Replacing Can Capacitors 400 series scopes


Craig Cramb
 

Wondering if anyone would care to pass along tips for removal of the larger can capacitors in equipment such as the 400 series power supply section. There are large quantities of solder and seems to take a lot of heat and easy to damage the traces thru pins between the upper and lower sections. I currently have good desolder equipment but still seem to have an issue getting all the solder out of the holes to disconnect from upper and lower traces without overheating them.


Paul Amaranth
 

Take the can apart from the top side leaving the pins in the board, then you can more easily desolder them.

It's a pain no matter which way you do it.

Maybe add some chipquick to lower the melting point.

Stock up on PCB repair materials :-)

Paul

On Sat, Dec 05, 2020 at 10:04:06AM -0800, Craig Cramb wrote:
Wondering if anyone would care to pass along tips for removal of the larger can capacitors in equipment such as the 400 series power supply section. There are large quantities of solder and seems to take a lot of heat and easy to damage the traces thru pins between the upper and lower sections. I currently have good desolder equipment but still seem to have an issue getting all the solder out of the holes to disconnect from upper and lower traces without overheating them.







!DSPAM:5fcbcba7219208873113387!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Tad
 

I've replaced hundreds of PS filter caps over the years using high quality
de-soldering equipment.
To ensure that ALL the solder on both sides of the main board is molten, I
used a Weller 100/140 gun along with the de-solder tip.
After sucking up all the molten solder, the dead cap always dropped out on
the bench, leaving nice, clean holes for the new cap.
A little practice goes a long way....


Craig Cramb
 

To ensure that ALL the solder on both sides of the main board is molten, I
used a Weller 100/140 gun along with the de-solder tip.

Maybe add some chipquick to lower the melting point.
Stock up on PCB repair materials :-)

Thanks guys for you assistance. I’ve worked at these over the years and never been happy with the results. Sometimes it is a total disaster, but usually yes very difficult. I have also done the desolder wand and then an additional solder wand at the same time but it just seems trying to get it warm enough can cause the barrel between the traces to get too hot and separate from board traces and possibly come out with the capacitor tab. Maybe I’m running my irons too hot. Which then is repair parts time. I’ve never tried to locate these repair parts as now sure what that barrel piece is really called.


Chuck Harris <cfharris@...>
 

You want lots of power, and a low temperature, no more
than 600F, which is about 315C.

With the right shaped tip, you can work at 500F, which
is about 260C.

That means high wattage temperature regulated irons.

Heat coupling is important, so the first step should
be overfilling the joint with 63/37 solder.

I heat up the joint with a 70W iron, and my PACE desoldering
iron. When I can melt the filling solder, I fill the
joint with solder, and wait a bit, for the whole joint
to liquify. Then I vacuum out all of the solder.

The recycler in me has a feeling that Chipquick will be
banned one of these days.

-Chuck Harris

Craig Cramb wrote:

To ensure that ALL the solder on both sides of the main board is molten, I
used a Weller 100/140 gun along with the de-solder tip.

Maybe add some chipquick to lower the melting point.
Stock up on PCB repair materials :-)

Thanks guys for you assistance. I’ve worked at these over the years and never been happy with the results. Sometimes it is a total disaster, but usually yes very difficult. I have also done the desolder wand and then an additional solder wand at the same time but it just seems trying to get it warm enough can cause the barrel between the traces to get too hot and separate from board traces and possibly come out with the capacitor tab. Maybe I’m running my irons too hot. Which then is repair parts time. I’ve never tried to locate these repair parts as now sure what that barrel piece is really called.






Thomas Garson
 

Another technique is to use ChipQuick, which is a very low melting point solder.

Heat the joint up to solder melt point and quickly suck/wick out as much regular solder as you can without having heat linger too long. While the joint is still solder melt hot, add ChipQuick, having been dipped in paste flux, to the residual preexisting solder. The different alloys will mix and create an amalgam that stays molten at a much lower temperature and also is weaker mechanically, facilitating far gentler part removal.

I often use ChipQuick to assist in the nondestructive (to the PCB) removal of multi pin through hole parts from plated through hole multi layer boards. ChipQuick is especially effective in assisting removal of old parts from PCBs with embedded power and ground layers that can be a bugger as those layers wick heat away much quicker than "active" layers.

While the somewhat expensive flux that ChipQuick sells is very good, I haven't found it to be any more effective than using any good quality electronics flux in the process.

ChipQuick is not cheap, but what cost is a damaged irreplaceable PCB?

Thomas Garson
Aural Technology, Ashland, OR
By my calculation, the dynamic range of the universe is roughly 679dB,
which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps.

On 12/5/20 11:25 AM, Tad wrote:
I've replaced hundreds of PS filter caps over the years using high quality
de-soldering equipment.
To ensure that ALL the solder on both sides of the main board is molten, I
used a Weller 100/140 gun along with the de-solder tip.
After sucking up all the molten solder, the dead cap always dropped out on
the bench, leaving nice, clean holes for the new cap.
A little practice goes a long way....


Craig Cramb
 

Another technique is to use ChipQuick, which is a very low melting point solder.

Thanks I was unfamiliar with ChipQuik, Got some ordered from GoKimco. Sounds like this should help solve the issue.

Craig


Roy Thistle
 

On Sat, Dec 5, 2020 at 04:25 PM, Craig Cramb wrote:


I was unfamiliar with ChipQuik
There are many kinds of solders.... a lot of them are alloys based on tin.
ChipQuik is just tin alloyed with Indium: Sn/In... about half and half... for ChipQuik Indium Solder Wire
Solders with Indium in them were recently discussed in another thread on TekScopes.
Indium is certainly not as toxic as lead... but, don't grind the solder and inhale the dust.