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'[EE]: RS232 voltage levels (was PIC SBC requiremen'
2000\11\01@045826 by Mike Bob

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While we are at the topic of RS232, I have a problem with the RS232
link between two boards.  I am still investigating.

There are two boards, and they talked to each other through RS232, one
using the LTC1337CS trsansceivers and the other using the SIPEX
SP236ACT.  Both are charge-pump type.  The link between them is short,
a 6 inches (15cm) ribbon cable.  One of the card (the one with
SP236ACT) connects to some other radio equipment (RF stuff).  The two
boards were working OK for last 2 years, but now on some sets the
boards would not talk to each other.  Power off and on would not
recover the link, BUT unplugging and replugging the ribbon RS232 cable
would.

Any ideas what is happening?  I do not know is there a change on the
radio equipment.  The boards are not openly exposed to the RF
equipment, they are in aluminimium case.

Cheers, Ling SM

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2000\11\01@090646 by Olin Lathrop

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face
> The two
> boards were working OK for last 2 years, but now on some sets the
> boards would not talk to each other.  Power off and on would not
> recover the link, BUT unplugging and replugging the ribbon RS232 cable
> would.
>
> Any ideas what is happening?

Yeah, the ribbon cables slowly worked their way loose over two years, the
contacts are starting to corrode, or something similar.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, .....olinKILLspamspam@spam@cognivis.com, http://www.cognivis.com

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2000\11\01@110137 by V sml

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>> The two
> boards were working OK for last 2 years, but now on some sets the
> boards would not talk to each other.  Power off and on would not
> recover the link, BUT unplugging and replugging the ribbon RS232
cable
> would.
>
> Any ideas what is happening?

Olin wrote:
>Yeah, the ribbon cables slowly worked their way loose over two years,
the
contacts are starting to corrode, or something similar.

I forgot to mention that these sets come back after 2 weeks if only
repluggings are done.  No feedback on how many times they are used, or
how they failed?

It is also unlikely due to cable-loose or corrosion.  The plugs are
glued together with hot-gun after fixing.  The pin and sockets are
still shiny gold, no sign of corrosion.

Ling SM

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2000\11\01@112706 by David VanHorn

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>iled?
>
>It is also unlikely due to cable-loose or corrosion.  The plugs are
>glued together with hot-gun after fixing.  The pin and sockets are
>still shiny gold, no sign of corrosion.

The connectors can fail to make contact, even if all is shiny and golden
inside.

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2000\11\01@121515 by Dan Michaels

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Ling SM wrote:
>>> The two
>> boards were working OK for last 2 years, but now on some sets the
>> boards would not talk to each other.  Power off and on would not
>> recover the link, BUT unplugging and replugging the ribbon RS232
>cable
>> would.
>>
>> Any ideas what is happening?
>

What does your oscilloscope say?

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2000\11\01@130418 by V sml

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>>> The two
>> boards were working OK for last 2 years, but now on some sets the
>> boards would not talk to each other.  Power off and on would not
>> recover the link, BUT unplugging and replugging the ribbon RS232
>cable
>> would.
>>
>> Any ideas what is happening?
>

>What does your oscilloscope say?

The 2 sets that I have are unplugged, so I cannot duplicate the
problems.  The first set of data from a tech guy using multimeter show
some constant voltage on the RX and TX.  Only RX and TX are used.  One
of them is +8V.   Look like something freezed up.

I think it is unlikely due to the contact because one of the card
always polls the other card for heartbeat.  A temporarily break would
not cause a freeze, and the contact are of good quality crimp.

I think there would be some returning soon because one guy sent out 10
sets after just replugging.  I would do some probing then.

Ling

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2000\11\01@143432 by Olin Lathrop

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> >Yeah, the ribbon cables slowly worked their way loose over two years,
> the
> contacts are starting to corrode, or something similar.
>
> I forgot to mention that these sets come back after 2 weeks if only
> repluggings are done.  No feedback on how many times they are used, or
> how they failed?
>
> It is also unlikely due to cable-loose or corrosion.  The plugs are
> glued together with hot-gun after fixing.  The pin and sockets are
> still shiny gold, no sign of corrosion.

The pins may be gold plated and nice and shiny, but do you know for sure
that the inside of the connector where the pins mate is also gold plated and
corrosion free?  Sometimes its hard to see this sort of thing visually.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, KILLspamolinKILLspamspamcognivis.com, http://www.cognivis.com

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