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K3 F Gain mod

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alsopb

K3 F Gain mod

The instructions have you clipping one SMT resistor and then removing
the pieces.

I've did a trial of this method on a junk PCB here.

At least on the board I used, there apparently is some kind of adhesive
under under the chip. The clipping process seems to remove the solder
resist and perhaps any PCB traces under the chip.

Is there anything under R8 that can be damaged?

(Guess not, since nobody complaining. A blow up of the pix doesn't seem
to show anything either)

73 de Brian/K3KO
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David Gilbert

Re: K3 F Gain mod

There are different methods used to solder SMT components to PC boards. The use of adhesive under the body of the component is an older process typically used for wave soldering. Reflow soldering is more common now (especially for single sided boards), where the solder paste is screened onto the board first and then the component leads are placed into the paste. The sticky paste holds the component in place until the solder melts, at which point the surface tension of the solder takes over.

I'm pretty sure the K3 uses the latter technique and wouldn't have any epoxy holding the resistor to the board.

73,
Dave AB7E

------Original Mail------
From: "Brian Alsop" <[hidden email]>
To: <[hidden email]>
Sent: Fri, 29 Jan 2010 21:40:33 +0000
Subject: [Elecraft] K3 F Gain mod

The instructions have you clipping one SMT resistor and then removing
the pieces.

I've did a trial of this method on a junk PCB here.

At least on the board I used, there apparently is some kind of adhesive
under under the chip. The clipping process seems to remove the solder
resist and perhaps any PCB traces under the chip.

Is there anything under R8 that can be damaged?

(Guess not, since nobody complaining. A blow up of the pix doesn't seem
to show anything either)

73 de Brian/K3KO
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Matt Zilmer

Re: K3 F Gain mod

In reply to this post by alsopb

The K3 electronics seems to be assembled with a "clean" SMT process,
which means that only solder paste is used to hold the components on
the board during reflow. The boards are designed for rework.

You should not experience the same problem with K3 PCBA's. I've done
most of the approved rework to the K3 and had no trouble like this.

73,
matt W6NIA
K3 #24

On Fri, 29 Jan 2010 21:40:33 +0000, you wrote:

>The instructions have you clipping one SMT resistor and then removing
>the pieces.
>
>I've did a trial of this method on a junk PCB here.
>
>At least on the board I used, there apparently is some kind of adhesive
>under under the chip. The clipping process seems to remove the solder
>resist and perhaps any PCB traces under the chip.
>
>Is there anything under R8 that can be damaged?
>
>(Guess not, since nobody complaining. A blow up of the pix doesn't seem
>to show anything either)
>
>73 de Brian/K3KO
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

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gm3sek

Re: K3 F Gain mod

Matt Zilmer wrote:

>>The instructions have you clipping one SMT resistor and then removing
>>the pieces.
>>
>>I've did a trial of this method on a junk PCB here.
>>
>>At least on the board I used, there apparently is some kind of adhesive
>>under under the chip. The clipping process seems to remove the solder
>>resist and perhaps any PCB traces under the chip.
>>
>>Is there anything under R8 that can be damaged?
>>
>>(Guess not, since nobody complaining. A blow up of the pix doesn't seem
>>to show anything either)
>>
>>73 de Brian/K3KO

>The K3 electronics seems to be assembled with a "clean" SMT process,
>which means that only solder paste is used to hold the components on
>the board during reflow. The boards are designed for rework.
>
>You should not experience the same problem with K3 PCBA's. I've done
>most of the approved rework to the K3 and had no trouble like this.
>
>73,
>matt W6NIA
>K3 #24

Good information from the man who knows.

But I think it's a bad recommendation for K3 owners to remove SMD
components by crunching them up with diagonal cutters. It's a violent
process - the cutter blades focus a large force into a very small area
- with a significant risk of tearing up the tiny SMD pads and damaging
the board.

Some boards also have hair-fine copper traces routed *between* the pads.
Plow up one of these and you're in real trouble! (Maybe not on the K3 IF
gain mod... but one day you'll regret doing it this way.)

It is much safer - and also much easier - to 'float' the chip gently off
the board by melting the solder on both ends at the same time. As Matt
says, the pads are designed for this kind of rework and the resistor
comes right off.

--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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GW0ETF

Re: K3 F Gain mod

I've just fitted the KXV3A to s/n 145 and did the R8 replacement at the same time.

I used Ian's method....2 fine tipped soldering irons placed each end lifts the chip *immediately*. No adhesive and no worries about damaged board or shards of carbon embedded in your eye...the resistor was also lifted this way off an old PCI board to avoid shipping costs as I'd forgotten to order it with the KXV3A, doh!

73,

Stewart Rolfe, GW0ETF

alsopb

Re: K3 F Gain mod

In reply to this post by gm3sek

Thanks all. I'm the cautious type. Experiment first on something dead.
That's why surgeons practice on cadavers.

73 de Brian/K3KO

Ian White GM3SEK wrote:

>>
>> The K3 electronics seems to be assembled with a "clean" SMT process,
>> which means that only solder paste is used to hold the components on
>> the board during reflow. The boards are designed for rework.
>>
>> You should not experience the same problem with K3 PCBA's. I've done
>> most of the approved rework to the K3 and had no trouble like this.
>>
>> 73,
>> matt W6NIA
>> K3 #24
>
> Good information from the man who knows.
>

Alan Bloom

Re: K3 F Gain mod

In reply to this post by GW0ETF

You don't even need two soldering irons. Just angle the iron almost
flat so the tip touches both ends of the component, then add a big blob
of solder so that you get good thermal contact with both ends at once.
The part will come right off and you can clean off the excess solder on
the pads with solder-removal braid.

Al N1AL

On Sat, 2010-01-30 at 01:22 -0800, GW0ETF wrote:

> I've just fitted the KXV3A to s/n 145 and did the R8 replacement at the same
> time.
>
> I used Ian's method....2 fine tipped soldering irons placed each end lifts
> the chip *immediately*. No adhesive and no worries about damaged board or
> shards of carbon embedded in your eye...the resistor was also lifted this
> way off an old PCI board to avoid shipping costs as I'd forgotten to order
> it with the KXV3A, doh!
>
> 73,
>
> Stewart Rolfe, GW0ETF