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Old 29th January 2015, 01:56 AM   #1
mk13139 is offline mk13139  Netherlands
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Join Date: Feb 2014
Default Denon DRA-335r problems

Hi,

I just received a Denon DRA-335r. It is playing perfectly fine, however there are some minor issues with it.
The first problem is that the display is flickering irregularly. Could this be a problem with the 5v line or is the display dying? I tried to find IC605 (7806), which is responsible for the 5v, but I can't seem to find it anywhere on the board.
According to the schematics it should be near by D604, D605, C644 and the bridge rectifier. However D604, D605 and C644 are not near the bridge rectifier, infact they are on the other side of the board. And D604 D605 C644 are not connected to IC605, but IC604 (7812) on my board! Strangely I do measure 5v on D604 but IC604 is running very hot, I can bearly even touch it.

This is the layout of my board: link
As you can see the bridge rectifier is bottom right, but in the left upper corner you can see a yellow cap and a black cap, C643 and C645, and not far from it IC604.


The second problem is the remote volume control, I can turn the volume up but I can't turn it down with the remote. This has probably to do with the motor driver, IC251?
Maybe this has something to do with the flickering display/5v line?


Any suggestions are welcome!
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Old 30th January 2015, 05:18 PM   #2
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Join Date: Nov 2004
Location: Germany
Display problem: Resoldering the pins responsible for the heating on the VFD may be all it takes there. Since VFDs tend to get warm, they also tend to develop bad solder joints.

Volume control: Have you checked whether the remote actually sends something on volume down? Can you possibly hear the motor operating? (Could be a tight motor, too. Does it do something with some manual help?) Otherwise it would have to be driver related - either it doesn't receive the volume down signal, or it's just a bad chip. A bad chip may still indicate mechanical issues.
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Old 21st February 2015, 12:34 PM   #3
mk13139 is offline mk13139  Netherlands
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Join Date: Feb 2014
I resoldered all the pins of the VFD, but no avail..
One thing to notice is that when I press and hold any button on the remote, the display stops flickering.
Since all IO have 5V pull up resistors connected to them, could this still indicate noise on the 5V line?

I have narrowed down the problem to the logic board (IU-2346), because I have replaced all the caps, diodes and the IC responsible for the 5V and VDD.
Could it be one of the transistors or caps on the logic board? I have no idea where to look, since I can't exactly relate the behaviour of the VFD...
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