Philips CD880. Where do I start?

[Morzh]

Binkman

I agree with most of what you said.
I think a good quality low ESR cap cannot affect sound quality simply because its time constant is too low.
High ESR cap potentially could, as its time constant could actually get into audio frequency band.
A cap whose ESR has drifted up significantly is simply defective and should not be used.

Caps with low ESR are needed at outputs of switchers as this affects ripple voltage.
Bulk caps could very well be genetal purpose caps, as they are always (in well-designed circuits) parallelled by cetamic caps that can quench fast transients the electrolytics cannot.

In power amp section however (well, I don't have it in here) power filtering caps are important as they keep the VCC constant during peak (and regular) loads, without good cap there you will have sagged wavefor during fast transient. They also compensate for wires' inductance so additional bulk ones at the board power entry are very desirable.

At any rate, do not put Lelon caps anywhere. They are just bad. Even though sold by reputable sellers

This said, where there is subjective perseption there is always some snake oil, like normalized impedance speaker cables and such. Blind tests historicall embarassed many self-proclaimed gurus.
I think Hans Christian Andersen in his "Kings new clothes" described it best.

 

[redk9258]

Toshiba power supply schematic..

 

[Morzh]

Where the voltages are shown, in two places the WV of the caps is 20 to 25% over the operating voltage.
Though one of them, 2200uF according to you is ok.
Then again, they are 85C.
What I also don't know is, what caps those were, GP or LESR/HRC.
Water under the bridge, if you put in higher voltage higher temp LESR caps, they might outlive the TV

My bad news, the power supply did not start after being put back. Putting it back was a challenge.
Now comes troubleshooting. I didn't do nothing! Why!!!

 

[redk9258]

What I also don't know is, what caps those were, GP or LESR/HRC.
Water under the bridge, if you put in higher voltage higher temp LESR caps, they might outlive the TV

I think they were just general purpose caps all 85 degree Celsius except 2 were 105 degree. I mostly used Nichicon PW series except for 1 that wasn't available in that series. I used Nichicon VZ there. I used all 105 degree caps.

 

[redk9258]

My bad news, the power supply did not start after being put back. Putting it back was a challenge.
Now comes troubleshooting. I didn't do nothing! Why!!!

I hope you get it going!

 

[Morzh]

For higher voltages I like Panasonic EB, to compare

EB 22uF 450V Ir=560mA @120Hz
PW 22uF 450V Ir=115mA @120Hz

But still PW is low impedance and 105C.
A GP caps simply should not be used in switchers.
Lots of ripple, lots of noise.

 

[Morzh]

Here's one thing I found.
I am sure this was the result of that warp I straightened out, only it might have some residual contatct and after it was handled it lost all of it.
I will touch up the rest of heatsink-mount parts.
Hope this is it, if I am lucky.

 

[Morzh]

In addition, I decided to ispect the connectors.
I found lots of cold solder spots around thick pin ones, from the transformer and inter-board.
An example: (see the top pin).


So every connector, every TO-220 part got touched up.
Not sure what resulted in this. Shipping? How many times? Vibration? From where?
Let's say I am not impressed with Philips soldering.

 

[Morzh]

Today was the soldering day.

I first soldered every TO-220 part on the heatsink.
Then I decided to inspect the board and while looking at large connectors (transformer to board, the outputs to the motherboard) and found a few pins looking like this: (the top pin).




So all the connectors, including the smaller ones, got some serious touch up.
Then upon inspection I noticed some small parts pins developed indentations around them some look like cracks started to develop.
I touched them up, some sputtered or cracled at me, I guess entrapped flux. Large hole were revealed, meaning the holes are much larger than the pins, and I am not sure the barrel is metallized, but if it is, the solder did not rise yp and remained a thin layer around the pin, which made it easy to crack. Well soldered barrel does not allow that to happen.

Then since the same large connector is on the motherboard, I also removed it (AGAIN!!!) And sure enough, saw the cracked solder, so I touched all pins up, and also did touch up the sole TO-220 part on it.

Then installed the power unit, and without connecting loads measured voltages.
All voltages are fine except one, +10V. I briefly investigated: the voltages are made with 8V 7808 LDO with the common connected to GND via 2.2V zener, which makes it output 10V. But the zener needs a bias, and it is provided with a 1.2k resistor. Of which one pin seems disconnected. So the Zener is not biased and the 8V LDO outputs 8V like a good boy he is.
I decided to wait until tomorrow: removal and installation of the power supply is an onerous thing.

 

[Morzh]

So....the Zener was connected after all.
It is simply shorted. So instead of 2.4V it drops 0V. Hence 8V instead of 10V.

I unsoldered one pin to make sure it is the Zener and not something else.

Now off to get the Zener.

 

[Morzh]

So. The Zeners came yesterday (50 pcs for $1.50 plus $3.25 shipping). Today I installed it, check the 10.5V and it was exactly on the spot.
The CD worked with it being 8V, I guess it might be the VCC for some op amps and usually there is some margin plus common mode rejection for the power supply is anywhere from 90 to 120dB (didn't bother to check the datasheet...it works).
Anywho. I connected everything, and upon the button press the CD tray happily, easily, without any help rolled out.
I took it to the stereo setup, and it played just fine.
I need the remote to control the volume, the player came without it. I could buy a generic replacement for $13, or try to get the real one, which could, with shipping, easily get to a $100.
But so far I use the fixed output
What I thought was the volume control is indeed it, but for the phone output.
The potentiometer is bad. It is really scratchy, with some dead zones....and there is no good way to deliver the Deoxit inside, the diameter of the bushing being small. Right now I don't care as I don't use phones. I will explore where to but a new one....willy-nilly, not a priority.
So, to recap:
1. The table roll-out fixed (the ew PRB belt), Lube and all also done.
2. The dent in the back and the consequences are removed.
3. The bad connections are fixed across the device (Power, Main Board, Phones board).
4. The incorrect +10V voltage (8V) fixed by replacing the bad Zener.


When I buy the remote, this thing will be complete.