Yamaha RX-V675 Repair

My approx. 5-year-old Yamaha RX-V675 receiver started playing up and I was not looking forward to a costly replacement so I decided to attempt a repair.

The symptoms of the failure was
– No sound when turning on
– After a few minutes sound would cut in then cut out with a pop sound
– The sound would stay on for longer each time
– It would take about 20 minutes before the sound would stay on
– The issue occurred on all inputs and even AirPlay so it seemed to be more on the output side internally

The fact that it took time to start working, pointed me in the direction of a dry solder joint. This is when either from a manufacturing defect or from overheating, the solder breaks away. This break is reconnected when the area heats up again through expansion.

The first step was to open the case and check the board.
There were no burn marks, corrosion or bulging capacitors on the board so once again it makes me think dry solder joint.

The system has two sections. One appears to be the digital side, the top board and the analogue amplification board below. The connections on the lower board were beefy and I thought it was unlikely to be one of those connections.

The next step was to turn the box on and go over the board with a hairdryer.
This would quickly warm the components allowing me to see which one was the likely culprit.
Having seen many chips with this sort of issue, I first focused on these.
This particular board has about 11 larger chips, going through them one by one with the hair dryer, the bottom right-hand corner the audio came on.

I was lacking a can of freeze spray, so I improvised with a snaplock bag of ice.
Placing this on the board over the area the sound cut out again after a few seconds.
Back again with the hair dryer, I managed to narrow it down to one chip.

So now I know which chip it is, it is heat related and 99% a bad solder joint.

The next step is to reflow the solder. Normally you would use a specialised heat gun to achieve this, but unfortunately, I don’t have one.
The other option is to put the board in an oven, but you risk damaging parts, melting things and the capacitors need to be removed first or they can explode.

With a infrared thermomiter I thought maybe, but unlikely I could get the hair dryer up hot enough. But I was only able to get it to around 80c, well below the required temperature.
Next, I tried my wife’s craft heat gun. This was better, but still only 110c.
I was running out of options, but then I remembered I have a Ryobi Heat Gun used for paint stripping.
This did the trick, I was able to carefully bring the temperature up to 240c keeping it there for a few seconds then let it cool down.

After waiting about 30mins it was around 20c and it was the moment of truth.
I had a few outcomes, it was totally dead, the same issue, or it worked.

The machine powered up, bam, audio!
It wasn’t dead which was the main thing.
I powered it off again and cooled it further with the ice bag to below 20c.
Powered it up again, audio!

Before putting the top back on, I added some heatsink compound and a small heatsink to the affected chip. It has obviously overheated at some stage, so I am hoping a small amount of heat dissipation will help prevent this from happening again.

The last test was to wait until the next morning. The cold mornings of the coming winter is what made this issue first apparent. Over the summer it was fine, so I am unsure when the fault actually occurred.

After a good sleep happy with my achievement, I woke up in the cold and hit the power button.
There was that short delay when it turns on that had me waiting with anticipation, it worked!

It has been about 2 weeks now and it is still going strong!


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