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Post by jeremy on Apr 24, 2015 8:50:26 GMT -5
I't got a mint RX-V377 AVR here that I bought for pretty much nadda, the only thing wrong with it is the typical Yamaha "No power at all" issue. Everything looks like new inside, and the fuse checked out ok and AC is getting to the mainboard.
So I tried the usual "Straight, Tone, Power" reset to get it to come back on but nothing happens at all, there isn't a single relay click out of the unit whatsoever.
As per the user manual (since the service manual is unobtanium) if the AVR has went into protection 3 times or more then power on is disabled, and "To contact your Yamaha Dealer". I'm guessing the previous owner had shotty speaker wire or bad speakers connected to it and that's what caused it to protect itself. I just cannot find anything inside the unit that is damaged, and I'm betting its some sort of reset since that's what the main issue was on a few other Yamahas I bought.
I seek your great wisdom Oh MasterTech  lol |
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Post by mastertech on Apr 24, 2015 9:45:18 GMT -5
That button sequence should be valid. It wasvalid for units just before this model. But, I don't have this specific manual either but I still think it is valid.
Don't forget, bad buttons, no power to buttons, bad connections from buttons to processor. Any of these could cause no protect release, and no power up even if all is normal.
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Post by jeremy on Apr 27, 2015 13:13:39 GMT -5
MT sorry I didn't get back to you on this, looked it over, and the Standby PCB is what appears to be at fault, it's identical to the RX-V373 standby board so you should be able to follow it in the service manual. Connection CB151 voltages read Pin 1 has 15.4vdc+, pin 2 has 0vdc+, 3 9.8vdc +, 4 has 0vdc (gnd). I'm suspecting Q1501 but not sure. Also I'm curious as to why the voltage is all over the place compared to the schematic?
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Post by jeremy on Apr 27, 2015 18:02:24 GMT -5
Ok, ignore my last post I got it to come on with the reset code, and it displays DC PRT: 000L and then shuts down. I can turn it on 2 more times after that (for a total of 3 power ons and 3 protection shutdowns) and have to do the reset again to get it to power on. Something in the left channel? Assuming front left? |
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Post by mastertech on Apr 27, 2015 20:06:38 GMT -5
Ok, ignore my last post I got it to come on with the reset code, and it displays DC PRT: 000L and then shuts down. I can turn it on 2 more times after that (for a total of 3 power ons and 3 protection shutdowns) and have to do the reset again to get it to power on. Something in the left channel? Assuming front left? That should mean that the receiver is going into DC protect mode because the DC of the power amp is low, or zero voltage. It has nothing to do with indicating a left channel problem. |
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Post by jeremy on Apr 28, 2015 12:06:08 GMT -5
Gotcha, so, I checked the power supply and the power amplifier out with the DMM, I can't find anything wrong with the board, so where would you suggest that I start first?
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Post by mastertech on Apr 28, 2015 14:23:01 GMT -5
On the digital board you will find CPU ic225. Off of pin 120 you will find R2225. Can you test for DC voltage on both sides of that resistor while attempting to power up?
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Post by jeremy on Apr 28, 2015 17:43:06 GMT -5
Those parts (would) be located on the top from what I can see on the HDMI/Digital board. However, R2224 and R2225 are not there, the pads to solder them on are there, but they aren't, so I don't know how I would check for voltage on both sides if not there |
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Post by mastertech on Apr 28, 2015 17:56:55 GMT -5
Ok, then that must be one of the differences between the 373 and 377. I am still working on getting the correct manual so we may have to wait until then.
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Post by jeremy on Apr 28, 2015 18:13:39 GMT -5
That's fine MT, I'm just glad to get some help with this  It's in too good of condition to give up on. But yeah you are correct, the HDMI board is fairly different between the 2 units. That and the amplifier in the 377 is discrete while the 373 uses the STKs. |
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Post by mastertech on Apr 29, 2015 19:18:38 GMT -5
On the digital board, look for connector CB222. test for DC voltage on pins 9,10,11 and 12. Test both plugged in and while bringing out of protect.
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Post by jeremy on Apr 30, 2015 10:41:46 GMT -5
ok while its plugged in, but not on (or in protect) there is no voltage on any of those pins. When its out of protect, Pin 9 reads -0.9vdc, Pin 10 reads 0vdc, Pin 11 reads +1.6vdc, Pin 12 reads +3.2vdc
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Post by mastertech on Apr 30, 2015 12:32:12 GMT -5
Go to the main board and locate Q68 and remove it. Then retest voltage at CB222 and see if pin 11 voltage increases to 3.3v
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Post by jeremy on May 1, 2015 9:40:05 GMT -5
Removed Q68 from the mainboard, tested voltage on pin 11 of CB222, it now reads +3.2vdc, up from +1.6vdc
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Post by mastertech on May 1, 2015 18:22:57 GMT -5
Ok, you must have some DC on one of those outputs. I am assuming you have diode tested the output transistors already. I don't know how easy it would be to probe the output lines while it is powered up because it would have to be before the relays and while coming out of protect.
If it was me and I could get to the output transistors and emitter resistors I would try doing a resistance measurement between the center tap of the resistor and the collector of both outputs. Test each channel and see if you find one that is way off from the majority. This should show any line voltage leaking to the output line.
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lol
It's in too good of condition to give up on. But yeah you are correct, the HDMI board is fairly different between the 2 units. That and the amplifier in the 377 is discrete while the 373 uses the STKs.
