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.
IC451 input to ground is open.
R455 is just around 14 ohm.
Something is failing when voltage is applied.
I may power it up and try it under power, pulling 1 component out at a time.
Cool.
Srinath.
R455 is just around 14 ohm.
Something is failing when voltage is applied.
I may power it up and try it under power, pulling 1 component out at a time.
Cool.
Srinath.
Hi,
What bother me it is that the voltage loaded from 13 volts to almost 2.0 volts and does not blow the fuse and not shorted.
What bother me it is that the voltage loaded from 13 volts to almost 2.0 volts and does not blow the fuse and not shorted.
Hi,
Just for the heck can you check the voltage at the fuse before the connector and after. I am still think the loaded to the PS should blow the fuse.
Just for the heck can you check the voltage at the fuse before the connector and after. I am still think the loaded to the PS should blow the fuse.
I suspect u have a dry (cracked) solder problem.
Thoroughly, solder the board first.
Some Qs...
How old is this. Was it kept powered through its life.
Post voltages on the diagram so that it is easy to diagnose.
Gajanan Phadte
Thoroughly, solder the board first.
Some Qs...
How old is this. Was it kept powered through its life.
Post voltages on the diagram so that it is easy to diagnose.
Gajanan Phadte
Last edited:
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,
First " HAPPY NEW YEAR " to every body. Yes I have another suggestion. Next time please remove the fuse and check the current across the fuse contacts. This way we will find out why the fuses does not blow and how much current the circuit it is using.
First " HAPPY NEW YEAR " to every body. Yes I have another suggestion. Next time please remove the fuse and check the current across the fuse contacts. This way we will find out why the fuses does not blow and how much current the circuit it is using.
Its 4:40 pm and it looks like midnight ... and its been the brightest it has been all day.
Cool.
Srinath.
Cool.
Srinath.
Across the fuse terminals - I see 72 or so in the 200u setting in the DCA part. So does that mean I have 72 microamps ? Now in the 20m setting, I get .5 - so its a .5 milli amp ? So its a low amperage draw.
I am going to check the rest of the things you mentioned.
Cool.
Srinath.
I am going to check the rest of the things you mentioned.
Cool.
Srinath.
Removing d453 the pin 4 voltage goes up to 5.6v from 5.45.
I then put d453 back and removed d454, 455 ,456 and 457 - the 4 that are the rectifier bridge. The voltages all dropped to 0, pin 6 and pin 2 went to 0.
Cool.
Srinath.
I then put d453 back and removed d454, 455 ,456 and 457 - the 4 that are the rectifier bridge. The voltages all dropped to 0, pin 6 and pin 2 went to 0.
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.
Hi,
One more thing can you check in the service manual if it have the specs for the transformer. It may have it.
One more thing can you check in the service manual if it have the specs for the transformer. It may have it.
The relays are 12vdc. You think the transformer puts out voltage, but cant put out current ?
I am thinking I may have a similar transformer somewhere ... but its not a big transformer, cant be that $$$.
Cool.
Srinath.
I am thinking I may have a similar transformer somewhere ... but its not a big transformer, cant be that $$$.
Cool.
Srinath.
If I shorted the relays, I wont be needing the little transformer - if it is the only issue ... of course I wont have the display. But let me find the right trafo - is a CD player transformer the right voltage ? 12v ?
Cool.
Srinath.
Cool.
Srinath.
Hi,
You do not want to do that. They are using them in the power up sequence. Up to now I think the transformer it is gone.
You do not want to do that. They are using them in the power up sequence. Up to now I think the transformer it is gone.
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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