I downloaded the service diagram for my Sony STR-KM 5500 home theatre amplifier but cannot find the Pre-amp section
Some smt but there’s alot of caveats around thermal joint stress as it’s more brittle. One real problem is mixing with lead solder (pre-tinned etc) results in a very brittle <100degC melting joint.
For me i would perhaps look at to for QFN but not for high output thermal ground pads.
Preamp is IC400, located on Main 2/3, page 27. DAC is IC1452, Digital AB 1/3, page 31. The easiest way to find this is to first reference the block diagrams on page 18 and 19, then find the relevant ICs on the schematic pages. You can then take the part numbers on the schematics and locate them on the PCB drawings located before the schematics.
Which pins handle the bass and treble frequency on IC400 And I would like to know how you figured that ic400 is the Pre-amp from service diagram
It is one complex product, that is why I said you needed the service manual. Everything looks to be handled by dedicated LSI (large scale integration) chips). It is hard to decipher it all but the audio processing appears to be done in IC 400, not that that helps much 🙁
According to the datasheet for the IC, none of the pins handle it (See attachment). The pre amp IC essentially only performs input selection and volume control. All EQ must be handled purely in the digital domain by the DSP, IC1501.
How I found it is I have looked at a lot of AVR service manuals so I knew basically where to look and knew what that IC was based on its name. But when I was first learning I would trace the signal from speaker outputs, back through the power amp, and then see what came immediately before the power amp. I would look up the IC data sheets to determine their functions (or look at the IC block diagram in the service manual).
@dkfan9 you could well be correct on IC1501🙂
Well tbh I looked at the block diagram and saw IC400 seemed to feed the power amp stages... but... having now seen the circuit I think that any attempts at swapping caps and so on will likely result in disaster, not that there are any obvious ones to swap as the processing is digital and not analogue.
What´s the supposed advantage of doing so, compared to the certain risk of butchering your amplifier?
Do you think it will "improve" anything?
1) that is an impressive piece of Engineering, do you think designers were morons who installed "bad parts"?
Those are HIGHLY rated Engineers, and certainly used well rated competent parts, do you think you will OUTSMART them after watching a couple snake oil YT videos?
2) in any case there is one Million parts there, thinking replacing a couple caps will do more than a drop of water in the Ocean is naïve (I would use stronger words but Moderators frown on that)
3) and those are flat response Analog parts, yet Audio thereb goes through more powerful Digital processors than Apollo 11 Space Travel computers (not kidding).
3) I REALLY suggest you paint ICs and caps with Audiophile Sound Improving Lacquer [tm]
Same effect, but MUCH safer, it damages nothing:
Thank You Sir I think things are different on home theater digital that everything is handle by ic pleasure god bless you sir