Yamaha rx-v550 --- Help - diyAudio
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Old 4th December 2013, 09:03 AM   #1
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Default Yamaha rx-v550 --- Help

Hello Guys,

I have recently acquired Yamaha RX-v550 from second hand market in not working condition.I brought it home and tried to power it, the receiver was totally dead. Googled for some details, got to know that in power supply c405 cap (223k/630v) cap is usually the culprit so I got it replaced but now it powers on the display comes in for about 2-3 seconds and then shuts down.

I have down loaded the schematic of this model and on doing some probing found that there is no AC voltage coming to the small transformer T401.

I would appreciate if some one help in fixing this receiver.
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Old 4th December 2013, 06:23 PM   #2
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If powers up and then shut down there is some protection taking it down
Look and learn how to operate the service manual and the service mode while the service mode is a start up procedure with all the protections disabled ...

There is various modes that actually present the fault and also measure it IE +5v over voltage protection 20% over normal voltage bla bla bla .

beyond that there is a bunch of regulators and may one of the is faulty around the center of the amplifier and that also will trigger the protection ,

then one of the ch is out presenting excessive offset that triggers the protection ,

And finally in this line of amplifiers the problem is beyond the known capacitor and the regulators that fail quite easily tha amplifier it self and the procedure was to make a way too generic amplifier but monitor it digitally very well resulting that when the amplifier is down it usually takes the processor with and that will make the machine way too expensive to repair ...

Kind regards
Sakis
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 4th December 2013, 06:45 PM   #3
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Hi Sakis,

Thanks for your reply. I have gone through schematic and noticed that Q404(k3491) which is a switching transistor and passing on the current to D408,which is in line with the primary transformer t401, the AC voltage on t401 as per the schematic should be 88.9 at the primary and the ac voltage at the secondry should be 8.1 which is rectified though d410.

In my opinion may be the switching transistor(q404) is bad due to which i am getting 0 voltage at T401, please advice.

I can mail you the schematic .

Thanks in advance
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Old 4th December 2013, 06:51 PM   #4
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Just to let you know only the first relay clicks on power on, not the second relay before which it shuts down, during the short span of 2-3 seconds the display board lits up
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Old 1st February 2014, 06:47 PM   #5
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Hello Sakis, thanks for your pointers, got it fixed, one of the voltage regulatar 7805 was faulty, replaced it and back in business. Just wanted to complete the post so that those facing similar problem can benfit, just one more happy ending
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