Help with Onkyo TX-NR646

[mmartell]

I thought this was dead as it wasn't showing any outward signs of life but after cracking the lid I measure the Standby voltage of 12v.

From what I can tell all the sub voltages to drive the micom, memory and mcu etc are created on the hdmi board from the standby voltage as soon as mains are connected. It's hard for me to follow the schematics but logically there seems to be a common failure preventing ALL sub voltages from coming up.

Attached is a copy of the service manual. As always, any help is appreciated.

[dobrykamil]

Re: Help with Onkyo TX-NR646

Page 42, Power supply section.
When you push on/off button, do you get voltage drop at pin MPOWERD? Also, check impedance of the main relay.Should be around 300-330Ohm. Take a look at the page 20 too. I own this model, so I'm more than happy to answer any questions.

[mmartell]

Re: Help with Onkyo TX-NR646

There is no standby led and no other voltages present at any pins off the hdmi board so I think the mcu is not running but will test and post back.

[mmartell]

Re: Help with Onkyo TX-NR646

As per the SM there should be 3v at MPOWERD. I have identical voltage there as I do at pin4 (standby voltage) of 11.44v. There is no change when pressing the power button.

[dobrykamil]

Re: Help with Onkyo TX-NR646

Page 52, what voltage to you get at the Base of Q7016 when pressing power button?Check Vout's of the power IC's near Q7009.

[tibimakai]

Re: Help with Onkyo TX-NR646

Make sure, that the ribbon cable that is coming from the front board, is making good contact at the HDMI board.
Once I had one, with a ribbon cable, that was cut to narrow and it was inserted into the connector, to one side and the pins did not make contact. They were offset.
You don't hear any click at all?
I have two of these.

[mmartell]

Re: Help with Onkyo TX-NR646

Make sure, that the ribbon cable that is coming from the front board, is making good contact at the HDMI board.
Once I had one, with a ribbon cable, that was cut to narrow and it was inserted into the connector, to one side and the pins did not make contact. They were offset.
You don't hear any click at all?
I have two of these.

I've checked that cable at the hdmi board and it looks good. The other side however... I have not yet removed the front panel to check it. It almost seems like the board is not connected at that end. Except I still would expect to see the 5v on that ribbon which I do not have so I think the problem may be deeper than this.

[mmartell]

Re: Help with Onkyo TX-NR646

Page 52, what voltage to you get at the Base of Q7016 when pressing power button?Check Vout's of the power IC's near Q7009.

That transistor turns on the relay for the main transformer ? Will check it out.

By the way I previously jumped MPROTECTD to ground and the main relay clicked, if that helps any.

[dobrykamil]

Re: Help with Onkyo TX-NR646

That transistor turns on the relay for the main transformer ?

Yes.

By the way I previously jumped MPROTECTD to ground and the main relay clicked, if that helps any.

Did the unit shown any signs of life at that point?

[mmartell]

Re: Help with Onkyo TX-NR646

I had the transformer unplugged because I was just checking if the relay would latch.

[mmartell]

Re: Help with Onkyo TX-NR646

Can't find Q7016 but the Micom Q7009 is only getting a steady 0.282 volts so something is dragging it down. Any suggestions on how to track that down ?

[R_J]

Re: Help with Onkyo TX-NR646

Do you have +5 volts into Pin 1 of Q7018, is Q7018 getting hot? Disconnect P701a cable going to the display, it is connected to the 3.3 volt line

[mmartell]

Re: Help with Onkyo TX-NR646

Can't find it ? Maybe it's on the underside will have to remove the board from the unit.

[mmartell]

Re: Help with Onkyo TX-NR646

Found those in question on the underside of the board. I made a resistance check and am measuring a dead short on the 3.3v line to Q7009. Will have to pull some filters and see if the Micom has shorted.

[mmartell]

Re: Help with Onkyo TX-NR646

The 3.3v reg Q7018 and diode D7006 were both getting hot when circuit was powered. Not only do they test fine out of circuit the short remains.

[mmartell]

Re: Help with Onkyo TX-NR646

Do you have +5 volts into Pin 1 of Q7018, is Q7018 getting hot? Disconnect P701a cable going to the display, it is connected to the 3.3 volt line

Yes I am getting 5.2v into pin 1 and it was getting hot. That was tested out of the unit with an external 12v supply and nothing else connected to the board.

[R_J]

Re: Help with Onkyo TX-NR646

Coud you tell if anything else was getting hot, Like any of the ic's or possibly one of those chip caps on the 3.3 volt line, If you have a bench supply you could put about 1 volt or less with limited current to the 3.3 volt line and see what gets warm.
I sometimes just use a 1.5 volt battery and touch the line momentarily while a finger is on a suspected part to see if it gets hot.

[mmartell]

Re: Help with Onkyo TX-NR646

I did not see anything else getting hot but I must be missing it. I guess the regulator would heat up if too much current was being drawn through it.

Will do as you suggest and inject voltage on the other side of the reg and report back in the morning.

[mmartell]

Re: Help with Onkyo TX-NR646

Found the short ! Injected voltage on the other side of the removed regulator and found Q7013 getting hot. After removal the short was gone.

I have none of these ic's on hand don't know if I've come across one before. Can get from Digikey but will go over my junk pile first.

[R_J]

Re: Help with Onkyo TX-NR646

Good find, the unit should work without the ic so you can check the rest of it, looks like its just for cec