, the transistor pretty much got smoked, didnt notice anything else getting damaged though. Im going to place that order for the PDTA114 and ill keep you posted. Thanks again bud
 
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