OldSynths

Hi:
Can someone advise the best way to desolder chips from a circuit board?
I am working on my CS-60 and want to replace 40xx chips with new, but
dont want to do more damage than good.
I will be putting in sockets in their place to make repair easier in
the future.

Is there a good method or desolder tool that heats the whole chip at
once?
The only other way I know is to clip off the leads, remove the chip,
and then desolder the remaining pieces of lead from the board.

Please advise (Crow??)

Regards
Rory McDonald
OLDSYNTHS MODERATOR

Many swear by solder wicks...but I've never gotten the technique. A heat
gun with proper tip is usually the best I think. Solder suckers (the $6.00
type with a pump and trigger) are ok often though on double sided can be
quite a challenge at times. Heat gun in those cases I believe is the only
good way not to damage board. -Bob

----- Original Message -----
From: <rorymcd@...>
To: <oldsynths@yahoogroups.com>
Sent: Sunday, September 12, 2004 10:51 PM
Subject: [oldsynths] Best way to desolder chips?


> Hi:
> Can someone advise the best way to desolder chips from a circuit board?
> I am working on my CS-60 and want to replace 40xx chips with new, but
> dont want to do more damage than good.
> I will be putting in sockets in their place to make repair easier in
> the future.
>
> Is there a good method or desolder tool that heats the whole chip at
> once?
> The only other way I know is to clip off the leads, remove the chip,
> and then desolder the remaining pieces of lead from the board.
>
> Please advise (Crow??)
>
> Regards
> Rory McDonald
> OLDSYNTHS MODERATOR
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>

>> Can someone advise the best way to desolder chips from a circuit board?
>> I am working on my CS-60 and want to replace 40xx chips with new, but
>> dont want to do more damage than good.
>> I will be putting in sockets in their place to make repair easier in
>> the future.
>>
>> Is there a good method or desolder tool that heats the whole chip at
>> once?

An expensive desoldering station probably works like a charm. I've never
had the pleasure of using one.

>> The only other way I know is to clip off the leads, remove the chip,
>> and then desolder the remaining pieces of lead from the board.

This is the slowest but safest way, especially if you're not worried about
saving the chip.

>Many swear by solder wicks...but I've never gotten the technique. A heat
>gun with proper tip is usually the best I think. Solder suckers (the $6.00
>type with a pump and trigger) are ok often though on double sided can be
>quite a challenge at times. Heat gun in those cases I believe is the only
>good way not to damage board. -Bob

Since this is a vintage piece of gear I'd forget the solder wick (it might
be useful for cleanup if used sparingly). I only keep some around for those
occasions when nothing else works and I know the board can take the heat.
I've heard people who know what they're talking about praise the heat gun
approach but I've never tried it myself. In the past (mid-eighties) I
repaired a lot of commercial equipment that had been in the field a long
time and we NEVER used solder wick because the danger to the board was too
great and a quality, properly-maintained solder sucker worked far better
and faster (we used Soldapults that cost $20-30 apiece back then). Today a
desoldering station would probably be the commercial approach to this.
Interestingly the tech students from the local community college had never
SEEN a solder sucker--that was the beginning of their real education in
circuit board work.

We also defluxed the boards with copious amounts of CFC's. Those were the
days...

--

Terry Bowman, KA4HJH
"The Mac Doctor"

The best (and most expensive) way is to get something like the Den-On
SC7000Z:

http://www.howardelectronics.com/den-on/sc7000.html

I bought one several years ago and it is by far the best tool I've ever
bought for circuit board repair. I've used it many times to swap out the
40xx chips in CS-80s. Once you use one there is no going back.

I would suggest #80-4-5 solder wick made by Chemtronics as the cheap way
to go. Some solder wicks are terrible, mostly due to wrong mesh size.
The one I indicated is a good size for desoldering chip leads. I think
Digikey still sells the Chemtronics line.

Crow
/**/

On Sun, 12 Sep 2004, rorymcd@... wrote:

> Hi: Can someone advise the best way to desolder chips from a circuit
> board? I am working on my CS-60 and want to replace 40xx chips with new,
> but dont want to do more damage than good. I will be putting in sockets
> in their place to make repair easier in the future.
>
> Is there a good method or desolder tool that heats the whole chip at
> once? The only other way I know is to clip off the leads, remove the
> chip, and then desolder the remaining pieces of lead from the board.
>
> Please advise (Crow??)
>
> Regards
> Rory McDonald
> OLDSYNTHS MODERATOR

  The best (and most expensive) way is to get something like the Den-On
SC7000Z:

http://www.howardelectronics.com/den-on/sc7000.html

  I bought one several years ago and it is by far the best tool I've ever
bought for circuit board repair.  I've used it many times to swap out the
40xx chips in CS-80s.  Once you use one there is no going back.

