All
I have a Sony HCD-SPZ1 Micro System which is in need of repair and I need your help. Bit of background, I bough this amp for almost nothing from someone who was about to dump it. The reason i bought it is because I already have a similar style amp by Sony and once you change few capacitors in signal path it sounds amazing with any good set of speakers.
Now to the problem, owner said the amp use to shut down every now and then but will turn back on afterwards. As it stand now when I plug it in it shows the display screen lit up but when i push the power button on it comes on for say 3 seconds and shut itself down with power led blinking and the lcd display turned off altogether. If I unplug it and re-plug it the same happens again.
To me it feels like the DC protect system is kicking in. I have tested few transistors that make up the DC protect circuit but they all seems ok. What else could be wrong with it? I am no expert in electronics but I can check and replace components if needed.
Oh and one more thing if I unplug the power to Amp section it all turns on fine. So issue is somewhere in the Amplifier section. Should I assume the Amp chip is dud and causing DC detect to trip or is there anything else I can check before I dump it (which i really don't want to). Also I had a feeling it is something else as it was a gradual fail rather than instant fizz.
Any help or guidance on where to look for etc will be much appreciated. Attached Amplifier circuit (Page 33) and Relay on off system controler (Page31) for information.
I have a Sony HCD-SPZ1 Micro System which is in need of repair and I need your help. Bit of background, I bough this amp for almost nothing from someone who was about to dump it. The reason i bought it is because I already have a similar style amp by Sony and once you change few capacitors in signal path it sounds amazing with any good set of speakers.
Now to the problem, owner said the amp use to shut down every now and then but will turn back on afterwards. As it stand now when I plug it in it shows the display screen lit up but when i push the power button on it comes on for say 3 seconds and shut itself down with power led blinking and the lcd display turned off altogether. If I unplug it and re-plug it the same happens again.
To me it feels like the DC protect system is kicking in. I have tested few transistors that make up the DC protect circuit but they all seems ok. What else could be wrong with it? I am no expert in electronics but I can check and replace components if needed.
Oh and one more thing if I unplug the power to Amp section it all turns on fine. So issue is somewhere in the Amplifier section. Should I assume the Amp chip is dud and causing DC detect to trip or is there anything else I can check before I dump it (which i really don't want to). Also I had a feeling it is something else as it was a gradual fail rather than instant fizz.
Any help or guidance on where to look for etc will be much appreciated. Attached Amplifier circuit (Page 33) and Relay on off system controler (Page31) for information.
But he's right. The behaviour is exactly what's to be expected if one of the rails failed -> power supply. Everything after that is the power amp ICs. Oh, and the M30624MGP-A41FPU0 main IC isn't available anymore anyway either, so that's all you can do.
Thanks guys. So I checked the smpsu section today and somehow the 28 volt rails are only showing 24v and 16v rail is only showing 12v. Could this be the reason? Is the this normal behaviour of smpsu under no load? What parts could have gone in smpsu to cause it.
No, that's not normal. But that should still be within the error margin, most ICs have a wide range of voltages they can be used. But if it differs that much if idle, what will happen once you put load on them? I think that might then the reason for it to fail. Why don't you try it with an external power supply?
ICG thanks. I don't have any other spare supply lying around. Now I was thinking to use the power supply of my existing working system but I am afraid if I mess my working system trying to revive this bugger
ICG I have never tried that before. Could you please explain how to go about it. The rails are 28 - 0v and 16 - 0v
Simply put, wire resistors across the rail voltage to 0V and observe the voltage and current. I'm sorry, but I have to say, if you need an explaination for that, I doubt you are able to do the repair. The switching power supply contains dangerously high, potentially lethal voltages. And that is NOT an exaggeration!
ICG I understand your concern but we all have to start somewhere. I will see if I can manage something like that. It will be difficult as everything is surface mounted and miniature. I am at work at the moment. I will have a go at it again over weekend and report back.
I found 2 open resistors on psu but as they were smd type they were nightmare to deal with. Most of transistors and caps are smd type as well. The resistors were like the size of half a rice. I am not planning on wasting any more time on it. Thanks for your suggestions everyone. This is going in the recycling bucket.
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