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Old 11-05-2019, 01:24 AM   #1
Kosti
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Default Yamaha RX-V3900 Powers On then Off (Protect)

Hi All,

The receiver is shutting down on abnormal voltage protection, with the message "PS3 PRT 181" (norm 114-180). I assume the issue points to the POWER (3) so I got into the diagnostic mode and measure some of the voltages at the points to the main transformer and these seems close to there values as found on the schematics

CB15
AC 9.9 (GY): Pin1 10.47V ac
AC 9.9 (GY): Pin2
AC 30 (WH): Pin5 15.76V ac
AC 30 (RE): Pin6

If I measure across Pin4&Pin6 I get the 30V ac. I suspect the schematics is wrong as I get +- 20V across the rectifier, hence the measurement point should've been across those pins not 5&6 but 4&6 to get 30V AC

I also measure the voltages across POWER 1 connector to mains transformer and get

CB11
AC 6.8(YE): 6.53 V ac
AC 15.8(PU): 16.37 V ac
AC 9.1(OR): 9.64 V av
AC 9.2(BL): 9.09 V ac

I performed some other measurements and got close to the values as shown in the schematics however in most cases these voltage values would seems to be within tolerance, but have concerns due to the way this AMP performs its protection checks via a voltage summation circuit to monitored the voltages and triggers it to go into protection shut down

Now I've I got into the diagnostic mode and also replaced the common fault: C405 (it's C4 in this one) just as a precaution.

I've attached a few pages and full schematics found below

RX-V3900

I am hoping people can help me find the cause to fix this AMP
Thanks

PEACE
Kosti
Attached Files
File Type: pdf Schematics.pdf (52.3 KB, 5 views)
File Type: pdf schm.pdf (942.5 KB, 6 views)
File Type: pdf schm2.pdf (805.2 KB, 3 views)
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Old 11-05-2019, 10:28 AM   #2
R_J
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

PS3: Detects +5VA, -5VA, +9VA. Check those voltages to make sure they are ok
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Old 11-05-2019, 02:38 PM   #3
redwire
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

You can see PS3 the MCU monitoring voltage divider at R75,R76,R77 for "PRVS". It adds the three rails together. The displayed number is raw 8-bit A/D count 0-255.
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Old 11-07-2019, 11:28 PM   #4
Kosti
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

Quote:
Originally Posted by R_J View Post
PS3: Detects +5VA, -5VA, +9VA. Check those voltages to make sure they are ok
OK great thank you, I will try and check this on this weekend, Its a big amp and I have to keep moving if off our dinner table to work on it

Quote:
Originally Posted by redwire View Post
You can see PS3 the MCU monitoring voltage divider at R75,R76,R77 for "PRVS". It adds the three rails together. The displayed number is raw 8-bit A/D count 0-255.
Thank you,

EDIT, makes sense now that I looked at the schematic
R75 - 47K ,R76 - 27K ,R77 - 27K
I will measure these when I get the opened up and report back.

Just to add there will be some delay as I was measuring the caps on the PS1 around C4 area and found the 3300uf to be out so have ordered some of these to replace so hopefully they arrive next week

PEACE
Kosti

Last edited by Kosti; 11-08-2019 at 12:22 AM.. Reason: updated details
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Old 11-17-2019, 07:04 PM   #5
Kosti
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

Hello All

I've finally had a chance to get back to this today, so I have looked to confirm the voltages of these regulators based on what PS3: Detects +5VA, -5VA, +9VA at CB23.

Checking those voltages reads +4.94VA -4.94VA & +8.99VA so they are ok right?

So do I need to measure R75 - 47K ,R76 - 27K ,R77 - 27K values if the voltage readings are close to values? I will try and do this but given they are on the flip side of the board, its dismantling the whole amp which I wanted to avoid.

FYI - I also replaced the 2 x 3300uf caps on PS1 as well since these were also out in value thinking the ripple may be contributing, but still no luck in keeping this to stay on.

So if diagnose code shows PS3 PRT 181 and the voltages check out ok where would I start to zoom in on the issue if PS3 is reporting to be ok?

Hoping for some further clues chaps, as always, thanks for the guidance

PEACE
Kosti
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Old 11-30-2019, 07:33 AM   #6
Kosti
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

Hi All

Anyone have any further idea of why this amps shuts down? Basics checks seems to come up ok and the receiver is shutting down on abnormal voltage protection, with the message "PS3 PRT 181" (norm 114-180).

I've checked the voltages of PS3: Detects +5VA, -5VA, +9VA. to make sure they are ok and they are measuring +4.94VA -4.94VA & +8.99VA.

Really need some guidance chaps

PEACE
Kosti
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Old 11-30-2019, 04:54 PM   #7
CapLeaker
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

Try warming PS3 with an hair dryer so the PSU is warm, not hot so you can’t touch it anymore. Turn the amp on and see if the problem presists.
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Old 11-30-2019, 06:23 PM   #8
R_J
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Default Re: Yamaha RX-V3900 Powers On then Off (Protect)

Check the voltage on CB18 pin 3 (PRVS) [page 154 of manual] it should be 2.8~3.2v
If you look at page 114, locate IC402, to the left is R4039, check the voltage on each side, it should have 1.1v on the test point.
This is the line that is triggering the PS3 error, so maybe there is a poor connection somewhere between the power supply and the micro.
Attached Images
File Type: jpg PVRS_R4039.JPG (143.4 KB, 3 views)

Last edited by R_J; 11-30-2019 at 06:42 PM..
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