Sony HCD-MJ1 receiver died on me while on standby

[Nigel Goodwin]

What about across CN801 pin 1 to pin 2? - it should read13.3/4 or so, as the above readings.

 

[Jean-Pierre]

Yes it does. 13,4.

 

[Nigel Goodwin]

Then we've wasted 20 posts - there's nothing wrong on the primary side of the transformer, the fault must be elsewhere.

I presume you can't eject the DVD draw?, and that you've tried turning it ON? - it's not just the display that's stopped working (a common fault).

 

[Jean-Pierre]

Wasted ? Not at all. I,ve learned a lot. I repaired my multimeter and learned to use it. Before I only did DC voltages. Before I started the repair, nothing moved, not the DVD-tray, not the MD-tray and for sure not the display. As I wrote before, it died quietly while on standby.
I’ll put it back together and plug it in the mains and see what happens.
Thanks for your help.

 

[Nigel Goodwin]

With it all reconnected try measuring the DC voltage on pins 9 and of IC821, pin 9 should be 5.8V and pin 10 should be 8V. Pin 9 is the power to the main micro.

 

[Jean-Pierre]

OK, I'll do that. But the transformer has got only 9 pins going out. I'll to get earth somewhere and try to get a reading.
When I plug the mains a hear a faint click, so something get power.
And when I unplug a second click.

Is this the clicker ??

 

[Jean-Pierre]

Stupid me. Instead of verifying the IC821 on the schematic I bought of the transformer.
But now I see what you are pointing at : the rectifier .
I am reading a book on the discoveries of Nikola tesla and I should have known that AC is transformable, but still stays AC .......
Forgive me.

 

[Jean-Pierre]

Wat is trivial for you, is mucho for me. I'll measure and report back.

 

[Jean-Pierre]

No sign of life, no voltages. No juice....

 

[Jean-Pierre]

But D801 gives 35 volts ....

 

[Nigel Goodwin]

Try on CN101 (lead from transformer) pins 3 and 4, should be 10V AC on those pins.

 

[Jean-Pierre]

Yes, 12 V AC.

 

[Nigel Goodwin]

The voltage from there goes through a pair of circuit protectors (small soldered in plastic fuses) ICP821 and ICP822, you can test those without power with your low ohms range.

 

[Jean-Pierre]

OK, ill do that. If they are interrupted can I bridge them safely ?

 

[Jean-Pierre]

ICP821 gives 5,65 M Ohm and ICP822 gives 0,001 Ohm.

 

[rjenkinsgb]

You can bridge the failed one with an equivalent fuse - or preferably test the components after that to find the cause of the failure.

Simply bridging it out now is likely to cause more damage, as there will no no overcurrent limiting if there is a fault in whatever that feeds.

 

[Jean-Pierre]

Yes, caution is good advice. I’ll get a replacement fuse first. But upstream there is nothing else but the transformer, so could the one out of two similar fuses have blown because of a spike, or fatigue ....

 

[Les Jones]

I would suggest connecting a 12 volt (Filament.) bulb such as a 21 watt car stop lamp bulb in place of the fuse while continuing to trace the fault. (Avoid using a 20 watt quartz halogen type bulb as these have very low cold resistance.) Before doing that it would be worth testing for a short circuit on the 4 diodes in the bridge rectifier using the diode test setting on your meter.

Les.

 

[Jean-Pierre]

Good morning Les, I have a small dashboard bulb of a few watts, could that do ? Checking the diodes on the rectifier is beyond my capabilities. If I replace the fuse and switch on ??

 

[Jean-Pierre]

In my limited imagination I see cause of the blown fuse upstream. The main glass fuse on the 220 mains input was never blown. This is a small soldered on fuse immediately behind the transformer, I think, before the rectifier. If I talk nonsense, forgive me.