Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Audio Equipment
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 08-06-2020, 11:40 AM   #1
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Yamahaha RX-V679 DC PRT High

Hey all,

I have a Yamaha RX-V679 that is entering protection mode after a few seconds of turning on. Shows "DC PRT 77H" error when I disable the auto protection.

All speaker terminals read ~0.4 volts across, except for the surrounds, which read 0 volts for right and ~0.9 volts on the left, which increases until the receiver kicks off. I'm thinking this is my problem child.

I took it apart and started testing the main output transistors, and didn't see anything blown open (I did this without desoldering, however I compared to nextdoor channel and all were very similar). The attached picture shows the transistors. Attached picture shows them.

Question is, what is my next step for testing?

Thank you for your help!

Service manual is located here, too big to attach

https://drive.google.com/file/d/1VtI...ew?usp=sharing
Attached Images
File Type: jpg 0805201422.jpg (593.3 KB, 13 views)
peterwheat is offline   Reply With Quote
Old 08-06-2020, 12:20 PM   #2
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

most likely the differential transistors . is there no dc offset adjusters ?
petehall347 is offline   Reply With Quote
Old 08-06-2020, 12:47 PM   #3
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Which ones are those?

Not that I am aware of, but frankly I'm not that knowledgeable on receiver electronics.
peterwheat is offline   Reply With Quote
Old 08-06-2020, 02:35 PM   #4
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

have you got a schematic ?
petehall347 is offline   Reply With Quote
Old 08-06-2020, 02:35 PM   #5
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Update:

I put things back together so I could reverify some voltages. I checked all the active speaker terminals for voltage again, and everything that's active is reading about 400 mV, with close to 0 on the non active channels. I had a speaker hooked up to one of them, and it sounded very distorted unless it was at a whisper like loudness.
peterwheat is offline   Reply With Quote
Old 08-06-2020, 02:36 PM   #6
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Quote:
Originally Posted by petehall347 View Post
have you got a schematic ?
Schematic should be in the service manual above, I can attach the main board pdf possibly?
peterwheat is offline   Reply With Quote
Old 08-06-2020, 02:38 PM   #7
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

need to check the power supply first . if thats wrong it will never work properly
petehall347 is offline   Reply With Quote
Old 08-06-2020, 02:39 PM   #8
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Quote:
Originally Posted by petehall347 View Post
need to check the power supply first . if thats wrong it will never work properly
Should I just be checking voltages coming out of the power supply then?
peterwheat is offline   Reply With Quote
Old 08-06-2020, 02:47 PM   #9
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

yes check those first .
petehall347 is offline   Reply With Quote
Old 08-06-2020, 03:29 PM   #10
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Quote:
Originally Posted by petehall347 View Post
yes check those first .
Checked these voltages, all correct. (within 5% or so)
Attached Images
File Type: png ps volt test 1.png (164.9 KB, 7 views)
peterwheat is offline   Reply With Quote
Old 08-06-2020, 04:17 PM   #11
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

look for the -12.4v rail .
petehall347 is offline   Reply With Quote
Old 08-06-2020, 04:31 PM   #12
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

On the main board, correct?
peterwheat is offline   Reply With Quote
Old 08-06-2020, 05:03 PM   #13
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

yes .if you look at the input to the amps on the schematic its there .
petehall347 is offline   Reply With Quote
Old 08-06-2020, 05:09 PM   #14
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

also measure at for example Q1002 base .should be 0v ..i ask this because offsets are high when active . might be stray voltage getting in here .
i have a feeling the fault might be the input switching chips .
lets see those voltages first though before i get carried away too much .
petehall347 is offline   Reply With Quote
Old 08-06-2020, 05:47 PM   #15
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Reads at -12.2V
peterwheat is offline   Reply With Quote
Old 08-06-2020, 05:57 PM   #16
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

Quote:
Originally Posted by petehall347 View Post
also measure at for example Q1002 base .should be 0v ..i ask this because offsets are high when active . might be stray voltage getting in here .
i have a feeling the fault might be the input switching chips .
lets see those voltages first though before i get carried away too much .
Q1002 is in a Y shape, from the bottom of main board

-0.45V 0V

56.58V
peterwheat is offline   Reply With Quote
Old 08-07-2020, 01:53 AM   #17
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

what does it measure when that channel inactive ? like not selected .
petehall347 is offline   Reply With Quote
Old 08-07-2020, 02:19 AM   #18
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 38,511
Default Re: Yamahaha RX-V679 DC PRT High

Quote:
Originally Posted by peterwheat View Post
Hey all,

I have a Yamaha RX-V679 that is entering protection mode after a few seconds of turning on. Shows "DC PRT 77H" error when I disable the auto protection.

All speaker terminals read ~0.4 volts across, except for the surrounds, which read 0 volts for right and ~0.9 volts on the left, which increases until the receiver kicks off. I'm thinking this is my problem child.

I took it apart and started testing the main output transistors, and didn't see anything blown open (I did this without desoldering, however I compared to nextdoor channel and all were very similar). The attached picture shows the transistors. Attached picture shows them.

Question is, what is my next step for testing?

Thank you for your help!

Service manual is located here, too big to attach

https://drive.google.com/file/d/1VtI...ew?usp=sharing
So the Surround Left is the only one that has output offset that goes too high after a while then the receiver goes into output high DC shut down?

Is it Surround Left? Or is it Surround Back Left? I ask because you were asked to check Q1002 which is for Surround Back Left, not Surround Left. Please Clarify as to which Left channel is bad.

Below is for Surround Left checking:
Once it goes into shutdown,what DCV do you get on jumper J245 (close to Surround Left output inductor L6, see service manual PDF page 118)?
Is it Positive or Negative Voltage reading with ref to GND?
Attached Images
File Type: jpg Surround Left output test point.jpg (660.5 KB, 5 views)
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809

Last edited by budm; 08-07-2020 at 03:13 AM..
budm is offline   Reply With Quote
Old 08-07-2020, 08:17 AM   #19
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 2,344
Default Re: Yamahaha RX-V679 DC PRT High

i only used Q1002 as an example .. its fairly straightforward looking at the schematic .
from what i read offsets are only high when channel is active . and not just one channel . 400mv offset .
i haven't studied whether it cuts the speaker off or mutes the input when not selected .

Last edited by petehall347; 08-07-2020 at 08:22 AM..
petehall347 is offline   Reply With Quote
Old 08-07-2020, 10:00 AM   #20
peterwheat
New Member
 
Join Date: Aug 2020
City & State: Huntsville
My Country: United States
I'm a: Knowledge Seeker
Posts: 18
Default Re: Yamahaha RX-V679 DC PRT High

SR: 0.353
SL: 0.302
C: 0.300
FR: 0.358
FL: 0.305
SBR: -0.009
SBL: 0.814

Those measurements are with all channels selected.

waiting on it to kick off so I can measure the jumper now.
Attached Images
File Type: png ps volt test 2.png (15.3 KB, 2 views)
peterwheat is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2020
Powered by vBulletin ®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 11:00 AM.
Did you find this forum helpful?