17 May
2001
17 May
'01
1:45 p.m.
If height gets to be a problem, you can take a 0.30" wide header and solder it
onto the bottom of a 0.6" wide part by spreading the contacts on the header.
That lowers the profile considerably and solves the pin-spacing problem too, as
once they're spread by bending themout at 90 degrees, they'll just barely reach
the pins that are folded underneath the IC. Also, if you solder an SMT part
onto a 0.6" header, that combination is often not only lower but cheaper too.
Dick
----- Original Message -----
From: "Pete Turnbull" <pete(a)dunnington.u-net.com>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, May 17, 2001 5:22 PM
Subject: Re: 74xx orgin
On May 17, 22:11, Tony Duell wrote:
:-) A solution I've seen is more "three-dimensional". Take one 24-pin
0.3"-wide wirewrap socket. Bend the pins so they fit into a 0.6"-wide
socket. Fit new IC to "upper" socket and fit this to the "lower"
one. If
liked, mould "power bulge" into the hood. Or cut ventilation hole.
--
Pete Peter Turnbull
Network Manager
University of York
> Yes, a common pitfall. I got bitten by that
:-) And the 74150 has
the
> same number and arrangement of pins as the
74ALS150, but one is 0.6"
wide
and the
other is 0.3" wide!
Most of the 24 pin chips in the 'modern' familes (things like the 74F181
and 74HC154) are 0.3" wide. The 'traditional' ones (74181, 74S181,
74LS154, etc) are 0.6" wide. Don't ask how I found that out.
Suffice it to say I have commerical instruments where the PCB was set out
for a 0.6" wide chip. In said space is a header plug, soldered to which
is the 0.3" 'modern' version with the pins bent out sideways.