After some poking around I found that a voltage regulator on the processor/main board was getting very hot. It is a Toko 73400 and it did not produce any reasonable voltage at its output. I measured the output line against ground and it was short. Then I lifted the output pin and measured again. The short was on the IC. The plus line had no short. At least that was what I thought I had measured then...
Ordered 10pcs for little money from Aliexpress. Almost a month later, the chips arrived.
The chip had not been soldered to the pad properly. I applied solder to the pad with the iron and reflowed a new chip with hot air.
With great expectations I started the device. Nothing. Damned.
Measured again. There was still a short! It couldn't be the new regulator. More likely, I screwed up my first measurement. I started unplugging the many connectors one after another. It turned out that one connector was linking M-GND to GND. That shorted the regulator output to GND. There was a short between M-GND and the +7V line on the main board. M-GND had no connection to GND unless this connector was plugged in. I poked around to find something and after a while I hit the large black e-cap you see on the left side. It had the same reading against M-GND on both pins. This sucker did not look suspicious at all. No buldge. The ESR reading was good, because it had a short!
Ahhh, measurements...sometimes they are your enemy :-/
It was cheap crap of a brand I had never seen before. Shame on you, Sony! I replaced it with a decent Nippon Chemicon. This fault will never appear again!
The receiver is working all right again. Fixed for 3€ parts. In a repair shop, they would have swapped the whole processor board for a lot more bucks, if at all.
I am not entirely sure whether my first assessment of the regulator defect was right. Well, not much time and money wasted and a new one can't hurt, as it had to withstand a short. Now I have a batch of 9 adjustable, robust 1A, 1.3-12V low drop voltage regulators left. They might come in handy sometime.
Hello Hermann:)
ReplyDeleteI've got the same Sony and I'm in the middle of repair (it's rare and nice audio device). Unfortunately the class D amplifier is gone too in my. However I'm gonna replace it by another board. But nothing comes on amp input, I found out that PCM1681 that generates analog signal has +5V shorted to GDN. Thank you for sharing your knowledge :)
Best regards
Hi Pawel,
ReplyDeletewow, yours has taken a big hit then. Amp & DAC broken. I wonder what could have caused this widespread failure. I think the amp cannot kill the DAC and vice versa.
Good luck with fixing! And don't forget to swap this crappy capacitor in the main board :-)
Hi,
ReplyDeleteFortunately I found schematic for this device (I suppose that was probably broken by a storm).
When I started to repair, on one AMP output - there was strong DC about 15V. First I was trying replacing exotic mosfets IRF6665 by IRF640N (quite popular in DIY class D amp), but no success. Then I discovered no PWM on one output from IRS2052 (driver). That really sad - because this amp has extremely low THD distortion (that I've never seen in class D) and can handle up to 300W per channel.
Today I discovered (thanks to your blog) that DAC (PCM1681) has no analog +5V supply (no sound on AMP input). Having schematic I found LDO with short-circuit output to GND. I hope that I found cause not only effect.
repairing devices after storm is "very exciting" - you never know what next :D I have another SONY STR-DG510 - which now waits for new PCM DAC. It cost me a lot of time but I treats it as a kind of sport.
Of course I'll replace that capacitor.
bye
Pelos