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| Yamaha RX-V771 won't power on |
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| wasedadoc:
--- Quote from: MathWizard on August 16, 2024, 04:08:48 pm ---I'm in rush ATM so I didn't check the sch, but a lot of these types of things, will have lots of powered voltage rails, when plugged in. And when you hit the power button, maybe another rail gets turned on to power all the control chips. I think on my Denon AVR, the power switch only turns on/off the 5V rail. --- End quote --- Usually it is the opposite. One low power rail is on all the time the unit is plugged in to AC mains. Pushing the on button (front panel or IR remote) activates all the other rails. |
| David_AVD:
Check that you have the 5.5V standby voltage on the output of the SMPS (power supply) board. You can measure it on connector CB377 on the video board. The PCB is marked with the 0V and 5.5V pins. Be very careful around the SMPS as it has 240V AC and 340V DC on it ready to bite you. Also be careful around the mains input connector on that video board. |
| shakalnokturn:
It could also be a half coincidence if the power to the Yamaha was completely cut when the 4A fuse blew (circuit breaker or common fuse in socket opening). A lot of Yamaha amplifiers use a capacitive dropper in the standby supply, the capacitor ages and eventually leads to the symptoms you have, it may have aged to the point where it was able to only just keep the standby going up to that point but not enough to reach sufficient voltage from a cold start. As said above check standby 5V. |
| MathWizard:
So if it was just connected to line out from the Jamo, I don't see it on the schematics Raff had, but it should be just a low-power signal, from the op-amp section. And even if the Jamo had some input signal, a line level output, shouldn't damage much of anything. Maybe some IC would not like any negative voltage from a line-out. In the Yamaha the SW-opamps are on page 115, and their mute circuits are on p117. Those mute circuits are run from +/-12V, where as I think the op-amps in the Jamo are +/-15V rails. In the Yam I see the caps around there are 50V, but they are electrolyics, and could get reverse biased, and fry. Or can some base junction in the muting circuit see too much voltage ? As for the Jamo, well I wish I had it here, I'd start with it unplugged, and probably find a few problems right away just with a DMM. |
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