Seventh Circle Audio

I built my first a12 yesteday and everything went great. My second one was going even more smoothly. but i messed up 2 things, one was a biggie.

I fired up the unit with the C13 capacitor in the wrong polarity. The Led pulsed while it was powered up and the capacitor got hot, but i cut power within maybe 45 seconds before it started smoking or anything like that. am i screwed?

I also lost one of the little ceramic capacitors, so i'm going to try and pick a replacement up. In the meantime there's no way for me to test the unit, i'm afraid it's not going to work!

Hi, I'm new to the forum, so I take this opportunity to greet you: I found lots of information here that has been a great help for me while I was building my kits.

I take this post to say that exactly the same thing happened to me: I installed the capacitor C13 backwards. In step 33, I turned de power on, and some smoke came out of the circuit. At that time, between U1 pin 4 and U1 pin 5 was 0.3 volts, while between U1 pin 4 and U1 pin 3 was 14.3 volts. I reversed the capacitor C13. The same result. I guess that it has a short-circuit.

So I went to buy a replacement, but it seems that is impossible to find in Barcelona (Europe) a condenser with 1500uF/50V.

I tried installing a condenser with 1000uF/63V, but I have not had results: between U1 pin 4 and U1 pin 5 there are still 0.3 volts, and between U1 pin 4 and U1 pin 3 is 14, 3 volts.

Should I buy a condenser with exactly 1500uF/50V, or I may have damaged some other component?

Any response is welcome,

thanks.

You can order replacement parts directly from DigiKey or Mouser using the part numbers on the BOM. Even if it doesn't measure as a direct short, having a reverse voltage applied for even a minute will likely make the part liable to fail in the future. A 1000uF/63V should work as a replacement.

So if a 1000uF/63V electrolitic condenser may work, the problem must come from other components that have been also damaged ...

At the moment I checked the diodes D2-D7, and I found three suspicious readings with my digital multi meter. Try to change them to see if I'm lucky!

I will inform you if I can fix the problem.

Thank you for the response.

I ordered some parts to Digikey as Tpryan suggested to me, and I must say that the services they provide are excellent: the components came in 10 days, perfectly packaged.

Well, in the end I managed to fix the problem. Now, my A12 works perfectly and sounds amazing!

In my case (and I hope that maybe can be of help for someone) I had damaged the capacitor C13 and the voltage regulator U5. Once changed, problem solved!

At last I can enjoy all the kit I bought: J99, N72, A12 and D11. Now I think I have another problem: when I set up a recording session, I can't choose which of the 3! The truth is that all of them sound wonderfully, with a lot of gain and very low noise. PERFECT. I suspect that the A12 will be very well with my voice tone...

Good job!