CTS600 randomly trips fault/thermal protection

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#1 mikaelpap

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Posted 24 March 2014 - 06:16 AM

Unit is connected to 70v speaker lines. Suddenly, fault&thermal leds come on, both chs, no audio output. Power off resets unit to normal operation, only fault to reoccur again. No shorts measured, nor voltage supply abnormalities. Any repair experience or trouble shooting will be appreciated.

#2 joust


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Posted 24 March 2014 - 10:04 AM

You may have encountered what is called the 'crowbar' effect : The CTS600 (as well as the CTS1200) is protected with a crowbar circuit : This circuit, when activated, virtually shorts out the rail voltages through an SCR device. This shunting of the rails voltages is instantaneous and minimal dammage to the amp output circuit. The only way to remove the shunting of the SCR is to remove power to the amp.
I suspect a cap in the LV circuit : C933 (470UF -> change to a 560UF); It has been a little problematic, especially with PIP cards. I'm suspecting the analog side LV supply issue, perhaps a faulty regulator (found under output devices Silpad).