Yamaha RX-V540 Receiver won't turn on and stay on

[MarkA]

Hi Guys! new to the forum so please bear with me.

I bought a used Yamaha RX-v540 a/v receiver and made the mistake of not turning it on before leaving the person's place I collected it from...yes i know take it back right? well no, I like a challenge.

I watched blog #379 and it was great to see how David fixed his Yamaha and the feeling of achievement I can imagine.

Mine powers up, but when you press the standby power button to turn it on the relay clicks but then switches off meaning the protection circuit has been activated. I started her up in diagnostic mode and found DC % in range however PS % was not (1%).

Any ideas? i'm not overly tech savy as I didn't pay attention at school during tech college but I can follow instructions using my MSMD strategy...Monkey See Monkey Do....

[David_AVD]

PM me if you need the service manual for it.

[MarkA]

Thanks for the offer David, I found it online :-)

was just hoping someone has had the same issue and it was say 'capacitor a', rather than having to go through all the circuits with a MM...my wife would kill me

[tekfan]

This might be completely irrelevant to your situation but here goes my recent experience with a receiver:

I repaired a similar Yamaha RX-V396 receiver several weeks ago. Someone spilled water on it while it was powered up. It blew 2 of the 5 power amplifier channels. After replacing the blown transistors and resistors it still didn't power up. I checked the protection voltages the MCU receives. It was definitely receiving the wrong voltages but all the other components measured OK, the supply voltages were all in spec and powering the power amp board from an external supply provided the correct bias currents for each channel. All of the protection signal voltages (overcurrent, power supply, DC offset) were not within spec. Some were negative but should have been positive. There's no possibility of the overcurrent protection signal to be negative since it is derived from the positive power amplifier supply and not in any way connected to the negative supply. I disconnected the protection signals and found that the MCU was outputting some voltages of it own. The protection signal inputs are supposed to be high impedance A/D inputs. It was sourcing a few 10mA from the inputs!!! The MCU is supplied with positive and negative voltage so that's probably why one of the protection input pins had negative voltage on it. Probably an internal breakdown or something. I connected a voltage source to each one of the inputs to force the voltages to the normal voltages the MCU receives when the amplifier is working correctly. These voltages are listed in the service manual. Lo and behold the amplifier turned on and remained on. If one of the voltages was removed it then went into protection mode and switched off. Looks like the A/D is still working correctly but the leakage path is somewhere else inside the chip.

It looks like the MCU inputs are almost directly connected to the amplifier outputs and the power amp supply voltages via only a couple of small 1/8 watt resistors. The water probably created a leakage path across the resistors and fried something inside the MCU and caused it to actually output voltage from its inputs. Not at all a robust design. After a few hours of the amplifier being fooled into thinking that the protection voltages are OK the MCU died completely. The amplifier turned on but it only displayed gibberish on the VFD and the buttons didn't respond.

I've read on a few other forums and it seems that the MCU is really the weak point in most Yamaha receivers.

I hope you get yours running. Hopefully the MCU is still fine.

[MarkA]

Thanks Tekfan for your reply below, i'm not convinced its an issue with any of the chipsets because I can bypass protection mode and all functions display under 'sleep' and I can run through the diagnostics without an issue. you would think if it was an issue with one of the chips then protection bypass wouldnt work either. I have found a few interesting threads around the traps and on youtube, including this one;

[mzacharias]

To start with, in diagnostic (protection cancel) mode, check the output of the various voltage regulators.
The manual gives a range of acceptable values for the PS line.
Generally, take 3.3 (volts) and divide by 255. Store this value in calculator memory.
Multiply this by the value shown in the diagnostics.
The resulting number, 1.8 volts for example, is the approximate voltage seen by the microprocessor for that Protect line.
If the PS line is 0 or 1, try doing a reset using the preset/reserve option toward the end of the diagnostic menu. I have seen several units with non-specific failures of the PS sensing appear to be fixed this way. Theoretically, the only way you could get a 0 or a 1 for the PS line is if ALL the voltages for that summing network have disappeared. This is unlikely but possible with a loose plug or maybe falsely triggered by a power surge or some such.

If there is some mid-range out of spec value, often you can guess which power supply line is low or missing. If the value is HIGH for example, a -15 volt regulator could be bad. If the PS value is LOW, you might be missing a +15 or +5 volt source, and so on.

[David_AVD]

Yeah, missing rails (bad regulators) and cracked joints can cause a multitude of problems.

[MarkA]

Thanks guys appreciate your help/feedback.

bit of an update for you, when I remove the other end of the cable running from power unit to one of the boards it powers on and stays on no problems... (sorry don't know the technical names).

attached is a pic, i've circled in red the plug I can remove to get it working...the only thing is it looks like a rather important board so don't want to do that as a fix....

[David_AVD]

It looks like that plug is the power feed (from the transformer) for the surround channels.  Quite important !

So you may have a fault on the surround channel board.

[mzacharias]

It looks like that plug is the power feed (from the transformer) for the surround channels.  Quite important !

So you may have a fault on the surround channel board.

The plug also supplies power for the various voltage regulators seen on the left side of the board.

Most Yamaha models have a protection "cancel" feature which allows the receiver to stay powered ON for troubleshooting, except with respect to a high-current shut-down, like a shorted amp channel or the like.

When firing it up in diagnostic mode, just keep the buttons depressed for an extra 2 or 3 seconds - the receiver should stay on.

Then you can check the output of the regulators - my guess is this is the root of the problem.

[wagon]

A very common fault on Yamaha receivers is a 22nF cap on the little standby board.... a very common fault for 'dead' symptoms.  Obviously, it's not the cause in this case, but it's good to keep in mind for next time.

[cozza]

Hi, one of these just landed on my bench, with the same symptoms. Fault turned out to be a bad NJM7805FA regulator, which was showing 0.7 volts on the +5VD2 output. The regulator tested ok when supplied externally, but the output fell under moderate load.

In diag mode, the display read PS: PRT 21%

IC406 in this case. Hope yours is similarly easy to repair.

[ysonmezer]

I use a Yamaha RX-V659 receiver. I had previously burned the capacitor on the power board 22nf 630v. I changed it with 22nf 1000v so that it would burn again. The device recently made a power failure. This condenser series had a 220k resistor burned. I changed but the device did not work. These two components are attached to the series burnt surface mount 10v zener. I changed and worked.[/img]