Who Can Read a Circuit Board ?

[Nilesh]

On this pic, I see what I think are 3 connections on that PCB from the old transformer. Are those the outputs (secondary windings)? The connection on the right has a + sign a little further up the trace. Is there a - a little further up the trace for the LEFT connection in that pic? And, perhaps a symbol for ground on that middle connection trace?

EDIT: Now that I zoom and look closer, that + sign that I see may just be polarity markings for diodes, so I may be on the wrong track with the above comments.

Okay , what i will tell you is that on this photo
http://i66.tinypic.com/ric27k.jpg
The cable soldered are powering the subwoofer but what is wrong is that there is static noise( current noise ) being carried to the speakers . Which means that the cable has been wrongly soldered .
If i mark the mains entry (onboard ) , will you be able to trace the transformer primary windings ? As to my point the mains entry on the board is like isolated on the board.It does.not have any route from that part ...Do i send it ?

 

[slipperybidness]

No , its difficult to get these type of transformer .The ones that get soldered directly onboard :/ .
Yes , the old transformer had multiple taps on the outputs .

OK. Well, we may be starting to make some sense here, but you may not have the transformer that you need.

The old transformer--It has 1 set of primary windings (i.e. 2 cables on the primary side)? How many sets of secondary windings does it have (i.e. how many output taps)?

So, if a transformer has multiple output taps, then the most likely scenario is that the output is putting out multiple voltages for different parts of the circuit, or to different PCBs. BUT, that may not be guaranteed. Some transformers have multiple output taps simply to allow flexibility on how they are wired. But, in your case I am beginning to suspect that you have multiple secondaries that are supplying multiple output voltages (like maybe 12V, 5V, 3V or something similar). Does that seem to be true?

The problem is that your NEW transformer has a single output tap that supplies 12V. You see the problem here?

But, let's make an assumption that you have the proper transformer (and that may be a very big assumption at this point).

If you have located the mains line inside the chassis and have connected that to the primaries on the new transformer, then you have at least connected the input of the transformer to the correct connection. Hopefully this isn't directly connected to the mains line, but rather connected to the mains through the power switch and the fuse.

Now, let's focus on the output. The output of a transformer should be going to your bridge rectifier. A rectifier is a set of diodes that will convert an AC signal into a DC signal. Typically the output of the rectifier will be going over to some power filter capacitors, and the filter caps are typically the largest (electrolytic) caps in the entire chassis.

Can you locate your bridge rectifier in the Power Supply? If you can find that, then you should be able to trace that back on the PCB and see exactly where that connects to the output(s) of the transformer. Since your old transformer has multiple output taps, you may have more than 1 bridge rectifier.

Now, what does a bridge rectifier look like? It will either be 4 discreet diodes connected in a diamond pattern, or it will be a single IC.

This schematic should make it clear as to how the transformer connects to the rectifier:

I'm guessing here, but I would think that you would more likely have an IC rectifier instead of a discrete rectifier. An IC rectifier will likely look like one of these pics. Dunno which one you may have, and if it is Surface Mount then it may be tough to find.
https://www.google.com/search?q=discrete+bridge+rectifier&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjt4P7v-fvTAhXrwFQKHX1dDdIQ_AUICygC&biw=1280&bih=827

This is a general schematic of a power supply, this should help to visualize everything I'm trying to tell you. Can you study this schematic and find the corresponding components in your gear?

 

[highfigh]

This is a classic case where using the original part is the best way to go. When someone without experience tries to repair something, this is a common result.

 

[slipperybidness]

This is a classic case where using the original part is the best way to go. When someone without experience tries to repair something, this is a common result.

Agreed!

The only problem is, if you are always scared to get your hands dirty and scared to break things, then you never gain the valuable experience that you need for the next time.

Unfortunately, you must understand that sometimes the education is that you learn what NOT to do

My philosophy is typically "it's already broken, I probably can't break it any worse".

Now, at my job in an analytical lab at a semiconductor manufacturing plant, we may be talking about a $300k piece of equipment. Yes, I have made mistakes that cost us $5k+! But, in the long run I have saved the company many hundreds of thousands of dollars over the years. Just consider a mistake like that a quick $5k education

 

[Nilesh]

OK. Well, we may be starting to make some sense here, but you may not have the transformer that you need.

The old transformer--It has 1 set of primary windings (i.e. 2 cables on the primary side)? How many sets of secondary windings does it have (i.e. how many output taps)?

So, if a transformer has multiple output taps, then the most likely scenario is that the output is putting out multiple voltages for different parts of the circuit, or to different PCBs. BUT, that may not be guaranteed. Some transformers have multiple output taps simply to allow flexibility on how they are wired. But, in your case I am beginning to suspect that you have multiple secondaries that are supplying multiple output voltages (like maybe 12V, 5V, 3V or something similar). Does that seem to be true?

