IC sockets in aviation equipment

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A friend has asked me to look at a 30-year old aviation radio that
he's had serviced in the past. At that time the technician sprayed and
reseated the various IC sockets. I don't yet have the radio, but I'm
thinking that IC sockets would be an unreliable thing to have in any
aviation application. Does anyone know what the rules are today? BTW,
my understanding is that this radio is a backup that is going into a
privately built aircraft.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: IC sockets in aviation equipment

:A friend has asked me to look at a 30-year old aviation radio that
:he's had serviced in the past. At that time the technician sprayed and
:reseated the various IC sockets. I don't yet have the radio, but I'm
:thinking that IC sockets would be an unreliable thing to have in any
:aviation application. Does anyone know what the rules are today? BTW,
:my understanding is that this radio is a backup that is going into a
:privately built aircraft.
:
:- Franc Zabkar

Franc, I think the equipment design would be covered by Civil Aviation Authority
regulations such as http://www.casa.gov.au/download/orders/cao103/10324.pdf

While there does not appear to be a specific design requirement excluding the
use of IC sockets in such equipment, paragraph 2.10 specifies that the equipment
must continue to be fully operational under conditions of severe vibration and
shock. I think you will find that in order to meet this criterion, aviation
radio manufacturers do not use sockets unless they are absolutely necessary
since the probability of unseated devices would be high. Where a socket is
required it will be of a high reliability type and the component will be firmly
held in by use of mechanical clamps or other means.

Re: IC sockets in aviation equipment
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Authority
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equipment
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cable ties. work great with machine-screw sockets.

Cheers
Terry

Re: IC sockets in aviation equipment
On Thu, 21 Feb 2008 11:00:01 +1100, Franc Zabkar

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I would never use sockets, ever. Sockets are bad, and are never good.
Even in parts that are susceptible to damage they are bad. Sockets
will always let you down. How a piece of aviation gear can be approved
with sockets is beyond me.

Did I mention that sockets are bad?

Re: IC sockets in aviation equipment
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   Then explain the use of IC sockets aboard the International Space
Station's communications systems.  I know they are there, because I
built the radio that was part of the Lockheed-Martin KU band system.

--
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prove it.
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Re: IC sockets in aviation equipment
On Thu, 21 Feb 2008 11:06:02 -0500, "Michael A. Terrell"

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Give me a good reason why? I used to love fixing those boards that
would come in with the super high quality never fail sockets. Flex the
board and reseat the socket, $500bucks thanks.

Re: IC sockets in aviation equipment
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   The reason for using sockets?  They ordered a customized version of
our standard telemetry receiver.  The software for the control panel,
the tuner, and the demodulator was custom for each customer.  One
mistake a lot of people make is using different metals for the IC pins,
and the sockets.  A lot of these units were used in VERY remote
locations, so the firmware was socketed, for field upgrades.  No one
wants to ship a piece of equipment in for a minor upgrade.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
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Re: IC sockets in aviation equipment
On Fri, 22 Feb 2008 20:57:33 +1000, The Real Andy

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I now have the radio, a Narco COM11A, probably built in 1972. The IC
sockets appear to be high quality AMP types but they have all
fatigued. One is so bad that the IC springs out of one side of the
socket without me even touching it. The radio was serviced in Sept
2007 but obviously not properly. I plan to solder all the chips
(Fairchild 9000 series TTL logic) directly to the PCB wherever
possible. Elsewhere I'll use turned pin wire wrap sockets (for
interconnecting two PCBs).

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: IC sockets in aviation equipment
Depends on the socket. The old Augat sockets with machined pins were
excellent - nothing would shake an IC out of them but some of the
cheaper ones weren't so robust.

Alan

Franc Zabkar wrote:
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Re: IC sockets in aviation equipment
On Thu, 21 Feb 2008 16:20:51 +0000, Alan Peake
composed:

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I've seen one printer design where the IC was retained in a machine
socket by soldering the power pins of the IC to the respective pins of
the socket.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: IC sockets in aviation equipment

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It's not so much the chip falling out, its mainly corrosion causing bad
connections. 30 years ago chips were expensive and less reliable, they were
socketed to facilitate replacement especially during factory test. These
days there is no reason to socket any unless they contain firmware that may
need to be updated.



Re: IC sockets in aviation equipment

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The old Augat sockets had "square peg in round hole" for the IC legs
going into the Augat socket.

This worked as well as wire-wrap joints in that it formed a molecular
bond between IC leg and socket hole that was quite reliable.

I can remember environmentally testing Augat socketed PC boards with
very severe vibration and temperature variations. Never had a single
problem with IC-socket connections.

Ross


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