Oh no...... oh help me..... it's JUNK CONSUMER ELECTRONICS REPAIR TIME again !!!
A friend just bought me this compact "retro looking" stereo system. These things are trendy I am starting to gather. It's a good friend and I owe him much, so I must absolutely go the extra mile to fix this thing.
Plus, it comes from his wife's work place. she works in my village's retirement home. She uses that thing to entertain the elderly. They are not allowed to use the thing, normally it's her that operates the stereo. Also, it appears it still available for sale currently, and for whooping 120 freaking Euros ?!
That's a lot for something that's worth 2 Euros tops to me... if even that.
So, a nearly new 120 Euros unit, that's extra motivation for this rescue mission.
She said that the problem is that when she puts a USB stick with MP3 files on it, it doesn't work anymore. Just nothing happens, as if she hadn't inserted the stick. I confirm that.
There is also an SD card reader with the same purpose... so I put some MP3 files on an SD card and... same result, nothing happens.
The controls aren't exactly intuitive, to me at least.. I never find consumer electronics intuitive, there UI never "speaks" to me somehow
So to make 100% sure it was not an operator error, I searched for the user manual... no luck.
It's sold under the distributor/ retailer's own "brand" : " essentielb ". No typo. the trailing 'b' stands for " Boulanger ", the name of the distributor. Model " Madison BT ".
while failing to find a user manual for it, Google did find something else that was interesting : the manual for a JVC RD-F327 that, although has slight UI difference : top row of buttons merged with the bottom row, plus they added a remote control capability, that's about it. Clearly the same unit. So the manual says that in order to read MP3 files from an SD card or USB stick, all you have to do is select SD or USB, simple enough, then insert the media and that's all, it should start playing music automatically, no need to press any button.
So clearly, it doesn't work. The fact that both the SD card and USB don't work, would suggest that the problem is common to both, rather both having their own failure. So obviously they have in common the CPU.. which runs fine since the stereo works just fine others than USB and SD cards. So either some I/O in the CPU are fried somehow. Or maybe the SD and USB are not wired wired straight to the CPU and there is some discrete components involved. Problem is, no schematic.
Oh forgot to say. USB and SD connectors are soldered directly to the main CPU board, close to the CPU. So there is no interconnect problem here.
Also, the USB stick I used happens to have an LED built into it, that flashed when there is activity.. and that LED is dead as a dodo.
So I am thinking that the problem might be that the stick and SD card are simply not detected at all and the CPU is therefore not even trying to communicate.
But again I don't know how these things work and no schematic, so no idea what to probe, what supporting external components there might be around these connectors, aside from the CPU per se.
Luckily the main board is fairly easy to remove / work on, once you remove the turn table assembly and the CD player transport, and cut some cable ties and remove lots of plugs... so at least I can do a close inspection of the board, try to trace signals, scope things, inspect solder joint, solder stuff.... I can work on that board. So it's not totally hopeless.
Below a High-res pic of the board, 5MP, for the good cause, in case someone catches on something. I asked for a derogation for this one 5MP pic, of course. Still I compressed it, so "only" 1MB or so.
Any help welcome... if you can find schematics for this thing, or know how a USB connector and SD card might be wired to a CPU... what supporting discrete components that might need, that might fail... I am all ears.
In the meantime I will stat digging...
Power supplies : unit gets 12V DC from an external brick. Then there is a tiny power board at the back of the rear panel that carries a 7805. The 5V and 12V are then sent to the main CPU board. On that board I see another regulator, a 78M06. So the board has 5V, 6V and 12V.
I checked the main 12V supply at the barrel, it's fine. Need to check 5V and 6V now, but I am not expecting them to be bad... at least not the 5V or else the freaking CPU would not even work.
CPU BTW is an " ALI M5675 A1 ".
I will search for the datasheet see how if they give a typical wiring schematic for the SD card and USB... but I doubt it would involbe an additional 6V supply. So I don't think it's as easy as a dead supply. I fear a fried I/O in the CPU, hence not repairable...
Thanks for your attention, for the one or two that read all that.