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<blockquote data-quote="midnightg35x" data-source="post: 6169988" data-attributes="member: 608400">I guess to me that still seems a little less likely to me.&nbsp; How does the ground line get driven high to burn out like that on the 494?&nbsp; If the drive transistors along with the output fets failed, then all the power should be handled along the normal ground plane and the ground wire hooked up to the amp, not through the 494.&nbsp; To go through the 494&#039;s ground pin (like in the picture), the resistance of the +12V to ground internal to the 494 would have to be lower than the resistance of the direct short (due to blown transistors) between +12V and ground on the FET&#039;s.&nbsp; Also, the SMPS transformer isolates the drive transistors from the 494.Now if all transistors blew and the smps transformer saturated (broke) I could maybe believe it would do that because the SMPS fets might draw more current from their gates than the 494 could handle before those SMPS fets blew.&nbsp; I think its much more common for a ground to be loose or a bad connection somewhere compared to the above scenario happening.&nbsp; It is POSSIBLE, but I say start with the more probable option.I agree with your posts about using either a small supply to test it or a supply with a good overcurrent protection.</blockquote>

[QUOTE="midnightg35x, post: 6169988, member: 608400"] I guess to me that still seems a little less likely to me. How does the ground line get driven high to burn out like that on the 494? If the drive transistors along with the output fets failed, then all the power should be handled along the normal ground plane and the ground wire hooked up to the amp, not through the 494. To go through the 494's ground pin (like in the picture), the resistance of the +12V to ground internal to the 494 would have to be lower than the resistance of the direct short (due to blown transistors) between +12V and ground on the FET's. Also, the SMPS transformer isolates the drive transistors from the 494. Now if all transistors blew and the smps transformer saturated (broke) I could maybe believe it would do that because the SMPS fets might draw more current from their gates than the 494 could handle before those SMPS fets blew. I think its much more common for a ground to be loose or a bad connection somewhere compared to the above scenario happening. It is POSSIBLE, but I say start with the more probable option. I agree with your posts about using either a small supply to test it or a supply with a good overcurrent protection. [/QUOTE]

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