Having a problem with Carver M-200t transformer thump

[Cavscout 8]

I just acquired a Carver power amplifier. Was unable to test it up on purchasing. But I got a good deal on it (I think) so I took the chance.
It does work (plays music) but it cuts out.
With nothing plugged into except power I found that the transformer is "thumping".
Other than the transformer being bad, is there something else fixable that can cause this ?
If a new transformer is needed, can anyone recommend a source ?
Thank you

[wrf 4,395]

Welcome to the site.  Sorry to hear about your amplifier having problems.

 

Most carver amplifiers that "cut out" are going into protection for some reason.  Very unlikely that the transformer has anything to do with the problem.  In fact, the M-200 is what carver calls a Mag Coil power supply.  It is NOT a standard transformer.

 

Your amp needs a complete checkup to determine IF and WHY is is going into protection.  Check the manuals here on the site.  There is an excellent service manual for the M-200.  It contains a great theory of operation section and a detailed check out procedure.  

 

Good Luck.  Let us know how it goes.  One you narrow down the problems we may be able to assist you.

[Rob 4,833]

Welcome to the site.

 

Is the amp making the thumping sound when you are turning it off or is it making this sound while it is powered on? Can you be more specific? 

Is the amp powering off or is the protection light coming on when it cuts out? 

 

CHECK TURN-OFF thumps.

(lv rms output into 8 ohms)

A) Left channel ±2V peak.

B) Right channel ±2V peak.

 

Edited February 22, 2024 by Rob

[Cavscout 8]

It in not when turning on or off.

It is active constantly and with nothing connected.

See video here:

 

https://youtu.be/0FRgXrBHqSg?si=b88anbzDhK9ctWpV

[Rob 4,833]

Did you measure the rail's and Bias voltages? And on top of that you dont know the history of it. It could have sat for years and caps went bad. That doesn't sound to me like a bad transformer.

 

 

Edited February 22, 2024 by Rob

[Cavscout 8]

1 hour ago, Rob said:

Did you measure the rail's and Bias voltages? And on top of that you dont know the history of it. It could have sat for years and caps went bad. That doesn't sound to me like a bad transformer.

 

 

I haven't tested anything yet.

I will have to get a manual.

But the transformer is upstream of the capacitors and I can confirm to you that the thump IS coming from the transformer. 

[Rob 4,833]

ok

Edited February 22, 2024 by Rob

[Rob 4,833]

Yeh, Things can make the transformer create different noises. 

 

https://thecarversite.com/manuals/mandir/Carver M-200t Service Manual.pdf

 

Here's your manual

[3M_Audio 1,555]

These transformers aren't fed a continuous sine wave, so if the circuitry that controls the AC line to the transformer has a problem, you can end up with all kinds of strange artifacts and issues. Same goes for output from the transformer to the gain stages - it's not conventional.

 

As @Rob and a few others have pointed out, peruse the service manual and in particular the troubleshooting and theory of operation sections and that should get you pointed in the right direction. And if the repairs are outside your comfort zone, there are some good resources you'll be able to find here on TCS.

[BobTFM35 2,316]

I found, that when I downloaded the service manual that it was missing the pages numbered "5" and "6".

 

 

[BobTFM35 2,316]

@wrf @Sk1Bum I emailed a complete copy of the service manual to Wayne. It has the two missing pages.

[wrf 4,395]

Updated manual has been posted.

 

@Cavscout -- Is the protect LED coming on at all?

[Cavscout 8]

Not at all.

 

[BobTFM35 2,316]

It does not look like when the noise happens that the amp losses power. Is that true?

Maybe the next question is related or not related to the problem but I was curious.

Can I assume that the Thermal switch is either mounted inside the ends of the transformer or somewhere very close?

 

When I listen to that sound it brings back moments of similarities to the noises that I would experience when pressing the start button for a motor on a piece of lab equipment and the contacts were made.