Aiwa NSX - R51 repair NEED HELP!!

[tautvydas200]

Hello,
My old music center broke down when my brother accidentally hit it with his foot. Model is Aiwa NSX - R51. I'm kind of new in electronics. In my free time I can easily repair power supplys and other stuff. But this machine is like my kryptonite I'm stuck with it. Can some one show me the way to find problem? This music center doesn't show any sign of life. Power reaches microcomputer. I have found some solder joint cracks and repaired them.

Service manual http://diagramas.diagramasde.com/audio/NSX-R50%20sm%20data.pdf 

Photos https://drive.google.com/folderview?id=0B-rZHVpfb8F1TjdJTkl1bEtQU2M&usp=sharing

Thanks for help! And sorry for my bad english.

[Agent24]

I see solder bridges on some pins on IC901 for a start. Did you do that? Did you clean those up before you applied power?

[tautvydas200]

Yes I have cleaned those.

[Agent24]

More detail as to what you have measured and where, is needed.

What voltage did you measure, and on which pins of IC901?

[tautvydas200]

Reset 5,02 V
19 pin 5.13 V
41 pin 5.11 V
80 pin 5.02 V
Also V-STBY on connector to this board is 13.23 V. It should be if on 11.3 V or if off 12.54 V

[Agent24]

I wouldn't worry about that V-STBY too much. It's coming straight off a transformer and the voltage will be higher if your line voltage is higher than the nominal 230v.

Does IC901 /RESET line go low briefly at power on? (It should)

Does IC901's VDD1 and VDD2 at Pin 37 and 79 have 5v?

Is the clock running? Should get 4.19MHz at pin 38\39.

[tautvydas200]

79 pin 5,12V
37 pin 5,12V
When I push power button reset line stays at 5,02 V
I don't know how to mesure clock signal. I only have multimeter.

[Agent24]

Power button seems to be soft-power controlled by IC901 so unless the IC is running the power button won't do anything.

You'd need to check the /RESET line stays low for a certain time when mains power is applied, but without logic analyser or DSO you can't do that really.

Not sure how you can measure the clock with your DMM. Maybe check DC voltage and if you get something about 2.5v it might be working, if you get 0v or 5v it maybe not running, or the meter is loading it down. You really need a scope to check that.

[tautvydas200]

So ok I will try to find scope to borrow. Also can you explain me why is there HOLD line and what it actually do?

[Agent24]

I'm pretty much guessing here... but I think it's part of the AC\DC detection function?

Pin /I-HOLD on the CPU maybe means Input-HOLD, eg: prevent buttons from functioning while the pin is low. What voltage is on that pin?
Or maybe I just means it's an input pin (schematic symbol > on pin confirms this) and it's for the HOLD function.


See above the " -12- " marking on page 12 schematic where it says "AC & DC DET"

/HOLD line seems to be controlled by Q060 on other board, which seems to be controlled by  Q061\Q062. It looks like these are controlled via several different inputs, including something from AC supply via D063 and D064.
it may also detect faults via Q063 and Q064, one of their inputs trace back through D062 and D065 to the speaker outputs, and also thermal protection via Q059 and TH101\TH102 on the output transistors.

So perhaps your fault detect circuit is faulty. Check for more dry joints etc perhaps in those areas.

[tautvydas200]

HOLD I measured from IC901 is 3.43 V
Also look in the middle of main board page at page 12. There is written VCC 11.1 V.
I measured at Q126 and C133 and voltage is 0 V. Is it normal or not?

[Agent24]

Vcc 11.1v rail looks like it's derived from the 12v standby rail through Q009 etc (just above and to the left of the AC\DC Det circuit page 12)

So if you are getting 0v on Q126\C133 (I assume you mean Q126 emitter?) then maybe Vcc 11.1v rail is down. If it is, check Q009 and associated components, and make sure the STBY rail is getting to Q009 too.