[pinkfloyd4ever]

ok, so I FINALLY got around to hooking up panel components to my cmoy. I hooked up the power switch (I'm using the one on the RK097) and the battery clip and then when I tested I hear a buzzing when the source is off. Once I turn the source on though, it goes away. Is this normal? I guess as long as it only happens when the source is off, it doesn't really matter does it? I'm just concerned b/c it wasn't happening when I tested it before(meaning after soldering all the components to the board). I changed the R3s from 1.02k(gain 11) to 3.3k(gain 4). Oh and I also changed the LED resistor from a Xicon 10k 1% to a ratshack 4.7k 5%, and I replaced my ratshack 4.7k 5% R1s with V-D RN55 4.64k (couldn't get 4.7k). Crap, I probably shouldn't have changed that many things w/o testing it.

EDIT: oh ya, I forgot to mention, when i move pick up the amp & battery or just move them around, the buzzing gets softer or louder (usually softer)

 

[TzeYang]

check pot grounds.

Something's wrong with your ground loop.

 

[pinkfloyd4ever]

I haven't even hooked up the actual pot yet, just the power switch in it

 

[TzeYang]

is there a input ground resistor?

and really, consider rechecking your ground loop. and take a few pics.

 

[pinkfloyd4ever]

input ground resistor? I'm using tangent's tutorial, is that R2?
I'm workin on those pix

edit: pix

 

[achina]

Some of those solder joints on those socket pins don't look too good. Hard to tell from the pictures but it looks like they could do with a reheating.

 

[pinkfloyd4ever]

Quote:

Originally Posted by achina /img/forum/go_quote.gif Some of those solder joints on those socket pins don't look too good. Hard to tell from the pictures but it looks like they could do with a reheating.

hmmm, some of the resistor-socket connections (not the solder joints but the leads inside the socket) are pretty loose, but when I pull on them they do catch before they come out. would that cause buzzing only when the source is off tho?

 

[mminutel]

Fix any loose connections. Check for solder bridges. Also, just a thought: "plug in the headphones you are using into a different source and wiggle it around and make sure that isn't the culprit. I spent a few hours on my new CMOY finding out why it was buzzing to find out that my phones had a short with the ground. However, mind was buzzing while it was on.

All connections should be tight. Cold solder joints might work but they will fail eventually. What gain are you using on the Pimeta? What phones do you have to use with it?

-EDIT- I cannot exactly tell by your picture, but is there a solder bridge on the number 4 pin of your OPAmp to VGround? Nothing on the opamp should be grounded directly.

Clean it off with some high purity alcohol to clean the flux. That can hide bridges and is just not a good thing in general.

 

[Ace o' Spades]

Quote:

Originally Posted by mminutel /img/forum/go_quote.gif Also, just a thought: "plug in the headphones you are using into a different source and wiggle it around and make sure that isn't the culprit.

Yeah, absolutely make sure that you test with more than one set of earphones if you can so that you can be sure that the amp is indeed the culprit. I spent half an hour today troubleshooting a cmoy before realizing the ******* KSC75 volume control was lowered.

Also, why do you have 2 different brands of capacitors on there? Seems a bit silly.

EDIT: almost forgot. The circuit might be picking up interference from your computer monitor, fluorescent lights, etc. When I was putting together that CMOY today the thing buzzed like hell until I cased it up, probably due to the lights right above the workbench.

 

[pinkfloyd4ever]

Quote:

Originally Posted by mminutel /img/forum/go_quote.gif I cannot exactly tell by your picture, but is there a solder bridge on the number 4 pin of your OPAmp to VGround? Nothing on the opamp should be grounded directly. Clean it off with some high purity alcohol to clean the flux. That can hide bridges and is just not a good thing in general.

Ya I was thinking the same thing about that possible bridge, I fixed it after I took the pix but before I posted em, and I've still got the buzzing.

I have the gain at 4 right now

will the 93% alcohol work for cleaning flux? If not, where do I get it in higher purity?
How do you do that, you have to scrub it right, not just pour it on and blow it off with the canned air? Obviously paper towels wouldn't work too well.

Quote:

Originally Posted by Ace o' Spades /img/forum/go_quote.gif Also, why do you have 2 different brands of capacitors on there? Seems a bit silly.

I was supposed to be using a rail splitter, so I only ordered 1 power cap. However I fried the rail splitter tring to solder it. Damn suppliers were all out of the 3-pin version. So I bought the other cap from a local place that sells components.

Quote:

Originally Posted by Ace o' Spades /img/forum/go_quote.gif almost forgot. The circuit might be picking up interference from your computer monitor, fluorescent lights, etc. When I was putting together that CMOY today the thing buzzed like hell until I cased it up, probably due to the lights right above the workbench.

I was kinda thinking that too, but it wasn't happenning before and I tested it in the same place both times. ARRR I'll have to do all this stuff after this weekend (reheating solder, cleaning flux, etc), I'm goin to visit some friends at my old school in Indiana. I'll let you guys know what happens when I do get around to it.

 

[mono]

Try putting it in a metal case to shield it.

I think the solder joints may be ok electrically but to be sure you mind add some flux (since there is enough solder) and reflow them. Just heating may not do so well on the unplated Ratshack board.

As for alcohol, some people are picky and want it as pure as possible but yes you can use 93%, even 70% and scrub it with a toothbrush/etc. Rinse it a couple times and gently shake or hang it to dry, you don't need to wipe off the solvent but avoid getting it in the POT. IF the alcohol mix you use produces a hazy film after drying, it is not functionally problematic but if you consider it unsightly then you would use a purer or different alcohol formulation to rinse (but it could just be that you hadn't gotten all flux off and another scrub and rinse with same would work).