Seventh Circle Audio

[the3030club]

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!

[jmoliner]

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.

[tpryan]

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.

[jmoliner]

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.

[jmoliner]

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...

[tpryan]

Good job!