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Bad solder effects - The first step in every home repair...

 
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krytron



Joined: 05 Sep 2009
Posts: 28
Location: Europe

PostPosted: Sun Oct 11, 2009 10:31 pm    Post subject: Bad solder effects - The first step in every home repair... Reply with quote

This applies to all models and types of CE.

What I'm not sure about is the type of problems bad solder can cause.
I can imagine it increases resistance and lowers the current thus causing the current to be below its normal value.
On the other hand, it increases the voltage drop so if some regulator takes reference value from it, the output would increase above normal value.
All in all, bad solder would either cause lower-to-normal or above-to-normal values for a particular signal, but never both.

Right, wrong, or undecidable?


Thanks.


Last edited by krytron on Thu Oct 15, 2009 11:40 pm; edited 1 time in total
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krytron



Joined: 05 Sep 2009
Posts: 28
Location: Europe

PostPosted: Wed Oct 14, 2009 5:11 pm    Post subject: Reply with quote

I thought it's one of the most rudimentary things to know when doing repairs. Confused
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krytron



Joined: 05 Sep 2009
Posts: 28
Location: Europe

PostPosted: Thu Oct 15, 2009 11:41 pm    Post subject: Reply with quote

Nobody, even a word or two Question Question Question
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Fri Oct 16, 2009 3:07 am    Post subject: Reply with quote

Bad solder joint (same as cold solder) is the same as a broken/intermittent connection between two points. If there is high current involved, it will cause it to heat up and creates a voltage drop.
Depending on the severity of the junction, it will begin to attenuate and act like a resistance in the path of a signal.
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krytron



Joined: 05 Sep 2009
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Location: Europe

PostPosted: Sat Oct 17, 2009 3:20 pm    Post subject: Reply with quote

If you read my first post, that's exactly what I wrote about bad/cold solder (except for excess heating).
Cold solder causes intermittent changes in voltage or current. It increases resistance, so it generates additional voltage drop - everything clear so far.

When bad/cold colder "kicks in", generally one of the following happens:

  1. some electrical value drops below its nominal value
  2. some electrical value jumps above its nominal value
In my monitor problem, "some electrical value" is the red signal voltage, which both drops below and jumps above nominal value. So the question is can bad solder produce the third type of the problem:

-> 3. some electrical value randomly and intermittently drops below and jumps above the nominal value

Question Question Question
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krytron



Joined: 05 Sep 2009
Posts: 28
Location: Europe

PostPosted: Sat Oct 17, 2009 5:07 pm    Post subject: Reply with quote

Can't edit own posts, so have to make another...

Spell error in the above post: colder = solder, of course.

Wanted to add that above-and-below nominal value jumps of the red signal level make me crazy, as I can't distinguish between bad solder and potentially bad IC... plz help. Confused
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sat Oct 17, 2009 10:44 pm    Post subject: Reply with quote

Perhaps instead of keep repeating yourself, if you spend a little time to read about basic ohms law or how an RGB circuit suppose to work, you may have a better understanding.

ONE MORE TIME;
For a signal to get from point A to B, it must have a solid connection in order for the electrons to flow. If and when there is a break (ie cold solder) between A and B, there will be a break in signal path, meaning that it can ONLY cause a decrease in value no matter what type of signal is passing through.

Rather than pondering about a cold solder joint's behavior, If you have a fluctuating red signal, the correct way is to look at the print and follow the signal from the source to destination. You may have to use a meter or a scope to spot check the signal along it's path. There may be bad connection anywhere in the signal path or even a problem in the drive circuit that generates the control signal. Depending on the unit, it may be difficult or awkward to access certain points but that is how is done.
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Oct 18, 2009 5:32 pm    Post subject: Re: Back to Basics... Reply with quote

krytron wrote:
vtech wrote:
Perhaps instead of keep repeating yourself, if you spend a little time to read about basic ohms law or how an RGB circuit suppose to work, you may have a better understanding.

Having BSEE and MSCE degrees, and working at the university should be assurance enough that my understanding of the Ohm's Law is quite sufficient. Rolling Eyes


Woooops Should of known....No offense but enough said.
No need to go any further. Shocked
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Oct 25, 2009 8:38 pm    Post subject: Re: Back to Basics... Reply with quote

krytron wrote:
vtech wrote:
Woooops Should of known....No offense but enough said.
No need to go any further. Shocked

For whatever this means. Confused
No offense... but thought this is a serious technical forum.


Obviously you don't have a clue
You are asking to be banned.
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