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Voltage high on U1 between pin 3 and pins 4 & 5

PostPosted: Sun Jul 17, 2011 3:53 pm
by Montrealaise
I finished assembling my second A12 and I'm get +-25V between pin 3 and pins 4&5 on U1. I can't see any problems with the component installation.
I've checked all the caps mentioned that could be potentially installed backwards, looked for shorts etc. but I am not finding any issues. I did a visual check between another A12 that I finished and that is working well and I can't see any differences.

Initially when I first powered up, I blew a cap at c15 that I must have wired backwards. Since replacing it, I re-powered and am now having the issue described. Could it be that I damaged some other components on my first power up?

Problem solved… partially

PostPosted: Sun Jul 17, 2011 5:38 pm
by Montrealaise
It turned out that there were some cold solder joints. Once I fixed them, I was able to get the voltages exactly right… But when I put in the brand new SC25, I got wrong voltage between U1 pin 4 and pin 6. It turns out that the Op Amp is probably to blame. U5 runs extremely hot with the new -never used Op Amp, but when I swapped out the new SC25 and replaced it with the tried and tested SC25 everything is swell and the voltage can be adjusted to perfection.

I tried the suspect SC25 in the older (previously functioning A12) and the U5 on that card immediately started to overheat. Can I send this malfunctioning SC25 back I wonder?

PostPosted: Mon Jul 18, 2011 8:28 am
by tpryan
Send an e-mail to rma@seventhcircleaudio.com for return instructions.