TDA1541 info

[Andypairo]

another question on the TDA1541A..

Hi all,
I'm playing with a TDA1541A and have noticed a odd behaviour from one chip: as soon as I apply power it sounds distorted but when I start checking pin voltages with my oscilloscope as soon as I touch pin 17 sound becomes OK and stays like that.

It looks like the DEM oscillator has troubles starting the oscillation.... btw I use a 470pF cap.

This happens with a chip dated 1994, while another chip dated 1997 works fine....

Any clue about that?

Cheers

Andrea

 

[tubee]

Cap to perfect, allmost no leakage? Maybe adding a bleeding resistor to gnd of 1 or 2 megs.

 

[QSerraTico_Tico]

Some chips have built in cap.
Check with test CD and low level sine wave.
If the oscillator is not working gross crossover distortion

 

[Andypairo]

Cap to perfect, allmost no leakage? Maybe adding a bleeding resistor to gnd of 1 or 2 megs.

Err... do you mean that the DEM oscillator needs to leak some current to properly start?

Some chips have built in cap.
Check with test CD and low level sine wave.
If the oscillator is not working gross crossover distortion

The TDA1541 has the cap built-in .
The 1541A doesn't.
No need to check with sine, music is very distorted until I touch the pin 17 with my oscilloscope probe.

I am just asking if anyone experienced this problem and if found a way to cure it (bigger/ different cap, etc...)

Cheers

Andrea

 

[QSerraTico_Tico]

Err... do you mean that the DEM oscillator needs to leak some current to properly start?



The TDA1541 has the cap built-in .
The 1541A doesn't.
No need to check with sine, music is very distorted until I touch the pin 17 with my oscilloscope probe.

I am just asking if anyone experienced this problem and if found a way to cure it (bigger/ different cap, etc...)

Cheers

Andrea

Bad chip?
Never experienced that what you described.

 

[Andypairo]

Addendum to the oddities

Hi,
while testing some chips I plugged in a TDA1541.

This chip is supposed to have a internal DEM oscillator cap (datasheet shows pin 16 and 17 unconnected).

To my surprise leaving them disconnected distortion was rocket high. Putting the cap in made it lower to reasonable levels.
Using DEM reclock lowered it further. Go figure!

The chip used is late 1541 production (1987, and also has a Y printed, that, if I recall correctly, was mentioned to be meaning "development sample")....maybe a early 1541A?

Anyone had similar experience?

Cheers

Andrea

 

[tubee]

I am a strong believer the TDA1541 nor the 1541-A cannot function without the dem cap or an external provided dem signal.

 

[Andypairo]

hi,
so why release a chip that doesn't work as stated in the datasheet?


BTW did you happen to look at the DEM reclock signals with your scope? I use HtP's original schematic and I see a rather large negative peak (will take a photo soon).

Cheers
Andrea

 

[tubee]

Philips did some curious things with the 1541.

I have looked at the dem signal, but it is for a while now, can't remember exactly.

Btw sit right here listening to Rush, Signals, with a plain 1541 (no A) in CD304mk2 with the dem clock, not HtP's but Ec's

 

[philpoole]

so why release a chip that doesn't work as stated in the datasheet?

I used to work for a large european semiconductor manufacturer (not Philips) and I can say, as useful as they are, datasheets can be wrong at times.

 

[Andypairo]

Hi,

datasheets can be wrong at times

This is certainly possible, but I doubt nobody verified it.

Surely there are players around with TDA1541 and without the Cosc cap

Example:

An externally hosted image should be here but it was not working when we last tested it.

Does anybody have a direct experience?

Cheers

Andrea

edit: maybe the Cosc is under the green ceramic...wrong example in that case

 

[tubee]

maybe the Cosc is under the green ceramic...wrong example in that case

Maybe post a picture of other side of pcb.

 

[Andypairo]

Hi,
the picture was taken on the net, so I can't flip the PCB and see underneath.

The question about TDA1541 (without A) remains the same.
Surely someone around here has a player with such a chip....

Cheers

Andrea

 

[Katapum]

http://www.diyaudio.com/forums/showthread.php?postid=1253207#post1253207

 

[Andypairo]

Katapum,
the photo in the post you link shows that the PCB had a provision for the Cosc capacitor but it seems that it wasn't mounted. Or did you remove it?

Can you confirm?

Cheers

Andrea

 

[Katapum]

Katapum,
the photo in the post you link shows that the PCB had a provision for the Cosc capacitor but it seems that it wasn't mounted. Or did you remove it?

Can you confirm?

Cheers

Andrea

I see a SMD cap (CD160 manual says 680p and a 1541P )

 

[QSerraTico_Tico]

Re: Tda1541a info

hi,

I had some detail TDA1541a info from the philips factory when I design the parallel TDA1541a D/A board.
its a PDF format approx 60~70 pages.
Anyone who had interest pls email to me.
I zip already & will email to him.
hope this can help U.

this is my email.

thomas@diyaudiocraft.com.

thanks

thomas

Anyone has this document???

 

[tubee]

At that time i asked him for it and received a standard data sheet, not in 70 pages.

 

[QSerraTico_Tico]

Hoax?

At that time i asked him for it and received a standard data sheet, not in 70 pages.

Maybe a HOAX?

 

[tubee]

PM him.