  I would suggest #80-4-5 solder wick made by Chemtronics as the cheap way
to go.  Some solder wicks are terrible, mostly due to wrong mesh size. 
The one I indicated is a good size for desoldering chip leads.  I think
Digikey still sells the Chemtronics line.

Crow
/**/

On Sun, 12 Sep 2004, rorymcd@... wrote:

> Hi: Can someone advise the best way to desolder chips from a circuit
> board? I am working on my CS-60 and want to replace 40xx chips with new,
> but dont want to do more damage than good. I will be putting in sockets
> in their place to make repair easier in the future.
>
> Is there a good method or desolder tool that heats the whole chip at
> once? The only other way I know is to clip off the leads, remove the
> chip, and then desolder the remaining pieces of lead from the board.
>
> Please advise (Crow??)
>
> Regards
> Rory McDonald
> OLDSYNTHS MODERATOR

Crow,

I bought one of these years ago at a flea market in silicon valley.
The man had two, one with a tip, and the other without. Thinking the
tips would be an easy lathe project, I chose the one which kept more
money in my pocket...

And have regretted it ever since<G>

What size tip(s) would you recommend for "normal" through hole work?

Ballendo

P.S. Any tips gained through use you'd like to share? Do you use
yours for SMD work too?

--- In oldsynths@yahoogroups.com, The Old Crow <oldcrow@o...> wrote:
>
> The best (and most expensive) way is to get something like the
Den-On
> SC7000Z:
>
> http://www.howardelectronics.com/den-on/sc7000.html
>
> I bought one several years ago and it is by far the best tool
I've ever
> bought for circuit board repair. I've used it many times to swap
out the
> 40xx chips in CS-80s. Once you use one there is no going back.
>
> I would suggest #80-4-5 solder wick made by Chemtronics as the
cheap way
> to go. Some solder wicks are terrible, mostly due to wrong mesh
size.
> The one I indicated is a good size for desoldering chip leads. I
think
> Digikey still sells the Chemtronics line.
>
> Crow
> /**/
>
> On Sun, 12 Sep 2004, rorymcd@m... wrote:
>
> > Hi: Can someone advise the best way to desolder chips from a
circuit
> > board? I am working on my CS-60 and want to replace 40xx chips
with new,
> > but dont want to do more damage than good. I will be putting in
sockets
> > in their place to make repair easier in the future.
> >
> > Is there a good method or desolder tool that heats the whole chip
at
> > once? The only other way I know is to clip off the leads, remove
the
> > chip, and then desolder the remaining pieces of lead from the
board.
> >
> > Please advise (Crow??)
> >
> > Regards
> > Rory McDonald
> > OLDSYNTHS MODERATOR

I like the 1.5mm (that is the hole size) tip for general desoldering. I
use the 'thin' 1mm tip for SMD rework, along with the hot air blowgun kit.

If you treat the tips well (keep them clean and unclogged!) they'll last
a long time. I'm still using the original 1mm standard tip on my older
desoldering gun.

My tips for using this tool: do not make the temperature any hotter
than absolutely necessary. I keep mine under 500C, usually around 450C.
Also, do not use paste flux to clean the tip or suction tube; the liquid
flux will be pulled into the filter wadding, gumming it up. Try not to
leave the gun on for long periods of time; this will wear out the tip/tube
faster..I clogged up a tip when I left the thing on over a weekend. Keep
the tip clean constantly, and tinned. The effectiveness of the tool
declines reapidly if the tip face is not wet with solder. When using it,
try to hold the tool level or with the tip pointed slightly upward--try to
avoid pointing the tip downward as this will increase the chance of
evacuated solder flecks falling back into the suction tube and clogging
it. There is a cleaning rod in the handle of the tool, use it whenever
the airflow sounds impaired--just make sure to cool the cleaning rod with
a damp paper towel or sponge before storing it in the handle again. For
more severe clogs, use the set of larger gauge cleaning rods that came
with the gun.

