Re: Desoldering Fitting for Soldering Iron

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"Computer Nerd Kev"

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** If the IC is faulty  - what you do is cut the pins off near the package  
and remove each pin from the PCB separately with tweezers and a fine, hot  
tip.

Clean up with a solder sucker or wick.

Then you can install a 40 pin socket or two, 20pin strips to the holes.



...   Phil







Re: Desoldering Fitting for Soldering Iron

"Computer Nerd Kev"
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** I have managed to get them out undamaged with simple, hand operated  
solder sucker and wick.

Takes about 15 - 20 minutes.

Cutting the leads is quicker.

That contraption you linked is bizarre.


....   Phil  



Re: Desoldering Fitting for Soldering Iron

"Computer Nerd Kev"
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** IME there is no hazard to the chip inside a 40 pin DIL pak  -  you only  
heat one pin at a time, so the chip does not even get warm. The main worry I  
had was in pulling out plated through vias with the pins and damaging fine  
tracks on the PCB.

In a one case, after installing a socket, I retried the same 40 pin IC and  
the device ( a CRT monitor) worked perfectly.

In another, installing a new IC made the original fault worse than with the  
old one fitted - this was in a Yamaha R1000 digital reverb unit from the  
mid/late 1980s.

Warming the 40pin IC directly produced the fault - a huge noise in the  
sound.

Turned out, there was a design problem in all early production units.

The eventual fix was to replace 6 memory interface ICs with higher speed  
versions.



...  Phil












Re: Desoldering Fitting for Soldering Iron
On 29/03/2014 3:22 PM, Phil Allison wrote:
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Wrong.


you only

Extended heating of one pin can certainly damage a chip. That's why it a  
very good idea to get your tecnique down pat on scrap boards before you  
attempt to desolder a chip you want to keep.



Re: Desoldering Fitting for Soldering Iron
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<snip>

USD$10 including postage from China;
http://www.aliexpress.com/item/s/1343912318.html

--  
Bob Milutinovic
Cognicom


Re: Desoldering Fitting for Soldering Iron
On 29/03/2014 7:14 PM, Bob Milutinovic wrote:
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Not for the first time, I'm left wondering how they can possibly make a  
profit on that.

Even if the gear itself fell off the back of a lorry.

Sylvia.

Re: Desoldering Fitting for Soldering Iron
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Indeed. You couldn't even buy the requisite raw materials (to make it  
yourself) in Australia for less than double that price.

But look at the number of sub-$1 (including postage) items on eBay, selling  
by the tens of thousands. Even if, as you say, they fell off the back of a  
truck, I still wouldn't put myself through the hassle of listing,  
monitoring, responding, packing and posting in order to make less than $1  
per transaction - but there're obviously people who're happy to do it.

--  
Bob Milutinovic
Cognicom


Re: Desoldering Fitting for Soldering Iron
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Depends how many you were making - look up the prices for plastic resin
on Alibaba. You could get recycled stuff from within Australia too.

The real trick is the design, assembly etc. And in Aus, you'd have to meet
safty requirements and anwser for those loose 240VAC wires.

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Well, think of this scenario: You buy a thousand for $50 (factory rejects sold
by workers, ghost runs etc.). Pay a couple of blokes $5/day each to pack and
post 50 each day (slap on printed stickers and tape up the envelope). Then
with $0.50 profit an item, you could grab $0.5x50 = $25 a day - $10 pay = $15
1000/50 = 20days of work, $15x20= $300 - $50 purchase price = $250 profit.

$250/20 = $12.5 a day earned by you, which would go a lot further
in an economy where you can get by on $5. Of course there would be extra
expenses, but I'm sure your average Chinese Ebay man would have a lot more
than one item on the go.

What I don't understand so well is how some smaller sellers sell items for
$6.00, but only move one or two a week (looking at the num. sold figures on
Ebay). I guess they could be stall holders who are just on the 'net for some
extra dough.

NOTE: I've never been to China and I don't really know the average wage for
working class Chinese. I'm just imagining a scenario based on the single figure
of item price and to me it seems possible.

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Re: Desoldering Fitting for Soldering Iron
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Or moving upmarket, if you want to avoid getting cramps in your thumb (from  
repeatedly re-arming the sucker)...

USD$97 including postage;
http://www.aliexpress.com/item/s/716919381.html

USD$167 including Fedex courier delivery;
http://www.aliexpress.com/item/s/1428629757.html

--  
Bob Milutinovic
Cognicom


Re: Desoldering Fitting for Soldering Iron
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But that's the same model as the Ebay one I linked to.

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More avoid getting electrocuted by the barrel or having the plastic melt at
my fingertips. I'd be replacing the manual solder sucker with a vacuume pump
anyway, as in the web page that gave me the idea.

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Cheaper to get a replacement iron for a desoldering station like the one I
linked to, then just use my existing vacuume pump and power supply.

