AeroElectric-List Digest Archive

Sun 04/11/10


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 03:00 AM - Crowbar OV module part (Phil)
     2. 04:30 AM - Re: HLMP-2685 multi-LEDs off LR3C (James Kilford)
     3. 06:51 AM - Re: Crowbar OV module part (Robert L. Nuckolls, III)
     4. 06:56 AM - Re: Lithium backup power (Robert L. Nuckolls, III)
     5. 07:20 PM - intermittent transponder mystery solved (Bill Boyd)
     6. 10:51 PM - Re: intermittent transponder mystery solved (David LLoyd)
 
 
 


Message 1


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    Time: 03:00:30 AM PST US
    From: Phil <philwhite9@aol.com>
    Subject: Crowbar OV module part
    Bob: The part listed as "MBS4991" is no longer carried by Digi-Key. Mouser lists a possible replacement as a silicon bi-lateral switch by NTE as their part NTE6403. Is this the correct type item? Or is that device something else? Need to build 2 OV modules for my electrically dependent, dual alternator project. Phil RV-10 w/ Mazda 20B rotary engine in IL


    Message 2


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    Time: 04:30:23 AM PST US
    Subject: Re: HLMP-2685 multi-LEDs off LR3C
    From: James Kilford <james@etravel.org>
    Bob, That's great, thank you. It gives me a good place from which to experiment. James On Thu, Apr 8, 2010 at 2:04 PM, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com> wrote: > <nuckolls.bob@aeroelectric.com> > > >> >> >> http://parts.digikey.com/1/parts/681506-led-lt-bar-hi-eff-red-8led-dip-hlmp2685.html >> >> I'd like to hook one of these to the LR3C regulator instead of the >> supplied filament lamp, so that it can go into the annunciator panel >> too. >> >> I've been trying to trace a schematic of Bob's, which I'm sure I've >> seen, of how to use an LED instead of a filament lamp with the LR3C, >> as a starting point. I can't find it, and the resistor values would >> be different in any case, so can anyone throw any light on to how to >> use one of these 8-LED devices with the LR3C? > > The schematic I published is at: > > http://aeroelectric.com/Pictures/Schematics/LR3_LV_Led_1.jpg > > Your application will take some experimentation. > You can try paralleling all the LEDs and seeing how > well you can excite the array and still have uniform > illumination. You may find that you need to treat > them as separate LEDs. > > Just be aware that LR3 lamp driver is never completely > "OFF". The off current is too low to get any light > from a bulb but it will cause an LED to glow at a > reduced intensity. Hence the paralleling resistor to > get the LED to mimic a lamp more closely. > > Bob . . . > >


    Message 3


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    Time: 06:51:50 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Crowbar OV module part
    At 04:57 AM 4/11/2010, you wrote: > >Bob: The part listed as "MBS4991" is no longer carried by Digi-Key. >Mouser lists a possible replacement as a silicon bi-lateral switch >by NTE as their part NTE6403. Is this the correct type item? Or is >that device something else? > > Need to build 2 OV modules for my electrically dependent, dual > alternator project. Those devices have been out of production for many years. We purchased one-time-lifetime-buys to keep our production needs at B&C/AEC going but developed the 2-transistor synthetic trigger diode version illustrated in the DIY data package for when they finally run out. Suggest you consider that version for your project. I'm aware of no suitable replacements for the MBS4991/4992 component. Bob . . .


    Message 4


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    Time: 06:56:30 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Lithium backup power
    At 08:46 PM 4/9/2010, you wrote: >Bob, >You've probably already heard about this. Any comments? > >The huge advancements in lithium battery technology that have >improved consumer products ranging from cell phones and laptop >computers to electric cars will soon arrive in aircraft. >Mid-Continent Instruments recently certified an emergency power >supply known as the MD835, which is designed to keep electric >attitude indicators and other critical avionics working when the >aircraft systems that power them fail. > >Stan Sutterfield > Sure. Li-Ion has been taking hold in emergency back-up batteries for some years. They're particularly well suited to situations that do not call for humongous discharge (cranking) and charge (dual 600A generators) currents. A couple years ago I evaluated the 7V Li-Ion cartridges from one of the famous hand-tool manufacturers . . . pretty good batteries but still a pain in the arse for doing a graceful system integration. My personal design goals will continue to move forward with the notion that it's better to build a failure-tolerant system than patch on emergency back-up band-aids. The artfully crafted, maintained and operated system will not experience an emergency. Bob . . .


