Re: TEk 475 removing replacing big electrolythics


Scott Singelyn
 

Denis,

I have tried the "hobby saw" type with some success, and I have tried a
jeweler's saw as well. It all factors around the space available to
work with, vs things you don't want to cut off. The stiffer backed
blades stayed on-track better, but did not have any flex in them to
allow to saw at a bit of an angle. The jeweler's saw did offer the best
"purchase" for cutting through the tabs, but requires the other end to
be hooked into the bow/holder, something that may not present itself as
an option depending on the physical space you have to work with.
I am not in a position where I can justify multi-jillion dollar
desoldering/re-work/reflow stations to accomplish these tasks. I'm sure
that these purpose-built devices may work better, however, I do not do
enough of these to justify the cost.

Thank you for your comments!
-- Scott --

On 11/24/2014 12:23 PM, Denis xyzzx_adv@... [TekScopes] wrote:

Scott, Think you have done a great job describing a method of
removing large can electrolytics with minimal chance of damaging the
board. Have you considered using a "hobby saw" blade (thinner blade
with a stiffener edge (a minature miter saw)? DenisK
From: "Scott Singelyn scotts@... [TekScopes]"
<TekScopes@...>
To: TekScopes@...
Sent: Monday, November 24, 2014 9:11 AM
Subject: Re: [TekScopes] TEk 475 removing replacing big electrolythics

Hi Alan,

Now I am sure others on this site may chastise me for my methods, but
here is how I remove these big cans from the 7000 series boards. There
was enough stand-off between the cap base and the board to get this to
work. If there is enough gap to work with for the 475 PS caps, this may
work for you.

I was never able to apply enough of, or the right amount of heat to
unsolder these big caps. I felt that I was beginning to scorch the
board (it sure smelled so), so I backed off that idea and went a little
radical. I used a single ended hacksaw blade holder (like the following
link), to saw off the cap's pins and tabs just above the PCB. I was
very careful to not nick the PCB, and simply sawed through all of the
tabs and pins. After the caps were hacked out, it was a simple matter
to unsolder the tab and pin bits, as the giant heat-sink cap bodies were
no longer there. I was able to use a 25w pencil iron. It took me a
while to saw through everything, as I went very slow, being very
careful. I even slipped a piece of heavy card-stock paper between the
blade and the PCB to help reduce the risk of damaging the board traces.
I used the finest toothed blade I could find. You will need to clean up
any fillings to make sure that no shorts occur later.

http://images.asia.ru/img/alibaba/photo/51652754/Sawfish_Mini_Hacksaw.jpg

I also have used just the blade with the end/grip part wrapped with tape
to protect my hand.

I suggest you weigh in all your options, and pick whatever method works
best for you.

Now await the storm of posts recommending against this, but is does work
if you are very careful.

--

===============================
Scott Singelyn
N8ZPJ@...
===============================

On 11/24/2014 11:39 AM, alan_w_global@... [TekScopes] wrote:

Hi Everyone,


I need some guidance. I have removed two large caps which were
damaged, but in the process of removing them I may have caused more
damage, I can't find any clear pcb layout masks in any of the pdf
manuals, do they exist? there are only very unclear photo's with
components. Does anyone know where I can find a layout of the reverse
side of the main board, is it two sided? by taking out two capacitors
i've damaged the tracks and fear that there is a link on the reverse
side I have severed.


I could do with some simple instructions of how to remove caps, is it
worth buying a hard copy of a manual which one?






Alan




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