Re: {Collins} soldering technique



Hi Mac:

Is this a DIP package IC or as I originally pictured in that rig, a metal can package.

Everything Paul mentions is proper but cutting the leads and removing one by one and then resoldering from the topside only is probably easier if it is a metal can type.

Generally, it is always preferable to remove the board. I also never desolder anything like a DIP package except by the cut lead one at a time method. Even a good vacuum desoldering tool can damage the pads on older boards--especially non-thru-plated types.

73

Curt

On 2/5/2012 7:35 AM, Paul Christensen wrote:
Mac,

Of course, option 3 is best if you can manage board removal. This would also facilitate the installation of a high quality machined-pin IC socket for the op-amp. Low profile machined-pin IC sockets are not like the common IC socket. These sockets grip the pins and are highly reliable. Although some will argue about the use of sockets in RF and IF applications, they are perfectly acceptable for audio/switching applications and make IC replacement easier if the condition re-occurs.

A fourth option: Cut the leads to the op amp close to the IC. Remove the chip, leaving the cut leads. Then one-by-one, unsolder the pins. Wick the holes and clean the PCB surface. Then insert the new IC and solder. Although unlikely, you may need to trim the leads of the new IC before insertion to avoid contact with the chassis. Unfortunately, this method does not allow you to use a machined-pin IC socket since that requires access to the underside of the PCB.

Paul, W9AC

----- Original Message ----- From: "Mac Koizumi" <je1atw@xxxxxxxxxxx>
To: <collins@xxxxxxxxxxxxx>
Sent: Sunday, February 05, 2012 7:09 AM
Subject: {Collins} soldering technique



Hi friends,

I have a question on soldering technique.

The other day, my KWM-380 suddenly lost audio.
Finally I found the AF output Op-Amp was bad.

So I have to change it but it seems not easy task.

The Op-Amp is mouted on the Receiver-Exiter PCB (double-sided)
and it is not easy to remove PCB from the chassis.

There seems three ways to do it and I wonder which way I should take
and I shouldn't take.
a) Just unsolder the Op-Amp and solder new one without
  removing the PCB.  It seems the leads of the Op-Amp might not
  be soldered well on the back side.
b) Cut the leads of broken Op-Amp halfway and joint the
  leads of new one.
c) Remove the PCB from the chassis and remove old Op-Amp
  completely and solder new one to apply solder on both side
  even it might take long way.

Thank you.

Mac, JE1ATW
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