    Message 5


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    Time: 07:20:01 PM PST US
    Subject: intermittent transponder mystery solved
    From: Bill Boyd <sportav8r@gmail.com>
    I finally ran to ground my transponder intermittent that has been plaguing me for years! My set-up is a Garmin GTX 320 in a tray that formerly housed a Narco AT-150, using Garmin's plug-and-play adapter to fit between the two. The first time it crapped-out, I sent the transponder back to Garmin: $250 bench fee to be told the box is fine. Worked fine for awhile after that. Then it started becoming intermittent - the interrogation light would flicker normally at the start of a cross-country, and ATC could give me VFR advisory service, but often by the time I got to the destination I was only showing as a primary target on radar. I limped along like this for awhile, but the prospect of having to enter the Orlando mode C veil next week with "known issues" motivated me to try again. I started with what has worked before - removing the transponder and adapter tray, spraying every connection with contact cleaner and reassembling it all. Well, that worked for a few seconds and then it quit again, so I got out the continuity checker and started checking the RF path for opens and shorts. The meter showed an open on the coax center conductor when I wiggled it in the back of thel Narco tray. Put the innards back in, and sure enough, if I held the coax a certain way, I saw interrogation flashes; if I let go, it stopped. Now all I need is for the pax to reach under the panel and hold the coax the whole trip. Not happening. The BNC jack on the transponder itself looked good; the male mating plug on the front side of the adapter looked good - no bent pin. The female jack in the back of the Garmin-to-Narco adapter looked good. There is a small length of RG-184-type teflon coax inside the adapter, but it is totally protected inside the chassis and is under no mechanical strain, and it's new Garmin manufacture, so the problem can't be there <hold that thought> so the fault must be in that ancient RG-58 pigtail that came with the Narco tray and was probably soldered in the 1950's. But the continuity checker showed no opens or shorts no matter how I wiggled it on the bench, and its coax shield is well-crimped and fully strain-relieved. Maybe the male pin on the end of that pigtail, the one that's captive in the back of the tray, is worn/undersize. So I added a thin layer of solder to the gold pin and pressed it back into the fitting on the Garmin adapter tray - still showed an intermittent open when I wiggled it! @#$%! At this point, I noticed that as I twisted the jack into the plug, the shell of the Garmin female (the barrel) would move with it. That's not supposed to happen. In fact, the entire guts of the Garmin female fitting is threaded into its mounting flange, and since it is not secured or safetied in any way (and was doubtless under-torqued at assembly), movement of the male coax pigtail on the outside of the tray eventually broke the BNC solder connection inside the Garmin adapter. I re-threaded the outer shell of the Garmin adapter's female connector with red LocTite and re-soldered the mini-coax to it. Problem fixed - hopefully for good! Moral of the story: never assume that a factory avionics assembly is properly done, or that a wire that "can't possibly" move/break hasn't done just that. I only wish that there was some lifetime warranty where the Garmin would comp me for the time and aggravation this has caused. I'm attaching pictures that show the adapter tray, the fitting as it comes apart but isn't supposed to, and how it broke the solder joint internally. The last one shows the guts of the BNC fitting completely unscrewed from its mounting flange and the coax just hanging there. May this never happen to you! :-) If it does, remember to question everything you're assuming. I'm gonna feel bad if the pictures don't upload - never done that on Matronics list before. -Bill B. / "Stormy" RV-6A


