One more screwup with the Ace...

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Tue Dec 10 17:02:01 2002

>From: "Philip Pemberton" <philpem_at_dsl.pipex.com>
>
>pete_at_dunnington.u-net.com wrote:
>> On things like that, I often don't even try to rescue any suspect ICs
>> or even passives, just cut them off close to the PCB with a very fine
>> pair of sidecutters, and then desolder the stub of pin.
>That's what I've been doing. I've been desoldering using "Soder-Wick" - I
>got a small reel of it for 90p.
>
>> First thing is to make sure anything you remove is replaced with a
>> good quality socket
>I didn't have any decent sockets - I had to cut two Maplin "economy DIL
>sockets" down to size, fitted two RAMs, then ran out of sockets. In order
to
>limit damage to the ICs due to heat, I gave them a quick blast of freeze
>spray and then soldered them.

Hi
 REAL BAD IDEA! This is just about the worst thing
you can do. Most silicon IC's can take a lot of heat
applied slowly. Thermal shock making a large range
of temperature change is real rough on them and more
likely to fracture the IC or cause the lead seals
to fail.

>
>> and if necessary that you can repair any damaged
>> tracks with stripped wirewrap wire or similar.
>None of the tracks are stuffed, the pads seem to have come up because the
>solder wick stuck to them and pulled them up, even though the wick was
still
>heated.

 This is why I never recommend using solder wick unless you
are vary experienced at desoldering. You need to know the right
size and the right touch of applying the heat with this
material. I do 95% of my desoldering with a sucker and
only the last special cases with wick. I have three different
sizes of wick to select for each job. I use different heat
ranges as well.

>
>> How adept are you
>> with a soldering iron?
>Six years of experience, three with a Maplin elcheapo, three with my Antex
>XS25 (25 watt).

 Rework is not the same as soldering. Rework is a special
talent. When you can remove a 25 pin D PC type D connector
from a 4 layer board with half of the pins connect to large
internal traces, without damaging to board, you can consider
yourself a reworker.
 You absolutely shouldn't be using an non-temperature controlled
iron for rework.
Dwight

>
>> Did you get the 2114s and Z80 I sent you? They should have arrived
>> this morning.
>Yup, they arrived this morning. Fitted them and the random, static garbage
>has been replaced with scrolling garbage. Grr...
>I replaced four out of the five 74LS367s too - no dice. The bloody thing is
>still being stubborn.
>
>As for your offer to have a look at it, I might just take you up on it.
I've
>got a schematic for it (drawn by Bodo Wenzel) for a clone of the Ace, some
>bits are different, 90% of it is the same though.
>
>Thanks.
>--
>Phil.
>philpem_at_dsl.pipex.com
>http://www.philpem.dsl.pipex.com/
>
>
Received on Tue Dec 10 2002 - 17:02:01 GMT

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