saturn audio

[phreak97]

i got a bunch of saturns of a friend, the one im looking in now has no audio output. i traced the audio lines back to the phillips chip which is right behind the caps etc by the av out. i used a multimeter probe connected to the audio input to an amp.. probably not smart but i dont care, then i poked it at every pin on the thing. one of them returned very fuzzy audio, but audio none the less. im thinking this might be an input to the chip, since no sound comes out and goes to the av port.

the chip is labled

TDA 1386T
C54315
HfH9531 1 Y

if anyone can give me info on the thing it'd be much appreciated. a pinout would definately be nice..

i tried google, but i obviously dont know enough about the chip to get any decent results.

also a pinout of the audio processor chip would be nice, but ill understand if that doesnt exist.. it's got sega on it if its the right chip. google says the audio processor is made by yamaha, but if it is, it doesnt have yamaha on it, and this sega one is connected to the motorolla chip which supposedly controls the audio chip, so i guess its the sega one.

[davidleeroth]

www.datasheetarchive.com is the bomb.

[phreak97]

which numbers on the chip do i search for?  

[phreak97]

ok, i got the data sheet, and all the pins seem to be doing what they should as far as i could tell with a multimeter (obviously i couldnt test them all with a multimeter) except im not getting audio output. im getting a constant 2.something volts from each audio output, and thats all. the data input is there, and it's getting power, so wtf.. i even replaced the chip, but no change.

apparently theres something else interfaced with it according to the data sheet, but i dont know what..

help?

[Aidan]

A DC offset on the DAC outputs doesn't necessarily mean anything.

If you want to probe with an amplifier, then add a small capacitor in-line (like a 1uF) to block DC.

Did you check that both the analog and digital power/reference/grounds were at the correct voltages? That'd be pins 22 (reference voltage ~0.5v), 1 and 2 (analog supply/ground), 9 and 10 (digital supply/ground), 23 and 24 (opamp supply/ground).

You should also be seeing the correct clocks on pin 4 (data clock), pin 12 (system clock, 256 times the sample rate I think).

The chip you're probing is the DAC, which converts the digital data into the analog realm. If this is dead, then no audio would be present. Typically the DAC is then connected to an opamp or buffer before going to the outside world.

[phreak97]

ok, ill check the voltages and frequencies tomorrow if i have time.
it is not dead, i swapped in another one

i guess this is an untypical DAC then.. cos the outputs go through a cap and a resistor and not much more..

[phreak97]

im getting back onto this one.. it turns out the dac has a built in opamp for each channel, so that explains that.. what it doesnt explain though is why i can hear the music if i put a headphone from ground to data.. the music is rooted over, anything below a certain volume or outside whatever frequency range doesnt come out, and theres masses of fuzzy shit.. is that what's meant to be going into the dac? that doesnt sound like digital to me.. or maybe that's what happens when you make audio into square waves..

heres the data sheet: http://www.semiconductors.philips.com/acro.../TDA1386T_3.pdf

any ideas? i could even record what comes out of the data line and post it here as an mp3 if itll help

[Aidan]

That would be expected. You're evesdropping on the serial bus to the DAC, and your brain is intelligent enough to be able to recognise the patterns you're hearing as music. Effectively what you're doing is turning the 16bit signal into a 1bit signal, where each each of the 16bits has the same loudness. The 'hash' you hear is the low order bits, which have been given the same loudness as the high order bits.

Check both analog and digital power - if possible check the I2S clock signal and the sysclock for the DAC. If all those are good, then it may well be that the DAC has died.

[phreak97]

the dac is fine, i already replaced it as my first attempt

[Lost Monkey]

Have you tested a "working" Saturn in the same manner -just for control purposes?

[Aidan]

the dac is fine, i already replaced it as my first attempt

And the clock signals? If the clocks are not running or are not operating correctly, then you'll get not a lot from the DAC.

[phreak97]

when i tested it after i got it, im pretty sure i got the right frequencies..