The problem is that your NEW transformer has a single output tap that supplies 12V. You see the problem here?

But, let's make an assumption that you have the proper transformer (and that may be a very big assumption at this point).

If you have located the mains line inside the chassis and have connected that to the primaries on the new transformer, then you have at least connected the input of the transformer to the correct connection. Hopefully this isn't directly connected to the mains line, but rather connected to the mains through the power switch and the fuse.

Now, let's focus on the output. The output of a transformer should be going to your bridge rectifier. A rectifier is a set of diodes that will convert an AC signal into a DC signal. Typically the output of the rectifier will be going over to some power filter capacitors, and the filter caps are typically the largest (electrolytic) caps in the entire chassis.

Can you locate your bridge rectifier in the Power Supply? If you can find that, then you should be able to trace that back on the PCB and see exactly where that connects to the output(s) of the transformer. Since your old transformer has multiple output taps, you may have more than 1 bridge rectifier.

Now, what does a bridge rectifier look like? It will either be 4 discreet diodes connected in a diamond pattern, or it will be a single IC.

This schematic should make it clear as to how the transformer connects to the rectifier:

I'm guessing here, but I would think that you would more likely have an IC rectifier instead of a discrete rectifier. An IC rectifier will likely look like one of these pics. Dunno which one you may have, and if it is Surface Mount then it may be tough to find.
https://www.google.com/search?q=discrete+bridge+rectifier&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjt4P7v-fvTAhXrwFQKHX1dDdIQ_AUICygC&biw=1280&bih=827

This is a general schematic of a power supply, this should help to visualize everything I'm trying to tell you. Can you study this schematic and find the corresponding components in your gear?

I firgured out the sitting of the Secondary Windings . (like in the photo i have sent , where the RED & RED & Black Cable was soldered ) .
The subwoofer is powering on( music plays from 3.5mm Jack) but what is wrong is that there is static noise( current noise ) being carried to the speakers . Which means that there is some walk around here . Now what we need to know is what is bringing Volts to the audio line . I checked the 3.5mm jack , 3V is coming along it .

 

[slipperybidness]

I firgured out the sitting of the Secondary Windings . (like in the photo i have sent , where the RED & RED & Black Cable was soldered ) .
The subwoofer is powering on( music plays from 3.5mm Jack) but what is wrong is that there is static noise( current noise ) being carried to the speakers . Which means that there is some walk around here . Now what we need to know is what is bringing Volts to the audio line . I checked the 3.5mm jack , 3V is coming along it .

When you say you "checked the volts of the audio line"--You need to provide a whole lot more info here!

Did you "check the volts" with a volt meter? Was the meter set for VAC or VDC? Or, did you "check the volts" with an oscilloscope and see 3VAC or 3VDC?

Were you playing music when you did this voltage check? What happens if you repeat the measurement with no music playing, but everything powered up?

Your audio line should have some voltage while it is playing music, voltage IS the audio signal. Now, if you have a constant 3VDC offset on your audio input, then you have some SERIOUS problems here!

 

[Nilesh]

When you say you "checked the volts of the audio line"--You need to provide a whole lot more info here!

Did you "check the volts" with a volt meter? Was the meter set for VAC or VDC? Or, did you "check the volts" with an oscilloscope and see 3VAC or 3VDC?

Were you playing music when you did this voltage check? What happens if you repeat the measurement with no music playing, but everything powered up?

Your audio line should have some voltage while it is playing music, voltage IS the audio signal. Now, if you have a constant 3VDC offset on your audio input, then you have some SERIOUS problems here!

Checked With Voltmeter on AC Mode .
In fact i checked for this Off the 3.5mm Jack Line Itself With No Music Input . And , if i connect the jack to my phone , it disturb the phone which i suppose is the cause of the 3V coming along the line .

 

[highfigh]

Agreed!

The only problem is, if you are always scared to get your hands dirty and scared to break things, then you never gain the valuable experience that you need for the next time.

Unfortunately, you must understand that sometimes the education is that you learn what NOT to do

My philosophy is typically "it's already broken, I probably can't break it any worse".

Now, at my job in an analytical lab at a semiconductor manufacturing plant, we may be talking about a $300k piece of equipment. Yes, I have made mistakes that cost us $5k+! But, in the long run I have saved the company many hundreds of thousands of dollars over the years. Just consider a mistake like that a quick $5k education

So, have you ever wanted to open that $300K piece, just to see how it was made? Not even little? Maybe just once? What could it hurt? C'mon! It'll be like driving into Wisconsin!

