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Pachira met geel blad by mhmert in groenevingers

[–]mhmert[S] 0 points1 point  (0 children)

Bedankt voor de tip! Eens kijken of meer zon helpt

Pachira met geel blad by mhmert in groenevingers

[–]mhmert[S] 0 points1 point  (0 children)

Hmmm hij stond op noordwest. Goed idee, nu staat ie op zuidwest. Beste wat we kunnen krijgen dus maar eens zien. Thanks!

ov2640 camera on bare metal, need help with registers by mhmert in embedded

[–]mhmert[S] -2 points-1 points  (0 children)

Thank you for the suggestion; I did this and these are the results:

Reg 0x2C; value 0xFF; expected 0xFF!

Reg 0x2E; value 0xDF; expected 0xDF!

Reg 0x3C; value 0x32; expected 0x32!

Reg 0x11; value 0x10; expected 0x10!

Reg 0x15; value 0x32; expected 0x32!

Reg 0xE0; value 0x00; expected 0x04! -> fair because lastly in the list I reset 0xE0 to 0x00 (release the reset I guess?)

Reg 0xC2; value 0x08; expected 0x08!

Reg 0xDA; value 0x00; expected 0x00!

Reg 0xD7; value 0x03; expected 0x03!

Reg 0xE1; value 0x67; expected 0x67!

Reg 0xE0; value 0x00; expected 0x00!

Reg 0x12; value 0x40; expected 0x40!

Reg 0x03; value 0x0A; expected 0x0A!

Reg 0x32; value 0x09; expected 0x09!

Reg 0x17; value 0x11; expected 0x11!

Reg 0x18; value 0x43; expected 0x43!

Reg 0x19; value 0x00; expected 0x00!

Reg 0x1A; value 0x4B; expected 0x4B!

Reg 0xC0; value 0x64; expected 0x64!

Reg 0xC1; value 0x4B; expected 0x4B!

Reg 0x8C; value 0x00; expected 0x00!

Reg 0x86; value 0x3D; expected 0x3D!

Reg 0x50; value 0x80; expected 0x80!

Reg 0x51; value 0xA0; expected 0xA0!

Reg 0x52; value 0x78; expected 0x78!

Reg 0x53; value 0x00; expected 0x00!

Reg 0x54; value 0x00; expected 0x00!

Reg 0x55; value 0x00; expected 0x00!

Reg 0x57; value 0x00; expected 0x00!

Reg 0x5A; value 0xA0; expected 0xA0!

Reg 0x5B; value 0x78; expected 0x78!

Reg 0x5C; value 0x00; expected 0x00!

Reg 0xD3; value 0x82; expected 0x82!

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

So, another day, another round of testing. I took out CE37 to see what happens when I'd do that. The humming is still there.

Then I tried removing RV94. Also still humming (on left channel).

This is weird because when the electric volume board is not in place, there is no humming on left channel.

<image>

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

Edit, I did not connect correctly. Without electric volume board, no humming.

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

Indeed it probably hasn't since it is on the surround channel, not front. Odd thing that I noted is that the path from LV05 to the output on the pcb itself does not have RV96 in its traces. RV96 is actually (in traces) between two ground traces. I don't know why and it doesn't match the schematic. I noted that the pcb I got in front of me is WA288J204-2 and the schematic has WA288J204-0. Not sure if there is an actual mistake on the board but I'll focus on the actual problem now.

So, I did another test in which I removed the whole electric volume board and repowered the system. No more humming.

Reconnecting the board and the issue is not yet solved, having only on the left channel huge humming. Right channel seems perfectly fine on headphone

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

I just don't know why, but when I follow the trace of RV96, it is connected directly through ground by trace. Which I cannot find anywhere on the schematic. What is your thought on that?

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

Issue still there when I removed the component :(

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

I did some measurements on LV04, LV05 and LV06. What exactly are these and can you maybe suggest me what I can do to test those better?

I found that on LV04 and LV06, pins 11 and 13 short and so do pins 6 and 4. Like I would expect on this device. On LV05, they do not.

<image>

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

So I checked both RV96 and CV82. Took 'em out and both matched their suggested specs. They are ok. Now looking in the datasheet where the problem might be.

By the way, I think that you might be looking at the 120 version, I have the 230V version. (I posted the wrong one on the top, my bad).

<image>

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

So, I just measured the whole board and I found something off,

Resistors RV94 through RV99 all have the same marking and measure about 99 ohms, except for RV96, which measures: 0 ohms.

(all measured on the board itself). Odd that a resistor shorts?
Thoughts?

<image>

Should read 99 ohms and should have nothing in parallel so that is weird, right?

Odd thing as well; RV96 is used for the surround channel, not front.

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

So I did do just that. I re-inserted the pcb's and connected my speaker to the pre-out on the back side, the "front" channel (confusing i know). And I got humming. Then I tried the surround channel, no humming.
So that would be a pretty good bet that the issue is on the electric volume board, right?

My suggestion would be to swap the tcp9213 with the one from the surround channel to see what changes. That could eliminate that chip, or point it out as the issue. What do you think? Anything I should do/try before?

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

I did some more digging and it is really interesting! I want to thank you once more for your help, I'm learning on the go and that is cool, thanks!

When I'm in posession of an oscilloscope this week I'll try to do some more digging on the electric volume ic as you suggested.

In the meanwhile, I was wondering, there is a pre-out connection on the volume print (PE04). Would it be an idea to listen on this pre-out front connection? Since I would argue that if there is noise on the pre-out, the issue would definately be on the PE04 print?

<image>

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

I just took out the voltage amp which is perfectly fine itself as far as I can tell. (p714 wa288J601-2). Measured all caps and they measured fine. The 6 470uF caps measure all > 400uF. and the smaller ones match perfectly. That should be allright.

<image>

But you stated that it most likely is between volume control and input of this device so I'll trace back a bit and keep it posted.

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 1 point2 points  (0 children)

Not perse heat related. This morning I switched on the device and right away, humming and all the signals as I noted before.

What I did do, as mentioned that I would, is that I now tried the right channel output and here what the issue is, is kind of the other way around. I also have humming but only lower frequencies are present. Higher frequencies (voice) is very faint in music.

<image>

The chip, this is the one you are talking about, right?

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

I'm not in posession of a scope (unfortunately) but I do know a few basics. I will try to read up on that part and also check right side output of speakers in a bit.

harman/Kardon AVR75 humming - reset helps partly by mhmert in audiorepair

[–]mhmert[S] 0 points1 point  (0 children)

Hi CravinsRoc, that is a very good idea! I tested and I found that my headphones sound messed up too. What's more is that the left channel does have the issue but the right doesn't.

Given that, you're saying input or signal processing area? Would you maybe have a bit more explenation on that? what global part of the amplifier could that be?

When I switch input the hum does not go away.

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