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Old 23rd June 2012, 12:04 PM   #1
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Question CMoy Ahoy! Help!

First post and first problem!

Have made the foray into DIY by building a CMoy. No sound though. Please help.

PCB purchased from Fred_Fred on eBay.

18V; LED lights up; Have tried swapping op amps and cables; Log Pot used; Can't see any shorts in my soldering (first attempt, so don't laugh too loudly at the attached images - I can hear you).

Thanks for reading and for any feedback you can offer.
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Old 23rd June 2012, 12:30 PM   #2
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Have you got the schematic ? The pictures aren't too clear but I would re-sweat the solder joints as most of them look like "balls" when they should look like "mountains". You could have a few bad joints.
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Old 23rd June 2012, 12:42 PM   #3
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Quote:
Originally Posted by KatieandDad View Post
Have you got the schematic ? The pictures aren't too clear but I would re-sweat the solder joints as most of them look like "balls" when they should look like "mountains". You could have a few bad joints.
A million thanks for your quick response

What do you mean by "re-sweat" the solder joints? Does this?
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Old 23rd June 2012, 01:10 PM   #4
mesc is offline mesc  Norway
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The solder joints are bad. You must re-flow them, preferably adding some flux first. Or remove the solder then reapply, hopefully properly.

Click the image to open in full size.

It should look like that ^. To achieve it, you must heat both the pcb track and component leg at the same time, then apply solder to the heated parts.

Read some guides - Like this: http://tangentsoft.net/elec/movies/

Last edited by mesc; 23rd June 2012 at 01:17 PM. Reason: Removed copyright material
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Old 23rd June 2012, 05:07 PM   #5
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Hi All,

I'm about to start a CMOY amp and I have another question on soldering. From the tangentsoft instructional, it doesn't mention solder bridges aside from one sentence saying that issues with the amp may be caused by solder joints touching one another. But cruising through CMOY images on the web, alot of people have joints bridged all over the place. There's also this instructional that specifies that some soldering bridges should be made in order for the amp to work properly (page 14 of pdf): http://www.calpolyieee.org/projects/cmoyver1.2.pdf. I'd prefer to use the tangentsoft tutorial since it seems to be standard but am I missing something in my intrepretation of it?

Thanks!
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Old 23rd June 2012, 07:45 PM   #6
mesc is offline mesc  Norway
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Soldering bridges: Usually when we talk about soldering bridges, we talk about unintentional contacts between tracks/components/joints etc. Which I imagine is what tangent is talking about.
For someone new at soldering this probably is common.

But when you're building cmoy's on those breadboards, you don't have tracks, so you use lots of solder to make a circuit. Or you can use wires.
Of course you can't make connections all over the place and expect it to work. I mean, what would the use of engineers be if it where so?
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Old 25th June 2012, 10:14 PM   #7
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A solder sucker is an invaluable asset. Get some cheap veroboard, some single core 1.4A cable and practice until you are sure you'll do a good job. Then do the soldering that matters.
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