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WG D9400 Red slowly got brighter, now full brightness despite red gain set to 0
lilshawn:
it is basically an obsoleted part since you'd really only use something like that for CRT's.
off the top of my head i don't recall the last place we ordered from.
EDIT: just had a lookup in a cross reference, if you can't find a 2SC2682, the 2SC2690 looks to be basically the same transistor but it can carry 2 amps instead of 1 amp which should be okay. it shouldn't change the operating characteristics much... if any. mouser has some on semiconductor branded KSC2690AYSTU parts that SHOULD work okay. it's the same family of transistors as the original, just higher current rating. i'd double check the datasheets between the original and the proposed replacement to be sure it's switching speed is sufficient and the turn on voltage is the same or similar.
the 2sc4001 might work as well. hard to tell without really digging into it.
yatzr:
I ended up getting some exact replacements from utsource.net. I replaced Q812 SC682 and Q811 PH2369 and still had the super bright red. I also tried replacing the LM1269 again (I had put a socket there last time, just in case) and no change. Then I went ahead and replaced Q813 SD1609, Q814 SB1109, and Q815 BF423 since I had ordered replacements of those as well (simply forgot to order BF422 for Q816). All that, and still have the super bright red. Not sure where to start looking next...
yatzr:
I started poking around with an oscilloscope on the neck board to compare signal levels at various spots between red and the other two. Eventually figured out that R836 had failed open :o. I replaced it and voila, perfect picture again!
jayleone:
--- Quote from: yatzr on December 05, 2020, 11:40:29 pm ---I started poking around with an oscilloscope on the neck board to compare signal levels at various spots between red and the other two. Eventually figured out that R836 had failed open :o. I replaced it and voila, perfect picture again!
--- End quote ---
I had the exact same issue with my D9400. Thanks for following through and posting the solution; you saved me countless hours of time! :applaud: