Help w/ a dead Cmoy...

[n_maher]

Okay, so I jumped into DIY amp building this weekend and whipped up a Tangent modified Cmoy amp. Actually took about 6hrs to just get it wired, I haven't put it in an enclosure as I suspected I might have some problems and figured it'd be easier to troubleshoot it without dealing w/ the tight confines of an enclosure. Turns out I was right!

So here's where I'm at:

Here's what I've tested:
1. Checked power supply, voltage is even and at the anticipated values at both caps.
2. Check power supply to amp - again voltage even and steady at both V- and V+ leg of amp.
3. Checked pin layout of amp to make sure that in,out, V-, V+, and outputs were all in the correct location. (OPA2227PA chip)
4. Tried to check output voltage of amp and this is the only thing that I get that could be weird. On the positive side I measure the output voltage at 0.002 volts which sounds right but on the negative side I get 3.77 volts, and they are positive volts. I don't know enough to know if I'm doing this wrong so I haven't taken this as a sign that my amp is bad, yet.
5. Reread all instructions, troubleshooting, and anything else I could find and I'm stuck...

The amp does nothing. No sound, no hiss, certainly no music when I plug in a source. I'm thinking it has to be something stupid, like I wired an input wrong but I've traced everything and can't find a thing that I think I did wrong.

Here are a few more pics of the various components so maybe somebody can spot something hideously wrong.

The board wired up:

Top of the board:

The Panny Pot:

Pot and Input:

Any help would be greatly appreciated.

 

[gsferrari]

Just curious : On the input socket (miniplug female) I notice you have used the following :-

1 - Gnd
3 - Left
5 - Right

Shouldnt it be :-

1 - Gnd
2 - Left
4 - Right

Also - some of the joints look funky - have you checked for continuity and cross checked by measuring resistance across across the joints?

 

[Earwax]

On the bottom of the board, some of those solder connections of the socket to the board look suspicious, especially the one at the lower left. A few other places look as if there isn't enough solder to make a good connection.

 

[n_maher]

Quote:

Originally Posted by gsferrari Just curious : On the input socket (miniplug female) I notice you have used the following :- 1 - Gnd 3 - Left 5 - Right Shouldnt it be :- 1 - Gnd 2 - Left 4 - Right Also - some of the joints look funky - have you checked for continuity and cross checked by measuring resistance across across the joints?

Hey, that makes two of us. Honestly, I wasn't sure how to wire the input plugs. If you say that it should be a different way, that's news to me and probably good news.

 

[n_maher]

Quote:

Originally Posted by Earwax On the bottom of the board, some of those solder connections of the socket to the board look suspicious, especially the one at the lower left. A few other places look as if there isn't enough solder to make a good connection.

The joints have all been tested for continuity. Are they pretty and perfect, heck no, but should they work, yes. But I'll fire up the gun and give it some more metal if you guys think it might help. I tried to be really careful about not overheating the board and various elements so I erred on the side of less than more.

Right now I'm off to rewire the in and out based on gsferrari's feedback. I'm new to all of this and am bound to have gotten some really simple stuff wrong.

My life's motto: "I only know the answers to all the dumb questions because I already asked them."

Thanks for the help.

Nate

 

[n_maher]

gsferrari,

I owe you a BIG thanks my friend. 10min. w/ the iron and I've now built my first successfully working Cmoy Amp! Wuhoo!

 

[gsferrari]

YAY

Good going pal - enjoy and post more pics once you have it in an enclosure

 

[n_maher]

So, with a little help and some serious time (4hrs) put into laying out and doing the enclosure what I hope to be "the right way" I'm done.

Here it is:

A sincere thanks to both Earwax and gsferrari for taking the time to help out and offer much-needed advice. I did end up resoldering most of the connections on the bottom side while doing the casework, now they not only work they look the part too.

Bring on the Pimeta!

Nate

 

[Earwax]

Excellent job! I find doing the casework to be the hardest part of building an amp.

 

[MisterX]

Nice job for a first amp?




Quote:

Originally Posted by Earwax I find doing the casework to be the hardest part of building an amp.

Funny cause I think doing the casework is the easy part.

 

[n_maher]

It is my first amp and thanks. The casework was hard, but ultimately very rewarding as I'm pleased w/ the relatively clean look of the inside. I'm looking to do a really nice Pimeta amp for the long run but thought that it'd be pretty foolish to start with something that could be a little spendy if I want it to be.

And I'm hugely impressed with the amp and how it makes my Sennheisers sound. I haven't gotten to use it w/ my Etys yet (out on demo loan to a friend) but can only imagine that similar gains will be experienced.

All in all it was a great excuse to buy some tools and a ton of fun for the long holiday weekend although the missus thinks I'm nuts.

 

[gsferrari]

Wow nice job

I SUCK at casework. My first mint case looks like someone pulled out a M-16 and fired two rounds into it

My second case looked nuked

My third case came out decent...

now I am running out of my "Curious George" tins

I was collecting them before wasting three of them so far.

I think I will populate the amp and send you the case + parts for putting everything together

LOL

 

[mustang]

Yeah I'd have to agree that is some nice casework. Much better than mine on my first cmoy anyways...

 

[n_maher]

gsferrari,
not sure i'm ready to go into production just quite yet!

Let's face it, I had a lot of superb examples to look at here for ideas and such. I'm done w/ mint tins though, they're hard to drill and not destroy. I think I'll stick w/ Hammond cases from now on, actually I've got one due in on Wednesday, just not sure what I'm going to do with it. Maybe a MINT is in the works...

I think the DIY sickness has officially begun now

.

N

 

[Heady]

n_maher, I found out the hard way that you don't drill holes in tins, you use a hole puncher to make the holes. It works beautifully.