Yamaha rx-v471 wont turn on After power surge - Page 1
Forum section: electronics / repair

author: mtr18103
author_rank: Newbie
timestamp: December 19, 2017, 02:07:14 pm
content: Hello,I had a power surge last month and lost a 55 Inch TV, Cable boxes, Router, Yamaha RX-V471 rec, and DVD Player.I want to repair the Yamaha Home theater receiver. Here is what I know;I have 3.3 standby Voltage and red LED next to power button is on.I have 5.5 volts On PS board and going out to other boards.Both Fuses on PS board are OK.Relay does not click or turn on when I press the Power button.I tried rest and diag mode by holding Info + tone control and Power on. LED just blinks once.The relay has AC 120v on input side and nothing on the output side so there is no AC to the main transformer.The control wires to the relay have 5.5 volts on both contacts, I assume one of them needs to go active low to enable the relay. I am assuming this would be the PowrON signal from the small power on board up front.I see a cable with a Blue wire from this larger board and the blue wire says POWON on the connecting board. The main board it looks like to me.This signal does not change state when I press power it is always high (5.5) volts like the contacts to the relay. Id the Main board seeing an issue and thus not giving the POWON signal?I do not see any obvious burn spots or blown capacitors.What am I missing? What is preventing the Power ON signal from going low?Any suggestions would be much appreciated if only for a learning experience.

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 19, 2017, 06:30:14 pm
content: For Diagnostic mode, press Info + Tone Control, then while holding them, press Power.This works for all but a hard short, like a blown amp channel or shorted filter cap, provided the microprocessor is OK or not otherwise inhibited.Here is the service manual.http://elektrotanya.com/?q=showresult&what=Yamaha%20RX-V471&kategoria=&kat2=all

author: mtr18103
author_rank: Newbie
timestamp: December 20, 2017, 01:03:07 am
content: The only thing that happens when I do this is that the red LED blinks once.Can I assume the main board is blown.

author: SMdude
author_rank: Frequent Contributor
timestamp: December 20, 2017, 03:00:33 am
content: Check on page 24, this says how to disable protection mode.The board is not fried, just some component(s).Cheers

author: mzacharias
author_rank: Frequent Contributor
timestamp: December 20, 2017, 12:11:03 pm
content: Quote from: mtr18103 on December 20, 2017, 01:03:07 amI would say try again, making sure to hold the first two, then pressing Power. If it still does not work, check for shorted output transistors or a short to (chassis) ground involving the main filter capacitors (this can be checked at the collectors of the PNP and NPN outputs) also check the main bridge rectifier for shorts.

author: mtr18103
author_rank: Newbie
timestamp: December 20, 2017, 06:57:44 pm
content: Thanks all, I will try this tomorrow and post what I find!

author: mtr18103
author_rank: Newbie
timestamp: December 21, 2017, 04:52:17 pm
content: NO diagnostics will come up at all even with trying to bypass protection. The only thing that happens is the led toggles on and off. Knowing I was hit by lightning, this may be a lost cause.Again only 5.5 and 3.3 volts are present. I will look for directs shorts that may be causing this as you suggested.