    Message 6


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    Time: 10:51:19 PM PST US
    From: "David LLoyd" <skywagon@charter.net>
    Subject: Re: intermittent transponder mystery solved
    Bill, If you reach the right service engineer at Garmin, repeat the story, I am sure that they would be happy to compensate you and also return the $250 left on their table. I have had issues with Garmin several times in the past, and when the story was told, they were gracious about working with me. Unless things have changed at Garmin, I would take your service problem back to them. They may have an assembly problem or Q/C problem and would want to know about it...... Shouldn't matter if the unit is out of warranty.... If you don't have luck with your first try at the refund, review their management team via the web and write the key guy a detailed letter.... he will make it happen.... David ------------------------------------------------------------------------- ------- ----- Original Message ----- From: Bill Boyd To: rvsoutheast-list@matronics.com ; aeroelectric-list@matronics.com Sent: Sunday, April 11, 2010 7:15 PM Subject: AeroElectric-List: intermittent transponder mystery solved I finally ran to ground my transponder intermittent that has been plaguing me for years! My set-up is a Garmin GTX 320 in a tray that formerly housed a Narco AT-150, using Garmin's plug-and-play adapter to fit between the two. The first time it crapped-out, I sent the transponder back to Garmin: $250 bench fee to be told the box is fine. Worked fine for awhile after that. Then it started becoming intermittent - the interrogation light would flicker normally at the start of a cross-country, and ATC could give me VFR advisory service, but often by the time I got to the destination I was only showing as a primary target on radar. I limped along like this for awhile, but the prospect of having to enter the Orlando mode C veil next week with "known issues" motivated me to try again. I started with what has worked before - removing the transponder and adapter tray, spraying every connection with contact cleaner and reassembling it all. Well, that worked for a few seconds and then it quit again, so I got out the continuity checker and started checking the RF path for opens and shorts. The meter showed an open on the coax center conductor when I wiggled it in the back of thel Narco tray. Put the innards back in, and sure enough, if I held the coax a certain way, I saw interrogation flashes; if I let go, it stopped. Now all I need is for the pax to reach under the panel and hold the coax the whole trip. Not happening. The BNC jack on the transponder itself looked good; the male mating plug on the front side of the adapter looked good - no bent pin. The female jack in the back of the Garmin-to-Narco adapter looked good. There is a small length of RG-184-type teflon coax inside the adapter, but it is totally protected inside the chassis and is under no mechanical strain, and it's new Garmin manufacture, so the problem can't be there <hold that thought> so the fault must be in that ancient RG-58 pigtail that came with the Narco tray and was probably soldered in the 1950's. But the continuity checker showed no opens or shorts no matter how I wiggled it on the bench, and its coax shield is well-crimped and fully strain-relieved. Maybe the male pin on the end of that pigtail, the one that's captive in the back of the tray, is worn/undersize. So I added a thin layer of solder to the gold pin and pressed it back into the fitting on the Garmin adapter tray - still showed an intermittent open when I wiggled it! @#$%! At this point, I noticed that as I twisted the jack into the plug, the shell of the Garmin female (the barrel) would move with it. That's not supposed to happen. In fact, the entire guts of the Garmin female fitting is threaded into its mounting flange, and since it is not secured or safetied in any way (and was doubtless under-torqued at assembly), movement of the male coax pigtail on the outside of the tray eventually broke the BNC solder connection inside the Garmin adapter. I re-threaded the outer shell of the Garmin adapter's female connector with red LocTite and re-soldered the mini-coax to it. Problem fixed - hopefully for good! Moral of the story: never assume that a factory avionics assembly is properly done, or that a wire that "can't possibly" move/break hasn't done just that. I only wish that there was some lifetime warranty where the Garmin would comp me for the time and aggravation this has caused. I'm attaching pictures that show the adapter tray, the fitting as it comes apart but isn't supposed to, and how it broke the solder joint internally. The last one shows the guts of the BNC fitting completely unscrewed from its mounting flange and the coax just hanging there. May this never happen to you! :-) If it does, remember to question everything you're assuming. I'm gonna feel bad if the pictures don't upload - never done that on Matronics list before. -Bill B. / "Stormy" RV-6A




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