K2 Noise Solved

[DDWEBB]

A few weeks back I wrote that I was experiencing  a most unusual noise
problem. I had hoped that someone else might have had  the same problem and would
have the answer. This didn't happen.
The  noise was noticeable when the volume control and RF Gain were at minimum
and  even the antenna disconnected.  
I want to thank Gary,   KI4GGX, who was of great encouragement to me is the
solving of this problem. He  even suggested I record the noise.  I did and sent
it to him to hear.
I  finally decided to use the bruit force approach and used a 1000 UF
capacitor  with one side grounded.
Starting at U9 the audio amp, shorting leads to  ground through the
capacitor, I discovered the noise was coming in via the  CW side tone path. I traced
the noise to the input to U 10B pin 5.
Under a  high intensity light and a magnifying glass, all solder pads looked
clean and  shiny.
Not knowing where else to go, I resoldered all the pins of U10 plus  C36. I
suspect C36 may have been my problem but all that noise has now gone  away.
Don Webb...KA7L  




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[Don Wilhelm-4]

Don,

I have a strong suspicion that the solder pad did not receive enough
heat initially.  It can happen that the solder looks nice and shiny, but
the solder does not have good flow onto the pad.  I have seen that
condition more times than I would like.  It is the result of too low a
soldering temperature.

A word to potential builders - keep the soldering iron temperature
greater than 700 deg F (750 is better).  You will not damage anything if
the soldering temperature is 800 deg F or below *and* the soldering time
is kept short - contrary to popular belief, damage *will* occur with a
low iron temperature applied for a long period of time.  Also use a
small diameter solder so you can control the amount and watch as the
thru-hole is heated, it will wick a bit of solder into the hole when it
receives adequate heat, but too much applied solder will mask that
process and can hide a bad solder joint.

73,
Don W3FPR

[hidden email] wrote:

> A few weeks back I wrote that I was experiencing  a most unusual noise
> problem. I had hoped that someone else might have had  the same problem and would
> have the answer. This didn't happen.
> The  noise was noticeable when the volume control and RF Gain were at minimum
> and  even the antenna disconnected.  
> I want to thank Gary,   KI4GGX, who was of great encouragement to me is the
> solving of this problem. He  even suggested I record the noise.  I did and sent
> it to him to hear.
> I  finally decided to use the bruit force approach and used a 1000 UF
> capacitor  with one side grounded.
> Starting at U9 the audio amp, shorting leads to  ground through the
> capacitor, I discovered the noise was coming in via the  CW side tone path. I traced
> the noise to the input to U 10B pin 5.
> Under a  high intensity light and a magnifying glass, all solder pads looked
> clean and  shiny.
> Not knowing where else to go, I resoldered all the pins of U10 plus  C36. I
> suspect C36 may have been my problem but all that noise has now gone  away.
> Don Webb...KA7L  
>
>  
>

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[Jack Smith-6]

Don:

I can't find it now, but I remember a column by Robert A. Pease in which
he left a transistor wrapped around  the business end of a soldering
iron at 700F over the weekend as an experiment and found that its
performance specs were still in compliance when he checked it Monday
morning.

A related issue to tip temperature is that a physically small tip will
loose too much heat. There's a happy optimum where the tip possesses
sufficient thermal mass to not cool down when applied to the joint, but
is sufficiently small for the job.

Jack K8ZOA

>
>
> A word to potential builders - keep the soldering iron temperature
> greater than 700 deg F (750 is better).  You will not damage anything
> if the soldering temperature is 800 deg F or below *and* the soldering
> time is kept short - contrary to popular belief, damage *will* occur
> with a low iron temperature applied for a long period of time.  Also
> use a small diameter solder so you can control the amount and watch as
> the thru-hole is heated, it will wick a bit of solder into the hole
> when it receives adequate heat, but too much applied solder will mask
> that process and can hide a bad solder joint.
>
> 73,
> Don W3FPR
>

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