Ticking Transformer

Garnett · 11th April 2006, 10:56 AM

Hi there - I have been building a simple LM3875 based kit using an old EI transformer. The transformer has varios output points including three I am using for 24-0-24 output. When I wired it up to the rectifier board I got a decent 33.7 v output and everything seemed perfect.

However, I've added the two channels to the mix and soldered on the input sockets and now when I plug it in and switch on the transformer makes a ticking noise.

Can anyone tell me what this is? Is this the "hum" lots of other people have mentioned? Why didn't the transformer make this noise before?

Thanks for any tips.

lndm · 11th April 2006, 12:46 PM

Is this ticking noise more of what you would call a buzz?

Garnett · 11th April 2006, 01:01 PM

Quote:

Originally posted by lndm
Is this ticking noise more of what you would call a buzz?

Each "tick" is detectable and it's approx 120 bpm...

Moving the various bits and pieces around doesn't affect the sound.

lndm · 11th April 2006, 01:10 PM

Hmmm, odd. Could it be the xfmr rapidly heating and expanding?

Whether so or not, it may be best to sweep your circuit with your dmm. A long shot, sweep the circuit with a cro?

BrianDonegan · 11th April 2006, 01:25 PM

I had a transformer make the same noises. It was melting (too much current draw). Is it getting hot to the touch?

Garnett · 11th April 2006, 01:33 PM

Quote:

Originally posted by BrianDonegan
I had a transformer make the same noises. It was melting (too much current draw). Is it getting hot to the touch?

Eeerrk!
Not that I've noticed (I did try to see, but didn't want to leave it plugged in too long - no detectable heat for the 10 seconds or so I leave it on for).

As I said, it didn't make this sound before I wired up the actually amplifiers and the inputs. Is it worth me doing some tests with the ol multimeter?

Quote:

Originally posted by lndm
Whether so or not, it may be best to sweep your circuit with your dmm. A long shot, sweep the circuit with a cro?

Sorry - I'm fairly new - what sort of thing should I be checking? (and what do you mean by cro?).

Thanks for helping me out.

lndm · 11th April 2006, 02:14 PM

Um. I mean an Oscilloscope (cathode ray oscilloscope). I figured you would first check that the circuit is performing as expected with your dmm. The oscilloscope could help track down an oscillation which may cause a large current draw. These can be hard to detect in other ways.

Dave Cigna · 11th April 2006, 08:18 PM

I'm guessing that the transformer is saturating during the short current pulses to charge the caps. It's possible that your amp is oscillating and drawing a lot of current even without an input signal and the transformer is just not up to the task. How big is it?

Dave Cigna · 11th April 2006, 11:39 PM

Quote:

Originally posted by Garnett
Each "tick" is detectable and it's approx 120 bpm...

The first time I read this as 120 bps (i.e. 120Hz.) I wondered how you could discerned 120 ticks per second... But, you really said something like 2 ticks per second. So can I change my guess?

Ok, I don't have a real good guess. Might be picking up something external like a cell phone....

Fossil · 12th April 2006, 05:52 AM

if u r using those 25A or 35A rectifier in a square can, that could be the problem. There seems to be alot of faulty ones everywhere in the market. I had them too...I remember the transformer giving out a buzz...think it was saturating!

11th April 2006, 10:56 AM	#1
Garnett diyAudio Member Join Date: Feb 2006 Location: London	Ticking Transformer Hi there - I have been building a simple LM3875 based kit using an old EI transformer. The transformer has varios output points including three I am using for 24-0-24 output. When I wired it up to the rectifier board I got a decent 33.7 v output and everything seemed perfect. However, I've added the two channels to the mix and soldered on the input sockets and now when I plug it in and switch on the transformer makes a ticking noise. Can anyone tell me what this is? Is this the "hum" lots of other people have mentioned? Why didn't the transformer make this noise before? Thanks for any tips. __________________ Usually mitigation for all my dumb questions: I will endeavour to make sure I explain everything I find out on www.substitutereality.co.uk so that other newbies like me have a useful resource to check first...

11th April 2006, 01:25 PM	#5
BrianDonegan diyAudio Member Join Date: Dec 2004 Location: Rock Ridge	I had a transformer make the same noises. It was melting (too much current draw). Is it getting hot to the touch? __________________ Twisted Pear Audio

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11th April 2006, 12:46 PM	#2
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Is this ticking noise more of what you would call a buzz?

11th April 2006, 01:10 PM	#4
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Hmmm, odd. Could it be the xfmr rapidly heating and expanding? Whether so or not, it may be best to sweep your circuit with your dmm. A long shot, sweep the circuit with a cro?

11th April 2006, 02:14 PM	#7
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Um. I mean an Oscilloscope (cathode ray oscilloscope). I figured you would first check that the circuit is performing as expected with your dmm. The oscilloscope could help track down an oscillation which may cause a large current draw. These can be hard to detect in other ways.

11th April 2006, 08:18 PM	#8
Dave Cigna diyAudio Member Join Date: Oct 2003 Location: Finger Lakes, NY	I'm guessing that the transformer is saturating during the short current pulses to charge the caps. It's possible that your amp is oscillating and drawing a lot of current even without an input signal and the transformer is just not up to the task. How big is it?

12th April 2006, 05:52 AM	#10
Fossil diyAudio Member Join Date: Sep 2001 Location: SG	if u r using those 25A or 35A rectifier in a square can, that could be the problem. There seems to be alot of faulty ones everywhere in the market. I had them too...I remember the transformer giving out a buzz...think it was saturating!