IC451 output to ground - flashes 120 or so and open, like a capacitor would.
After removing fuse f453 from FC454 to ground - open.
T451 pin 2 to ground - open.
Across c462 flashes a resistance and then open. Either side of it to ground, also open.
Removing F453 and across pin 1 and 2 of T451. I read about 3.5 ohm.
My theory - Bad D458. These all seem to check out fine I think.
Or a bad D453. But I cant see that and getting any voltage to pin 2. Maybe It isn't passing proper 1/2 wave rectified ...
OK so my assumption is this - ac @ F454 should get 1/2 wave rectified with D453, R453 cuts it down a bit, then the cap c465 smoothes current, the D458UZ5V1 regulates voltage, and the R454 bleeds a little off it leaving proper smooth and steady 6v @ pin 2. I have 2.82. Since I cant measure ripple or nothing ... I dunno, maybe c465 or r454 bleeding too much.
No clue, I am confused.
Cool.
Srinath.
After removing fuse f453 from FC454 to ground - open.
T451 pin 2 to ground - open.
Across c462 flashes a resistance and then open. Either side of it to ground, also open.
Removing F453 and across pin 1 and 2 of T451. I read about 3.5 ohm.
My theory - Bad D458. These all seem to check out fine I think.
Or a bad D453. But I cant see that and getting any voltage to pin 2. Maybe It isn't passing proper 1/2 wave rectified ...
OK so my assumption is this - ac @ F454 should get 1/2 wave rectified with D453, R453 cuts it down a bit, then the cap c465 smoothes current, the D458UZ5V1 regulates voltage, and the R454 bleeds a little off it leaving proper smooth and steady 6v @ pin 2. I have 2.82. Since I cant measure ripple or nothing ... I dunno, maybe c465 or r454 bleeding too much.
No clue, I am confused.
Cool.
Srinath.
Really I am confused. All the resistance checks does not showed a short. Right now the only that can load the voltage is the IC451. Can you check resistance from the input to ground. Also last results can you lift the resistor R455 or it get hot. The reason I do not belief that diode D453 it is causing any problem is that the R453 is 4700 ohms. If you divide the voltage 18 volts /4700 = .003 amps. It will no load the PS.
Hi,
I double checked the schematic and found that the only thing that can load the voltage low is by the diode D4554, diode D456 or the IC451 short when the voltage it is applied. If one of the 3 shorted will take the voltage low. If you follow the voltage thru the circuit there is nothing else that can loaded the voltage other than the above mention.
The other path it is thru the IC451 and D459 and then the micro loading the voltage. But the voltage at the D459 anode is 2.8 volts and the cathode is at 5.8 volts that will eliminate the micro. The question I have is why the fuse does not blow. The fuse it is 500ma and if you load the voltage from 18 volts to 2 volts it should blow the fuse and the fuse check OKAY. Resistance check does not showed any short. I ran out of suggestion.
I double checked the schematic and found that the only thing that can load the voltage low is by the diode D4554, diode D456 or the IC451 short when the voltage it is applied. If one of the 3 shorted will take the voltage low. If you follow the voltage thru the circuit there is nothing else that can loaded the voltage other than the above mention.
The other path it is thru the IC451 and D459 and then the micro loading the voltage. But the voltage at the D459 anode is 2.8 volts and the cathode is at 5.8 volts that will eliminate the micro. The question I have is why the fuse does not blow. The fuse it is 500ma and if you load the voltage from 18 volts to 2 volts it should blow the fuse and the fuse check OKAY. Resistance check does not showed any short. I ran out of suggestion.
The Reciever is about 11 years old, it worked as a 2 channel receiver, not as a surround amp, I found and replaced swollen caps on the dolby board after which it didn't power up. It actually powered up without the dolby board in ... but didn't after replacing the caps. The thing had to have been left idle for a few years before I got it ~2 months ago.
I will test these later today, too much celebratin for 2013, and thanks guys and wish you all a very happy 2013.
I will actually get some ground wire made up, so I can power up the receiver with the board outside, so I have access to testing the board with it powered up.
Is it possible that as the transformer has an internal short when it is warm ? Of course that would soon after fry itself into a goo ...
Cool.
Srinath.
I will test these later today, too much celebratin for 2013, and thanks guys and wish you all a very happy 2013.
I will actually get some ground wire made up, so I can power up the receiver with the board outside, so I have access to testing the board with it powered up.
Is it possible that as the transformer has an internal short when it is warm ? Of course that would soon after fry itself into a goo ...
Cool.
Srinath.
Hi,
The current it is too low. It looked like the transformer is gone. Lets try one more test. Assuming the DC voltage it is 20 so if you solder a 200 ohms resistor to the load side of the fuse and ground you should read 100 ma. It does read read not 100 ma the transformer it is bad. One more thing does the relays have the specs written on top of the relay or the side? That will tell you the voltage of the transformer.
The current it is too low. It looked like the transformer is gone. Lets try one more test. Assuming the DC voltage it is 20 so if you solder a 200 ohms resistor to the load side of the fuse and ground you should read 100 ma. It does read read not 100 ma the transformer it is bad. One more thing does the relays have the specs written on top of the relay or the side? That will tell you the voltage of the transformer.
I cant see it in the schematic - T451 J2812220023X TRANS 120/60 ST-BY <- Has no voltage mentioned.
But since 1 part is regulated by a 5v zener, and the other leg is regulated by a 7806 - is it a decent assumption it is a 12v ac output, and has that split into 2 via c463 and 464 ?
Cool.
Srinath.
But since 1 part is regulated by a 5v zener, and the other leg is regulated by a 7806 - is it a decent assumption it is a 12v ac output, and has that split into 2 via c463 and 464 ?
Cool.
Srinath.
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