I agree with your comment about exploration, but it's best to look at what is there and where things go before starting. Have I done the opposite? Absolutely! I learned that a switch wired across the how and neutral to an amplifier makes the fuse die and when I wired something to a hot outlet, I made a fine wire stripper out of the cutting edge on a needle nose pliers. Well, that's what I told my dad, anyway.

The fact that this transformer has short legs that pass through the PCB is what would have told me to get the OEM part.

 

[TLS Guy]

I sell smoke in the offing.

Your pictures have vaporized by the way, like that circuit board will when you are finished with it.

I did see the pictures before they vaporized.

The transformer you are trying to use is clearly in no way similar to the one you removed. The transformer you have bought is not a replacement for the one that blew, and will NOT work.

You need to contact the manufacturer and see if you can get the specs and winging diagram and pin outs of the old transformer. Then you can buy a replacement and solder the the connections to the conductor side of the board.

I think though you need professional help, or at least a good CO2 fire extinguisher handy.

 

[Bucknekked]

I sell smoke in the offing.

Your pictures have vaporized by the way, like that circuit board will when you are finished with it.

I did see the pictures before they vaporized.

The transformer you are trying to use is clearly in no way similar to the one you removed. The transformer you have bought is not a replacement for the one that blew, and will NOT work.

You need to contact the manufacturer and see if you can get the specs and winging diagram and pin outs of the old transformer. Then you can buy a replacement and solder the the connections to the conductor side of the board.

I think though you need professional help, or at least a good CO2 fire extinguisher handy.

I love TLS Guy posts on topics like this. The only reason I kept reading this thread was to see what TLS Guy would say. I had a bet with myself on how it would look. I win. I'm going out now to spend my winnings.

 

[Johnny2Bad]

No , its difficult to get these type of transformer .The ones that get soldered directly onboard :/ .
Yes , the old transformer had multiple taps on the outputs .

I find that hard to believe (that it's difficult to find a direct replacement). Download the Hammond catalog and have a look. They have multiple varieties of PCB-mount transformers. Others would have similar options available from stock.

Every country on earth has transformer manufacturers, because they are often heavy; even if your manufacturing cost is higher than elsewhere, you can sell at relatively high prices and once shipping is figured in, it ends up less expensive in the local market.

Even a country as small as Canada (33 million people) has more than 20. It's a relatively low tech industry (or at least it can be) and the barriers to entry are low.

Plus, if it really came to it, every transformer manufacturer will make you one to your specs.

Having said all of that, my main concern is your inexperience. You can kill yourself playing with transformers, you know.

 

[TLS Guy]

I find that hard to believe (that it's difficult to find a direct replacement). Download the Hammond catalog and have a look. They have multiple varieties of PCB-mount transformers. Others would have similar options available from stock.

Every country on earth has transformer manufacturers, because they are often heavy; even if your manufacturing cost is higher than elsewhere, you can sell at relatively high prices and once shipping is figured in, it ends up less expensive in the local market.

Even a country as small as Canada (33 million people) has more than 20. It's a relatively low tech industry (or at least it can be) and the barriers to entry are low.

Plus, if it really came to it, every transformer manufacturer will make you one to your specs.

Having said all of that, my main concern is your inexperience. You can kill yourself playing with transformers, you know.

The trouble is we do not know the spec. There are multiple pin outs on his old transformer. So we do not know how his was configured. In other words we do not know the voltage of all the taps, and if there are any center taps.

This job is not always easy. Here are pictures of a transformer replacement I did on a friend's preamp, that fried the transformer.

Old transformer photographed with replacement.

View of new transformer in place. There were 12 and 5 volt taps and center tap.

 

[Johnny2Bad]

The trouble is we do not know the spec. There are multiple pin outs on his old transformer. So we do not know how his was configured. In other words we do not know the voltage of all the taps, and if there are any center taps.

This job is not always easy.

And the reason we do not know these things is the OP's inexperience. I hesitate to offer pointers to determine the values, since I am not confident he would survive the attempt.

 

[slipperybidness]

So, have you ever wanted to open that $300K piece, just to see how it was made? Not even little? Maybe just once? What could it hurt? C'mon! It'll be like driving into Wisconsin!

Nope!

I'm too busy with real work, and I know that eventually the opportunity comes to open up every single piece of equipment to see what broke and if I can get the parts to repair it.

I completely tore apart a $25k instrument yesterday, the $10k board that I needed inspect was at the very bottom of the chassis. Found corrosion on the sockets, sent it to our internal electronics repair techs. I could do the repairs, but it's not my job and more importantly I don't have the tools to do it at work (only have those tools at home). For $10k replacement, it's worth a shot to repair in-house first.

And, this instrument also had one of our micro-controllers in it.