Uh oh... sigma 22 mistake
Jun 9, 2009 at 6:32 AM Thread Starter Post #1 of 38


Member of the Trade
Jan 27, 2009
Hey folks,

I powered up my sigma 22's today and the first one worked fine. Second one didn't get any voltage. I realized (too late) that I had CR2 in backwards. Desoldered and resoldered oriented correctly hoping that I didn't fry anything, but alas, still no voltage. Any thoughts about what to check next and what parts may have fried (besides CR2).

So mad... I'm always so careful, checking and double checking. This is my first mistake like this. Oh well... lesson learned.
Jun 9, 2009 at 7:20 PM Post #4 of 38

Originally Posted by oneplustwo /img/forum/go_quote.gif
So mad... I'm always so careful, checking and double checking. This is my first mistake like this. Oh well... lesson learned.

I'll admit that I blew up my s22 the first time, too ;( ;(

I had wired in an electro cap backwards. NEVER EVER did that before. I felt so bad.

...but not as bad as my living room 'felt' with a conic spray of electrolyte deposited on my living room table!!

I call it the 'teapot phenomenon' since the cone of steam from the blown cap reminded me of that

that part mistake took down MANY other parts in b22 boards.


so, its not just you. it happens - and on SUPER powerful things like the sigma, it won't 'stop' if you make a mistake - it will tear you a new one and still keep going ;(

I didn't even bother to tshoot things all that much; I simply replaced almost all active parts at once. my thinking is that I could try replacing a few here and there but the problem would STILL have a chance of taking the NEW parts down. so rather than take the chance, I bulk desoldered all things that seemed like they 'might' need replacing.

resistors and diodes and caps are usually fine (if they look ok) but I assumed (and I was right, a lot) that all transistors had taken a hit or were about to.

this is why I order SETS of replacement parts.
Jun 9, 2009 at 7:26 PM Post #5 of 38
Hmm... not a bad idea. Maybe I'll try a round or two of trouble shooting and then just bite the bullet if I don't make good progress. Any suggestions on a good desoldering station!?
Jun 9, 2009 at 7:35 PM Post #6 of 38
hakko 808. its what saved my butt.

I kept worrying about replacing one part (that might be bad) but then NOT finding the TRUE cause and then having to replace that (again) and others in the chain.

so, rather than take my chances, better and faster FOR ME to just replace ALL mosfets and unsolder each transistor and check it.

on my b22, I had to replace sets of mosfets AT LEAST 2 or 3 times ;( and signal transistors as well.

never blew a crd, I don't think.

blew lots of .47 R's though. I just replace them even if they test ok, now.
Jun 9, 2009 at 8:03 PM Post #7 of 38
I managed to solder in EVERY electrolytic capacitor backwards on my sigma22... I realised just as I soldered the last leg fortunately, so nothing blew up!

No idea how I managed to do that. I've never even got one in the wrong way on anything else I've made!
Jun 9, 2009 at 8:06 PM Post #8 of 38
I did that on my mini-max tube amp. you can pick 'us or euro' style transistors and wouldn't you know, I put the right parts in the wrong hole
all of them. but I did catch this BEFORE power up so no harm done.

I really dislike having 2 'hole choices' in pcb design. too easy for an installer to mess up. I don't like designs like that, to be honest. a good design is builder-proof (lol). I'm serious, too.
Jun 9, 2009 at 8:29 PM Post #9 of 38
did that on my CSS's for my speaker valve amp. 4 very very bright red el84's soon told me something was wrong!
Jun 9, 2009 at 8:39 PM Post #10 of 38
Well, you guys are making me feel a tiny bit better. I guess if you do DIY long enough, it's bound to happen. Hopefully less and less. Too bad there's no magic machine that tells you to just replace part x,y, and z and move on. *sigh* The good news is that one of the sigmas works so I can at least move forward with my beta board tests. You can bet I'll be triple checking those before powering up though!
Jun 9, 2009 at 9:00 PM Post #11 of 38

Originally Posted by oneplustwo /img/forum/go_quote.gif
Well, you guys are making me feel a tiny bit better. I guess if you do DIY long enough, it's bound to happen.

the longer you do it, the more of these little mishaps you have!...the joys of complacency...

as you have a working board, you at least have a reference.
Jun 9, 2009 at 9:32 PM Post #12 of 38

the hakko 808 is the coolest thing ever!!! you will love it. and, btw, i have an "extra" fully built sigma 22 set up for 17v, if you are interested ....... pm me
Aug 17, 2009 at 9:20 PM Post #14 of 38
Old thread, new problem. So the sigma that I have previously tested worked fine. Then I changed to a new shielded trafo from Sumr. Thought I had it wired correctly (still do) but when I powered up, I got a spark and then nothing. Doh! So either something broke because I wired it up wrong or something broke as a coincidence to changing the trafo. Anyway, would everyone please double check my wiring? (This is for US 115V.)

Primary # 1 Black : beginning of winding. White: end of winding.
Primary # 2 Brown : beginning of winding: Orange: end of winding.

Thus Parallel 115V : Black and Brown together, White and Orange together.

Secondary # 1 : Red : beginning of winding, Yellow: end of winding.
Secondary # 2 : Blue: beginning of winding, Grey : end of wnding.

Thus, in the sigma facing the terminal block from right to left, Red, Yellow, Blue, Grey.

If that's not right, what is? And also, if it's not right, what am I most likely to have blown? The spark seemed to come from the Mosfet area but I'm not sure.

Users who are viewing this thread