Sony STR-DE445 did I get a faulty IC?

[goodpsusearch]

Hello, I got this AVR for cheap and tried to fix it as a fun and learning project.

First the audio video receiver would turn on but had no sound at all, but no "PROTECT" message.

So, I opened the metal case and noticed some marks showing that some liquid has been spilled on the amp. Those water marks were found on the main board and the digital board.

I disassembled everything, then checked every single cap on every board of the amp and recapped when needed.

Also fixed A LOT of cold solder joints and also done some modifications, I added heatsinks on linear voltage regulators, both on the main board and the digital board that were obviously overheating.

I also put a blob of thermal pad under the main board under the main IC201 sound processor because it also overheats.

After cleaning the pcb and doing all the above work I connected it and found that it now works except from the digital board.

When in 2 channel mode it works normally, checked all inputs and they all work and also checked all the amplifier outputs and they also work.

To check all the outputs used the 5.1 CH analog input that bypasses the digital board.

So everything works until I try to adjust the bass or tremble or enable a soundfield, then the amp goes silent.

Also the digital inputs don't work. But the dolby digital /DTS/PCM 48KHZ input data are properly recognized and shown on the display.

So, after doing some tests and examining the digital board schematic I concluded that the AK4527VQ was dead and ordered replacement from aliexpress. The replacement arrived and I soldered it on digital board but nothing changed. Does anyone know how to find out if I got a faulty IC and I should open a case on aliexpress or maybe I misdiagnosed the fault?

I can attach the service manual but it is really easy to find online, check first Google results.

The digital board of this amp is really simple due to cost cutting and very easy to understand. Can someone advise how can I rule out the replacement AK4527VQ being faulty?

I also have a digital oscilloscope and could use it if needed.

[CapLeaker]

Re: Sony STR-DE445 did I get a faulty IC?

If that particular IC seemed to be dead, I would look at VCC and MCLCK. If the clock signal isn’t there, the IC a would appear as dead, same if VCC is missing. There are other IC’s that work in conjunction with that particular IC. Sometimes there are IC’s that need to be flashed too… this being said, never buys just one IC, buy two… just in case one is dead… it does happen from time to time, even to very reputable large selling companies.

Your diagnosis does leave a clue since the digital stuff is properly recognized and displayed. I think you need to go back to the block diagram and poke around a bit more.

The DSP also has an SRAM, there are various voltage regulators etc… lots of things to check.
You changed the ad/da converter. Where as the problem you describing is more of a audio processing problem, since the amp clunks out also when you do other sound adjustments.

[CapLeaker]

Re: Sony STR-DE445 did I get a faulty IC?

Here is the service manual for that thing.

[goodpsusearch]

Re: Sony STR-DE445 did I get a faulty IC?

If that particular IC seemed to be dead, I would look at VCC and MCLCK. If the clock signal isn't there, the IC a would appear as dead, same if VCC is missing. There are other IC's that work in conjunction with that particular IC. Sometimes there are IC's that need to be flashed too… this being said, never buys just one IC, buy two… just in case one is dead… it does happen from time to time, even to very reputable large selling companies.

Your diagnosis does leave a clue since the digital stuff is properly recognized and displayed. I think you need to go back to the block diagram and poke around a bit more.

The DSP also has an SRAM, there are various voltage regulators etc… lots of things to check.
You changed the ad/da converter. Where as the problem you describing is more of a audio processing problem, since the amp clunks out also when you do other sound adjustments.

Hello.

I really appreciate your reply.

I checked every capacitor with ESR micro and Chinese transistor tester on the digital board and replaced the bad ones. I also put out caps that I had trouble testing them on pcb and tested them desoldered to be sure they are ok.

Τhen I checked all voltage regulators on digital board, those are 3 7805 and a 3.3V reg. All voltages were in spec, lowest was 4.8V for 5V. There is one extra 4.11Volt that is achieved with zener diode if I remember correct. Measured that one also and found it OK.

Then I had to exclude things from being bad using what I got from the receiver:

Since it is able to recognize when digital input is dts/dolby digital/pcm and it is able to show it on the screen, then IC1004 DIGITAL AUDIO I/F RECEIVER should be OK.

So, the bad IC should be IC1006 AUDIO DSP or IC1008 AUDIO CODEC or might be also the DSP RAM IC1007. I ruled out IC1005 CLOCK OSC and X1101 12.288MHz because they send pulses to DIGITAL AUDIO I/F RECEIVER that received optical / spdif in and that one we just proved above that it is working OK. If I am missing anything right now please let me know.


Next I tried to do some crude experiments that are shown better on the pics attached. My goal was to rule out/ find out the ICs at fault.

First I removed 3 100 ohm resistors, disconneting the 3 digital outputs of AUDIO DSP IC from the 3 digital inputs of CODEC IC digital to analog convertors (DAC).

Then fed the output of CODEC IC analog to digital (ADC) to each one of 3 inputs of CODEC IC digital to analog convertors (DAC), totally bypassing AUDIO DSP IC to rule out that this is the faulty one. But I didn't get sound

Also tried to connect the output of DIGITAL AUDIO I/F RECEIVER to each one of 3 inputs of CODEC IC digital to analog convertors (DAC), bypassing again AUDIO DSP IC with no sound.

Note that during the last experiment I was feeding optical in with PCM uncompressed sound.

[CapLeaker]

Re: Sony STR-DE445 did I get a faulty IC?

You have to keep in mind that there is not only one clock per IC, there are a few. The main crystal clock you can see with the oscilloscope. You should be also seeing data flinging around between the IC’s and other clocks. If the clock is screwed up the dsp, it won’t produce sound either. Keep on poking around…

[goodpsusearch]

Re: Sony STR-DE445 did I get a faulty IC?

Oh no


I feel so stupid now... The CNP103 connector was not fully inserted for some reason. It got partially out during troubleshooting or was not properly inserted in the first place.

The amplifier now works perfectly fine!

I get to set tremble/bass, enable digital effects like "HALL" , "JAZZ" etc, and of course tested it with dolby digital / dts source and it worked without any issue.

So the Chinese replacement CODEC IC was fine. Already left positive review for the item/vendor. That doesn't mean that the IC I bought is genuine but I could care less about that since it works.

While talking about AK4527, it should be noted that there is no way to know for sure whether the original AK4527 installed from the factory was indeed faulty or not, since I am not sure what happened to the CNP103 connector and it was not properly inserted.

There is a chance that the IC was good and the connector was out all that time.

It is difficult to notice the state of that connector because it is on the display board and it is hidden.

CapLeaker thank you so much for your valuable time.

[CapLeaker]

Re: Sony STR-DE445 did I get a faulty IC?

That happens even to the best of us. Great to hear you got it working!