X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 11 Feb 2008 18:08:35 -0500 Message-ID: X-Original-Return-Path: Received: from wind.imbris.com ([216.18.130.7] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTPS id 2724850 for lml@lancaironline.net; Mon, 11 Feb 2008 11:42:51 -0500 Received-SPF: none receiver=logan.com; client-ip=216.18.130.7; envelope-from=brent@regandesigns.com Received: from [192.168.1.100] (cbl-238-80.conceptcable.com [207.170.238.80] (may be forged)) (authenticated bits=0) by wind.imbris.com (8.12.11/8.12.11.S) with ESMTP id m1BGg92U019577 for ; Mon, 11 Feb 2008 08:42:09 -0800 (PST) (envelope-from brent@regandesigns.com) X-Original-Message-ID: <47B07AE0.8040907@regandesigns.com> X-Original-Date: Mon, 11 Feb 2008 08:42:08 -0800 From: Brent Regan User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: VM1000 Failure Content-Type: multipart/alternative; boundary="------------020202010204090003020806" This is a multi-part message in MIME format. --------------020202010204090003020806 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Colyn writes <<< While we're on that, I had a situation with a grt eis 6000 (similar to the eau that Chelton sells or used to). One day my MAP started indicating zero concurrently with erratic indications on several of the egt's. On investigating I found that squeezing or moving the wire harness from the probes to the eis caused different erratic indications. Tearing apart the wire harness revealed several spade connectors that weren't connecting anymore. It's also possible that some were shorting to ground via the shielding on adjacent probes. The unexpected (for me) finding was that fixing the egt connections is what made the MAP work again. I would guess there is a way to build a more robust interface to the probes such that badness on one input doesn't cause badness on another. Is there any way I can provide better isolation outside the box? >>> It was likely the terminal to shielding short that was the problem. I have never seen inside a EIS 6000 but I have seen the guts of an EAU (designed and built by GRT). Extrapolating those observations, I would say that it is very likely that there is a long list of things that can be done to harden the system against faults and failures. Most of these would be internal to the electronics box. Your question was about what can be done on the outside. The most obvious one is get rid of the damn spade terminals! Get yourself some silver solder, flux and a jeweler's torch at the local welding store, cut the spades out of the system and splice the thermocouple wire using silver solder and heat shrink. The time you spend doing the splicing right will pay off in spades (npi) by reducing the faston terminal maintenance. Remember, for every spade connection replaced by a splice you are eliminating three failure points, wire to spade, spade male to female and spade back to wire. Remember also that with thermocouples you are dealing in millivolt signal levels. I do not know what wiring is supplied GRT but the VMS came with a pile of Radio Shack spaghetti that quickly found its way into the bin in favor of some aircraft grade MIL-27500/18 tefzel cable. Bottom line. The reliability of any aircraft electronics is highly dependent on the quality of the materials used for the installation and the skill of the technician doing the work. Regards Brent Regan --------------020202010204090003020806 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Colyn writes
<<<

While we're on that, I had a situation with a grt eis 6000 (similar to the eau that Chelton sells or used to).

One day my MAP started indicating zero concurrently with erratic indications on several of the egt's. On investigating I found that squeezing or moving the wire harness from the probes to the eis caused different erratic indications. Tearing apart the wire harness revealed several spade connectors that weren't connecting anymore. It's also possible that some were shorting to ground via the shielding on adjacent probes.

The unexpected (for me) finding was that fixing the egt connections is what made the MAP work again. I would guess there is a way to build a more robust interface to the probes such that badness on one input doesn't cause badness on another. Is there any way I can provide better isolation outside the box?

>>>

It was likely the terminal to shielding short that was the problem. I have never seen inside a EIS 6000 but I have seen the guts of an EAU (designed and built by GRT). Extrapolating those observations, I would say that it is very likely that there is a long list of things that can be done to harden the system against faults and failures. Most of these would be internal to the electronics box.

Your question was about what can be done on the outside. The most obvious one is get rid of the damn spade terminals! Get yourself some silver solder, flux and a jeweler's torch at the local welding store, cut the spades out of the system and splice the thermocouple wire using silver solder and heat shrink. The time you spend doing the splicing right will pay off in spades (npi) by reducing the faston terminal maintenance. Remember, for every spade connection replaced by a splice you are eliminating three failure points, wire to spade, spade male to female and spade back to wire. Remember also that with thermocouples you are dealing in millivolt signal levels.

I do not know what wiring is supplied GRT but the VMS came with a pile of Radio Shack spaghetti that quickly found its way into the bin in favor of some aircraft grade MIL-27500/18 tefzel cable.

Bottom line. The reliability of any aircraft electronics is highly dependent on the quality of the materials used for the installation and the skill of the technician doing the work.

Regards
Brent Regan

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