[TenTec] QRP T-Kits and IC sockets

[Dr. Gerald N. Johnson, P.E.]

In some Tentec boards (1209 for certain) there's no plated through holes
so component leads often serve to connect top and bottom ground planes.
This is tougher to do with sockets.

Most of the common sockets these days use tin as a contact material.
Against tin its not too bad for logic level. For small signal RF and
audio its terrible. It ages open.

TI makes some very reasonably priced sockets that have a gold inlay in
the their face contact area. They work well. I think they fit IC leads
better than screw machine socket contacts which really are better suited
for round leads than flat leads.

Despite the fact that you may working on an HF radio some IC's have
transistors in them with Ft in the Ghz range and the length of ground
leads can be critical to keeping them from oscillating. This may even be
true of audio output ics. Ft is inversly proportional to transistor area
among other things and in the goal to increase the number of chips from
a wafer transistor sizes do get squashed.

Whenever I have to remove a chip from a board, I nearly always put in a
socket so its easier the next time. Never seems like that socketed chip
fails, but I'm ready just in case.

When removing a chip that's soldered in, don't save it. You've already
determined its bad. Use flush cutting diagonal cutters to cut the leads
from the package. Then remove them from the baord one at a time with a
hot soldering iron and small nosed pliers or sturdy tweezers. There's
far less board damage that way than from trying to get ALL the leads
unsoldered at the same time. Then use solderwick or a solder sucker to
empty the solder from the holes to make room for the socket.

73, Jerry, K0CQ

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