DECstation 220 - Out of Ideas?

Rob Jarratt robert.jarratt at ntlworld.com
Sun Jun 25 11:24:29 CDT 2017



> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Pete
> Turnbull via cctalk
> Sent: 25 June 2017 16:12
> To: cctalk at classiccmp.org
> Subject: Re: DECstation 220 - Out of Ideas?
> 
> As soon as I saw "74LS125" I thought, "Oh, yes, another one".  That's a fairly
> early design tri-state buffer, and in my experience they're not very robust.  We
> used to replace lots of those, though admittedly I'm referring to the DIL
> version.  Worth checking it out.
> 
> If you can't desolder all the SMD pins, try this trick: for each side, thread a
> piece of enamelled copper wire under the chip near the pins.
> Tie or wrap one one to some nearby component and hold the other end in your
> hand.  Starting at the end with the wire you're holding, heat each pin with your
> soldering iron, and drag the wire under it, thereby breaking its contact with the
> board.
> 
> Failing that, apply a tiny amount of flux to the pins, and heat it up with a hot air
> gun, preferably a temperature-controlled one, and lift it off with forceps (or flip
> it over with a small screwdriver).
> 


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.

Regards

Rob



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