Logitech Z506 with corrosion

[Traptor]

Hi Guys,
I have a Logitech Z506 with some problem.
The main problem was the front right and subwoofer gave a hard noise.
After the disassemble I found many corrosion on the mainboard as you can see on the pictures.
I removed the corrosions and the noise disappeared but the sound too.

I think some parts is damaged because of the corrosion.
I searched a lot on the internet but I cant find correct schematic for this pcb, so I dont know what is the correct values of the damaged parts.
But I found same good pictures of this board.

If you anybody can help me please don't hesitate.

So, I need values for R403, R404, R426

[alfatv]

Re: Logitech Z506 with corrosion

Yes, SMT resistors are more likely to fail from corrosion.
You have few options:
- Find picture of a good board
- Find out part number of that IC, then find datasheet and check reference circuit. But this will not work in case of opamps.
- If the same chip used in another circuit on the same board, check what components are there.
If you are really determined, you can reverse engineer it and draw a circuit.

[jons]

Re: Logitech Z506 with corrosion

Clean all that yellowish stuff also because it will corrode anything underneath. It is the same as brown you cleaned, only in second not third phase of transformation.

[Traptor]

Re: Logitech Z506 with corrosion

Thank you the suggestion, I got the information.
R403 = 15 kohm
R404 = 47 kohm
R426 = 47 kohm

[Traptor]

Re: Logitech Z506 with corrosion

You are right.
Have you any idea for cleaning method?

[Traptor]

Re: Logitech Z506 with corrosion

OK I found a simple method for cleaning: I heated the glue with a hot air station to 100 C and the glue softened and than I could removed that.

[nobbnobb1]

Re: Logitech Z506 with corrosion

Did your repair end up working out? That looks really nasty! I never knew that some heat would help remove the glue...I've always had to chip it away manually.

I'm also curious how it managed to get that bad in the first place. Do you live somewhere hot? Looks like the corrosion got bad enough that things started shorting out in a significant fashion.

[Traptor]

Re: Logitech Z506 with corrosion

Yes, I repaired the Z506.
The heat helped to remove the glue because the hard glue softened.
I live in Hungary in middle Europe so I dont think the weather is the reason of corrosion. Btw I saw lot of picture of Z506 with corrosion pcb.
My opinion is the used glue is not a good quality.

[jons]

Re: Logitech Z506 with corrosion

I'm also curious how it managed to get that bad in the first place. Do you live somewhere hot? Looks like the corrosion got bad enough that things started shorting out in a significant fashion.

It's mostly glue's chemical composition which reacts with natural moisture in air, nothing to do with heat. And that glue manufacturers used from early 80's, here some 1981 HK amplifier which I had recently but examples are countless.