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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Update: Pioneer PRO97 powerdown problem
After verifying vertical def signal and retrace were good, looked into
the power down circuit for loss of vertical. Found a pad lifted at Q-211 collector. Read 4.5V at Vdef test pin, but nothing at collector of Q-211. Anyway power down repaired. Now, with set powered up, I get a picture, although misconverged now (mainly on the right portion of the sceen). Also noticed that when cycling through the different video inputs, the OSD font color for each changes. CH3 is green, Vid1 is green, Vid2 is green, Vid3 is red and blue (misconverged), LD is blue. Not sure if this happened after replacing the vertical deflection IC, but hoping this is normal. I was working on navigating through the convergence adjustment procedure when a resistor blew in the power supply. Also noticed the coax input doesn't give a picture (black raster) when connected to my Sencore (trying to display crosshatch). This is all for now. Will post another update when I make further progress - don't hold your breath! |
#2
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Update: Pioneer PRO97 powerdown problem
Have you changed the STK4277 yet ? Sounds like you need to.
However this is not blanking the video. You usually don't get snow without an antenna on Pioneers, but can you get a video signal ? If you can, you probably need a couple of caps in the IF module. That is common and I've seen where customers just watch it through a VCR tuner, for years even. Don't try to analyze the convergence error. Their circuit is such that you just must put in a good IC. If the IC is partially shorted, that probably caused the current failure of the power supply. IR will probably turn out to be a fusible somewhere. When you get the STK, there is a suffix, either STK4277L or SL. Whichever it is get that, otherwise installation will be more of a PITA. And the heatsink, make sure it is completely clean and apply a bead running between the mounting holes. Do not prespread it. It is important with a six channel IC that is pushed pretty hard. But do tackle the video first, otherwise you don't know if the fix worked. Thing is now you got sweep, the next thing is video. Run it with the 4277 removed if necessary, but see a picture. JURB |
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