Sony STR-D990 AV Receiver.....Background Lights Are Out

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Old 03-08-14, 03:29 PM
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Sony STR-D990 AV Receiver.....Background Lights Are Out

I have an older Sony AV Receiver #STR-D990 that I bought in 1992 and still works great. The only problem is that after the machine has been warmed up for 15 minutes all the background lights go off. All systems still work fine......no issues with sound etc.but I can't see station call letters or any settings. Sometimes a smack on the side of the cabinet will lite it up again but not for long. What I have read indicates either a faulty fuse or a poor soldered connection. If I do pop the lid off can someone point me in the right direction as to what to look for?

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Old 03-08-14, 06:43 PM
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I would look for a loose wire. Follow the wires from the lights. Touch them one at a time.
 
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Old 03-08-14, 07:09 PM
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Welcome to the forums.

That unit uses a fluorescent display..... no replaceable lamps or fuse for it. You can check the solder connections to the display itself. There is also a transistor, Q-853, that is the 30 volt power supply. That transistor may need to be resoldered.
 
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Old 03-09-14, 10:20 AM
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Thanks for the welcome. I was able to find a PDF of the STR-D990 Service Manual online and looking thru the schematics I noticed in the Semiconductor Location Index that only Q-850 & Q-851 are identified. I was able to locate the Fluorescent Display easily but I cannot find a Transistor marked Q-853. Could you possibly narrow my search a bit.
Thanks for the help!

Ted
 
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Old 03-09-14, 10:23 AM
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Look for the transistor that generates the 30volts.

You can PM me the link to the pdf and I'll look it up further.
 
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Old 03-09-14, 09:51 PM
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I captured the circuit out of the pdf. You need to check it and for 30 volts at display on FL1 and FL2.

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