transformer and transistor question

[rtill]

If a transistor is wired in wrong, can it hurt the transformer?
I suspect I have a transistor wired in wrong in my power amp I have built... the 300 watt mosfet http://www.circuits-lab.com/?p=81
My transformer gets extremely hot and starts to make a fizzle sound and there is no audio. I have my transformer and power supply setup as a test unit for all power amps I build, so I know that the power supply is correctly wired.

 

[Nico Ras]

Make sure that you have the mosfets placed correctly. Can you give your layout and I will browse through it to see if I can spot any mistakes.

Regards

Nico

 

[Nico Ras]

HERE IS THE FULL PROJECT PACKAGE including gerber plots and PDF files.

http://digisec.co.za/ras/music/RAS 240 mosamp Rev02

The PCB has been revised and made smaller. Remember that the power devices ar under the PCB facing up. In other words, the PCB clamps the power devices to the heat sink.

Kind regards

Nico

 

[Nico Ras]

Sorry, forgot the file extension

http://digisec.co.za/ras/music/RAS 240 mosamp Rev02.zip

 

[nigelwright7557]

If a transistor is wired in wrong, can it hurt the transformer?

If it becomes short it could overheat the transformer in a short period.

This is why I put fuses in the cct before the rectifier to catch any problems. 2 fuseholders is cheaper than a new transformer !

 

[AndrewT]

that's why I have to keep repeating that one should use a bulb tester for the start up of EVERY project and for the modification of EVERY project.

 

[Nico Ras]

that's why I have to keep repeating that one should use a bulb tester for the start up of EVERY project and for the modification of EVERY project.

I AGREE WITH YOU.

I HAVE OFTEN LOST OUTPUT DEVICES THIS WAY.

AFTER I BUILD IT I AM ALWAYS SURE THAT IT IS CORRECT.

I AM PROVEN WRONG MORE OFTEN THAN I WOULD LIKE TO ADMIT.

 

[rtill]

Make sure that you have the mosfets placed correctly. Can you give your layout and I will browse through it to see if I can spot any mistakes.

Regards

Nico

Hi Nico...well, my layouts tend to follow the schematic exactly. ....part placement is exactly the same as the schematic. It just makes it easier for me to troubleshoot I guess. I did find my 2sj162 was wired wrong...I mistook the drain for the source and vice versa, I must not have looked at the schematic close enough. However, after correcting that, I plug in my amp and my transformer fizzles. I am assuming I probably ruined it from wiring the mosfet incorrectly. Am I correct in assuming that? Thanks for everyones help!

 

[Nico Ras]

Hi Nico...well, my layouts tend to follow the schematic exactly. ....part placement is exactly the same as the schematic. It just makes it easier for me to troubleshoot I guess. I did find my 2sj162 was wired wrong...I mistook the drain for the source and vice versa, I must not have looked at the schematic close enough. However, after correcting that, I plug in my amp and my transformer fizzles. I am assuming I probably ruined it from wiring the mosfet incorrectly. Am I correct in assuming that? Thanks for everyones help!

I guess you have fried them.

 

[nigelwright7557]

Hi Nico...well, my layouts tend to follow the schematic exactly. ....part placement is exactly the same as the schematic. It just makes it easier for me to troubleshoot I guess. I did find my 2sj162 was wired wrong...I mistook the drain for the source and vice versa, I must not have looked at the schematic close enough. However, after correcting that, I plug in my amp and my transformer fizzles. I am assuming I probably ruined it from wiring the mosfet incorrectly. Am I correct in assuming that? Thanks for everyones help!

Have you put fuses after the transformer ?
If not it could be a transistor(s) is shorted and putting a huge load on the transformer and making it buzz.

 

[AndrewT]

plug in a bulb tester and start measuring what is going on!!!!

 

[Nico Ras]

Here is the pin out. It is different to HEXFET

 

[rtill]

so looking at that.... this is correct....

 

[rtill]

Here is the pin out. It is different to HEXFET

that is for the 2sk1058....isn't it? (diode points toward drain)
the 2sj162 would have the diode pointing to the source...right?

 

[Nico Ras]

that is for the 2sk1058....isn't it? (diode points toward drain)
the 2sj162 would have the diode pointing to the source...right?

Yes that is correct. Sorry I should have pasted both. this is 2SJ162

Nico

 

[rtill]

ok...tested my transistors with a bulb tester, all test fine.
Put in a new transformer (30-0-30 3 amp Hammond))
Put in inline 3 amp fuses and they immediately blow when turning it on. What will cause this?

 

[Lumba Ogir]

Andrew,

that's why I have to keep repeating that one should use a bulb tester for the start up of EVERY project and for the modification of EVERY project.

Maybe you`re gonna get the Big Bulb Award for that effort someday.

 

[AndrewT]

ok...tested my transistors with a bulb tester, all test fine.
Put in a new transformer (30-0-30 3 amp Hammond))
Put in inline 3 amp fuses and they immediately blow when turning it on. What will cause this?

Andrew,

Maybe you`re gonna get the Big Bulb Award for that effort someday.

How does one blow a 3A fuse when using the bulb tester?

 

[Nico Ras]

How does one blow a 3A fuse when using the bulb tester?

Could be 55W 12V car light bulbs.

rtll,

rather post your PCB layout or send it to me, it sounds as if you got something wrong.

This amp is very simple, and that could be the reason for making a mistake.

You may overlook your mistake because you have the net-list in your head and what you see is not necessarily what you think you see.

 

[Nico Ras]

I am curious, how did you test the transistors. Were the light on only when you biased the gate?