DECstation 220 - Out of Ideas?

Chuck Guzis cclist at sydex.com
Sun Jun 25 13:25:27 CDT 2017


On 06/25/2017 09:24 AM, Rob Jarratt via cctalk wrote:

> Thanks Pete, so there is enough of a chance that I have found the
> culprit to make it worth the effort of desoldering it.
> 
> I have been wondering for a while about getting a hot air rework
> station. There are lots of cheap Chinese ones on Ebay. Given my
> likely light use it feels worth getting one at this point. Anyone
> tried one of these:
> http://www.ebay.co.uk/itm/Genuine-WEP-640W-Hot-Air-Gun-Soldering-Rework-Station-Temp-Control-Digital-/112453738508?
> At that price it feels worth the gamble.
When replacing components on an SMD board, I prefer to use a low-temp
fusible alloy such as "Chip Quik":

http://www.chipquik.com/store/

A nice kit, but really, any low temp fusible alloy will work.  I use
Cerrobend as a powder, packed around the IC.

http://www.csalloys.com/specifications.html

I heat the board from the underside with a PAR38 halogen spotlight,
which raises the temperature to around the point where it becomes
uncomfortable to the touch.

The part then just slides off; the IC pads (and the IC itself if you
want to re-use it) can be cleaned with a toothbrush and the continued
application of light heating.

All the parts around the IC are unaffected and soldering a new part is
straightforward.

FWIW,
Chuck



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