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Thanks, but if I wanted to spend that sort of cash, I'd probably already have
bought the desoldering station from Rockby (if they have stock).

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Re: Desoldering Fitting for Soldering Iron
On 30/03/2014 7:07 AM, Computer Nerd Kev wrote:
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I put off buying a desoldering station for a long time and regret it  
now. Such a useful tool, and desoldering a 40 pin IC cleanly in a about  
a minute and easily...

Not only that, I've got a few jobs desoldering and socketing chips for  
others to repair vintage equipment so it's paid for itself.

Out of curiousity, what are the two 40 pin chips you are/were trying to  
salvage?

Re: Desoldering Fitting for Soldering Iron
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The chips are PPI-8255 Parallel Interface ICs, a product of the early PC era.

I want to grab one off a control board I was given from an old Dot-Matrix
printer so that I can build an IC tester as described here:
http://dsaprojects.orgfree.com/electronics/ic_tester/ic_tester.html

I looked inside the highest wattage hair straightener I got to see if the
temperature range could be extended. Unfortunately there's no info online
about the chip used (likely some cheap clone because the "ST" logo is
actually printed upside down). I'd probably end up just building a
self-destruct funtion into the hair straightener anyway.

The best option is probably buying that spare desoldering gun at rockby
and using my existing vacuum pump and transformer.

I haven't really started the project yet anyway because I want to work out
a good method for making the PCB (I don't want to lay out that whole circuit
on Veroboard like most other things I do). Last time I tried, with a small
single layer board, I used almost all of a $45 transparancy film pack trying
to get a passable result and ended up with traces like Swiss Cheese and
some having to be cut with a Dremmel.

The printer I was using jams with photo paper (and a lot of normal paper
for that matter), but I've actually got a few laser printers around so one
day I'll have to try the full fleet. I read that the backing from sticker
paper works, which could be good because I know where I could get some cheap,
but I don't know how I'll go feeding it through a printer.

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Re: Desoldering Fitting for Soldering Iron
On 19/07/2014 7:22 AM, Computer Nerd Kev wrote:
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  snip
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Quite an effort.
They are $6 delivered on ebay.

Tony


Re: Desoldering Fitting for Soldering Iron
On 19 Jul 2014, Tony wrote:

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Look at the list of supported ICs, I looked into those first  
and they're hopeless.

I've looked at a few projects out there and this one seems to  
have the best set of tested ICs (excluding designs relying on  
even harder to find parts) and the ability to program in new  
ones. Plus it tells you what part of a chip test failed.

If something like this (or newer):
http://www.andysarcade.net/personal/tech/ABIICIT/index.htm
popped up cheap, I'd definitely be after it instead.

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Re: Desoldering Fitting for Soldering Iron
On 19/07/2014 7:22 AM, Computer Nerd Kev wrote:
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I received an old Casio fax board today with 5 M5L8255AP-5's on it. I'm  
happy to desolder one and send it your way if you don't want to tackle  
the desoldering yourself.

Alternatively the other poster mentioned new ones available for about $6  
posted on Ebay, which is a pretty good option too.

Re: Desoldering Fitting for Soldering Iron
On 21 Jul 2014, Clocky wrote:

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Thanks, that would be great. I can pay for postage by PayPal if  
you want - should be able to send it as a "Large Letter" for  
$1.40.

You can send me a message at:
spamable
-you know what symbol I mean-
safe-mail.net

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Re: Desoldering Fitting for Soldering Iron
On 28/07/2014 7:59 AM, Computer Nerd Kev wrote:
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Did you get my email?


Re: Desoldering Fitting for Soldering Iron
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Did you not get my reply?
Sent it on the 30th according to my "Sent" folder.

I'll try sending again.

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Re: Desoldering Fitting for Soldering Iron
On Sat, 29 Mar 2014 19:14:08 +1100, "Bob Milutinovic"

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I have one of those.  Sort of works but to remove a 40-pin DIP from a
PTH board you're going to be at it forever.

Remember that the button to release the sucker is way up the handle,
so you wind up using a "dagger grip" (or two hands on the tool if
you're a Tasmanian with a  spare).  It is a most awkward way which is
a PITA on high pin counts.

If the O/P isn't trying to salvage the chip, (s)he should just cut the
legs and remove them one by one.  The amount of residual in the holes
on the 40-pinner is going to make dislodgement after the first round
of sucks far from easy.

BTDT

Re: Desoldering Fitting for Soldering Iron
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Problem is that heat guns are relatively expensive too. But today I
discovered another option along the same lines:
http://hackaday.com/2014/03/30/reflowing-with-a-hair-straightener/

I posted a comment about my idea that such hair straighteners could be used
to desolder ICs. I'll have a look in some Op-Shops for old ones at the end of
the week.

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