Cambridge Azur 640V2 - protection light one burst

[plopdaweurld]

Hi there,


My amp refuse to output anything, just after selecting the right output (click sound) the protection light shows up (one time flash).
At first, it was just sometimes, i just power off & on and it was ok...but now it's everytime.

I tried to replace the relays (four), as it's a common fix for this amp but no luck, still the same..

If anyone has a clue...

thanks !

 

[tomchr]

I'd check the various conditions the protection circuit is supposed to detect, for example DC on the output. Measure each one. Once you know why the protection circuit trips, you'll know what to fix.

Alternatively, I'd look for an electrolytic cap in the protection circuit that's gone cranky over time.

Try to get a schematic for the amp. It may be as simple as asking Cambridge for one.

Tom

 

[nigelwright7557]

The output DC shouldn't be more than a couple of 100 millivolts.
If its miles off then the amp is likely faulty.
If it isn't maybe the DC offset pot might need adjusting.
Or the protection circuit has a fault.

 

[dazcwl]

If the 640 is anything like the 540a you may want to check the voltage regulators. I replaced all 3 (15v, -15v and 5v) after having similar issues.

 

[Toronto]

I been having issues with my 540a clipping the protection mode.I narrow it down to the board where I heard the click that sets off the protection mode.This may sound crazy but I shut down the amp,and flip it over and the protection mode goes off.Off course every time I shut off the amp or put into standby I have to do the same thing again to shut off protection mode so I just leave the amp on all the time.There has to be a regulator or faulty cap that is causing this.

 

[tomchr]

Or a bad connection somewhere. Are the regulators mounted on PCB-mount heat sinks? Have they rattled loose?

Tom