Good afternoon my friends,
I have a power supply mark NORTEL it has two bridge rectifiers one is small and the other is big.
Kindly can anyone explain why they use this method?
also, I was wondering that they use just the positive lead from the small bridge to supply LMC6042 also to supply 74AC00 and the negative lead is not connected to any point ( I thought there was VIA ) from the back .....but nothing ( it is not connected at all). I was wondering how to complete the circuit ( the return line to bridge to negative lead).
and for the IC 74AC00 the VCC on pin 14 is coming from the small bridge but the ground (- ) is connected to the big bridge.
Please can anyone explain to me this circuit how it works

 

Please can anyone explain to me this circuit how it works

It would help if you posted a schematic. If you can't find one, trace the relevant circuitry and make one.

 

You may not like my answer but my advice is to cease investing your time in this badly damaged PS and redirect your energies to finding a suitable replacement. Power supplies like this are both cheap and hard to repair (other than replacing the bad capacitors), making them a very poor candidate for a DIY repair job.

 

It would help if you posted a schematic. If you can't find one, trace the relevant circuitry and make one.

thanks sir, it looks a good idea.....sure I haven't the schematic.
but I was wondering why he used a two bridge and from the small bridge he used just the positive lead.
best regards

 

You may not like my answer but my advice is to cease investing your time in this badly damaged PS and redirect your energies to finding a suitable replacement. Power supplies like this are both cheap and hard to repair (other than replacing the bad capacitors), making them a very poor candidate for a DIY repair job.

thanks sir, I really appreciate your advice.
and as you read my questions. I'm trying to understand the perspective of the designer.
especially why he used the two bridges and why he just used one lead from the small bridge ( positive lead ).
best regards

 

D1 bridge is on the hi voltage mains side, the main power rectifier.
D16 is probably not on the mains but low voltage control circuitry and it may be just a handy way to use 2 diodes, not the full bridge.
Without a circuit it will be very hard to determine the actual function.

I echo @wayneh in his comment. Do not try to fix this. These power supplies are lethal and from your question, it is fairly plain you are an electronics novice.
Electronics is a great hobby and/or career. I have been involved if it for almost 60 years. We would like to keep you safe so please do not try to fix this but stick to low voltage devices for your own safety.

 

D1 bridge is on the hi voltage mains side, the main power rectifier.
D16 is probably not on the mains but low voltage control circuitry and it may be just a handy way to use 2 diodes, not the full bridge.
Without a circuit it will be very hard to determine the actual function.

I echo @wayneh in his comment. Do not try to fix this. These power supplies are lethal and from your question, it is fairly plain you are an electronics novice.
Electronics is a great hobby and/or career. I have been involved if it for almost 60 years. We would like to keep you safe so please do not try to fix this but stick to low voltage devices for your own safety.

Good morning sir,
thanks for your advice, it really precious to me.

 

It looks like a switch mode power supply. Your first 2 pictures show the board with the high frequency transformer missing. Can you explain why this has been removed ? These transformers very really fail and if it has failed there is almost no chance of getting a replacement as they made to order for a particular design of power supply.

Les.

 

It looks like a switch mode power supply. Your first 2 pictures show the board with the high frequency transformer missing. Can you explain why this has been removed ? These transformers very really fail and if it has failed there is almost no chance of getting a replacement as they made to order for a particular design of power supply.

Les.

Good evening sir,
Acutely I just removed it to trace the lines. The transformer is working I tested it with LCR meter on 100KHZ .
And it is a power supply this is the name of it.NORTEL

 

I would have started by replacing all the electrolytic caps. C16 even looks a little bulgy to me but it's hard to tell from a photo. Anyway they can fail without any change of appearance.

 

I would have started by replacing all the electrolytic caps. C16 even looks a little bulgy to me but it's hard to tell from a photo. Anyway they can fail without any change of appearance.

thanks sir,
Noted I will try to change it and see what will happened.