Next, some joints or pads may require *adding* a bit of solder to the
jucntion before the desoldering tool will effectively remove all the
solder. The idea is to get as much heat transfer through the joint so
that all the solder melts, then trigger the suction. Run it for about 2
seconds at a time, and pull the tip away from the board while the trigger
is still down to let air push the solder out of the tube and into the
collection cartridge. I sort of do 3 seconds to heat junction, 2 seconds
of suction and about 1/2 second of suction sustained after the tip is
pulled away from the board.

Oh, and 1-sided boards such as in the CS-50/60/80 are easy.
Plated-though boards are less easy to desolder, but with a clean tool tip
and the above notes, it is not difficult.

Clean the cartridge out after every session (not every single junction,
just at the end of a desoldering session. Make sure the small air slots
at the bottom of the cartridge aren't plugged with solder--you may have to
pull out the filter wadding to chisel out such solder.

Hope this helps,

Crow
/**/

On Sat, 9 Oct 2004, ballendo wrote:

> Crow,
>
> I bought one of these years ago at a flea market in silicon valley.
> The man had two, one with a tip, and the other without. Thinking the
> tips would be an easy lathe project, I chose the one which kept more
> money in my pocket...
>
> And have regretted it ever since<G>
>
> What size tip(s) would you recommend for "normal" through hole work?
>
> Ballendo
>
> P.S. Any tips gained through use you'd like to share? Do you use
> yours for SMD work too?

Excellent reply. Thank you!

Ballendo

--- In oldsynths@yahoogroups.com, The Old Crow <oldcrow@o...> wrote:
>
> I like the 1.5mm (that is the hole size) tip for general
desoldering. I
> use the 'thin' 1mm tip for SMD rework, along with the hot air
blowgun kit.
>
> If you treat the tips well (keep them clean and unclogged!)
they'll last
> a long time. I'm still using the original 1mm standard tip on my
older
> desoldering gun.
>
> My tips for using this tool: do not make the temperature any
hotter
> than absolutely necessary. I keep mine under 500C, usually around
450C.
> Also, do not use paste flux to clean the tip or suction tube; the
liquid
> flux will be pulled into the filter wadding, gumming it up. Try
not to
> leave the gun on for long periods of time; this will wear out the
tip/tube
> faster..I clogged up a tip when I left the thing on over a
weekend. Keep
> the tip clean constantly, and tinned. The effectiveness of the
tool
> declines reapidly if the tip face is not wet with solder. When
using it,
> try to hold the tool level or with the tip pointed slightly upward--
try to
> avoid pointing the tip downward as this will increase the chance of
> evacuated solder flecks falling back into the suction tube and
clogging
> it. There is a cleaning rod in the handle of the tool, use it
whenever
> the airflow sounds impaired--just make sure to cool the cleaning
rod with
> a damp paper towel or sponge before storing it in the handle
again. For
> more severe clogs, use the set of larger gauge cleaning rods that
came
> with the gun.
>
> Next, some joints or pads may require *adding* a bit of solder to
the
> jucntion before the desoldering tool will effectively remove all
the
> solder. The idea is to get as much heat transfer through the joint
so
> that all the solder melts, then trigger the suction. Run it for
about 2
> seconds at a time, and pull the tip away from the board while the
trigger
> is still down to let air push the solder out of the tube and into
the
> collection cartridge. I sort of do 3 seconds to heat junction, 2
seconds
> of suction and about 1/2 second of suction sustained after the tip
is
> pulled away from the board.
>
> Oh, and 1-sided boards such as in the CS-50/60/80 are easy.
> Plated-though boards are less easy to desolder, but with a clean
tool tip
> and the above notes, it is not difficult.
>
> Clean the cartridge out after every session (not every single
junction,
> just at the end of a desoldering session. Make sure the small air
slots
> at the bottom of the cartridge aren't plugged with solder--you may
have to
> pull out the filter wadding to chisel out such solder.
>
> Hope this helps,
>
> Crow
> /**/
>
> On Sat, 9 Oct 2004, ballendo wrote:
>
> > Crow,
> >
> > I bought one of these years ago at a flea market in silicon
valley.
> > The man had two, one with a tip, and the other without. Thinking
the
> > tips would be an easy lathe project, I chose the one which kept
more
> > money in my pocket...
> >
> > And have regretted it ever since<G>
> >
> > What size tip(s) would you recommend for "normal" through hole
work?
> >
> > Ballendo
> >
> > P.S. Any tips gained through use you'd like to share? Do you use
> > yours for SMD work too?