Blew my transformer

rs1026 · 14th August 2004, 06:23 PM

Hi folks,
I was trying to build a amp based on stk 4192 II chip. Since 4192 accepts 8ohm loads.I connected two 4ohm full range speakers in series just to test the amp.

As soon as I turned the power the transformer went to smokes!!
But I could hear some music for 20sec or so. It sounded horrible. It was more noise than music.!

I used a 20-0-20,5amps rating transformer. I think it could not deliver sufficeint current hence got burnt out.

Any ideas what could be the reason and possible solutions.
Somehow I am not very sure of stk 4192's capability. Data sheet looks fine but I havent met anyone who tried using 4192.

Any suggestions??

Thanks,

djQUAN · 14th August 2004, 07:02 PM

probably oscillation or motorboating.

janneman · 14th August 2004, 07:56 PM

Quote:

Originally posted by rs1026
Hi folks,
I was trying to build a amp based on stk 4192 II chip. Since 4192 accepts 8ohm loads.I connected two 4ohm full range speakers in series just to test the amp.

As soon as I turned the power the transformer went to smokes!!
But I could hear some music for 20sec or so. It sounded horrible. It was more noise than music.!

I used a 20-0-20,5amps rating transformer. I think it could not deliver sufficeint current hence got burnt out.

Any ideas what could be the reason and possible solutions.
Somehow I am not very sure of stk 4192's capability. Data sheet looks fine but I havent met anyone who tried using 4192.

Any suggestions??

Thanks,

It is almost impossible to blow a transformer by overloading an amp. It really, really is extremely unlikely. Most probably there was either a problem with the transformer wiring or the rectifier (or the amp), in such a way that there was a dead short across the secondaries.

I would suggest to take out the transformer and see if it really is blown. 20 secs or so is not enough to blow a transformer, which can only be blown by thermal overload (and high-voltage overload, but that will not be the case here). And transformers have BIG thermal capacity. Take the naked transformer, separate out the wires to be sure there are no shorts, and apply mains (to the right terminals!) and measure the AC secondary voltage. Chances are it is OK. Then of course the real fun starts....

Jan Didden

sss · 14th August 2004, 07:59 PM

probably the bridge diodes are blown

Franz G · 15th August 2004, 07:29 PM

Could you show us your psu schematics please and how you connected the trafo?

Franz

karma · 15th August 2004, 10:06 PM

Quote:

Originally posted by sss
probably the bridge diodes are blown

i second that

carlosfm · 16th August 2004, 12:03 AM

If you messed up the PSU connections to the chip, that is, you invert + with -, you may kill the trafo in seconds.

That's why you should always use a fuse in the primary, with the correct value.
The fuse would blow before the trafo.

janneman · 16th August 2004, 06:49 AM

Quote:

Originally posted by carlosfm
If you messed up the PSU connections to the chip, that is, you invert + with -, you may kill the trafo in seconds.
That's why you should always use a fuse in the primary, with the correct value.
The fuse would blow before the trafo.

Beg to differ Carlos, you CANNOT blow a transformer in seconds. No way. Even a dead short on the secondaries (which as about as bad as it can get) will not do that. It takes time.

Jan Didden

PMA · 16th August 2004, 06:59 AM

How about rated primary voltage of the transformer, does it fit to your local distribution network voltage?

Jean · 16th August 2004, 08:32 AM

Quote:

Originally posted by janneman

Beg to differ Carlos, you CANNOT blow a transformer in seconds. No way. Even a dead short on the secondaries (which as about as bad as it can get) will not do that. It takes time.

Jan Didden

What he said

14th August 2004, 06:23 PM	#1
rs1026 diyAudio Member Join Date: Jul 2004 Location: Bangalore	Blew my transformer Hi folks, I was trying to build a amp based on stk 4192 II chip. Since 4192 accepts 8ohm loads.I connected two 4ohm full range speakers in series just to test the amp. As soon as I turned the power the transformer went to smokes!! But I could hear some music for 20sec or so. It sounded horrible. It was more noise than music.! I used a 20-0-20,5amps rating transformer. I think it could not deliver sufficeint current hence got burnt out. Any ideas what could be the reason and possible solutions. Somehow I am not very sure of stk 4192's capability. Data sheet looks fine but I havent met anyone who tried using 4192. Any suggestions?? Thanks,

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14th August 2004, 07:02 PM	#2
djQUAN diyAudio Member Join Date: May 2004 Location: manila	probably oscillation or motorboating.

14th August 2004, 07:59 PM	#4
sss diyAudio Member Join Date: Jul 2003 Location: Israel , haifa	probably the bridge diodes are blown

15th August 2004, 07:29 PM	#5
Franz G diyAudio Member Join Date: Jun 2004 Location: Bern / Switzerland	Could you show us your psu schematics please and how you connected the trafo? Franz

16th August 2004, 12:03 AM	#7
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	If you messed up the PSU connections to the chip, that is, you invert + with -, you may kill the trafo in seconds. That's why you should always use a fuse in the primary, with the correct value. The fuse would blow before the trafo.

16th August 2004, 06:59 AM	#9
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	How about rated primary voltage of the transformer, does it fit to your local distribution network voltage?

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