---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 07/30/05: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:22 AM - Diode orientation (Charlie Brame) 2. 10:12 AM - Re: Diode orientation (Charlie England) 3. 10:17 AM - Re:A Bugger of an Avionics Problem (Peter Davidson) 4. 10:30 AM - Re: Diode orientation (chad-c_sip@stanfordalumni.org) 5. 01:56 PM - Re: Re:A Bugger of an Avionics Problem (Wayne Sweet) 6. 03:08 PM - Summing up OVP () 7. 04:16 PM - Re: Summing up OVP (Richard Riley) 8. 06:51 PM - Re: Re:A Bugger of an Avionics Problem (Charlie England) 9. 07:28 PM - Re: Re:A Bugger of an Avionics Problem (Wayne Sweet) 10. 08:12 PM - Re: Summing up OVP (Ken) 11. 11:32 PM - Re: Summing up OVP (Thomas Johnson) ________________________________ Message 1 _____________________________________ Time: 08:22:40 AM PST US From: Charlie Brame Subject: AeroElectric-List: Diode orientation --> AeroElectric-List message posted by: Charlie Brame Bob, et al, My Navaid installation manual recommends a diode between the Navaid pin 7 and the Comm PTT circuit. The Navaid schematic shows a black and white diode with a large white area and a small black stipe on one end. The white area is oriented toward the Comm unit and the black stripe oriented toward the PTT circuit. However, the diode I received from B&C is mostly black with a small grey stripe at one end. Can I assume that the large black end of the diode equates to the large white end on the Navaid schematic? Charlie RV-6A N11CB San Antonio ________________________________ Message 2 _____________________________________ Time: 10:12:34 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Diode orientation --> AeroElectric-List message posted by: Charlie England Charlie Brame wrote: >--> AeroElectric-List message posted by: Charlie Brame > >Bob, et al, > >My Navaid installation manual recommends a diode between the Navaid pin >7 and the Comm PTT circuit. The Navaid schematic shows a black and white >diode with a large white area and a small black stipe on one end. The >white area is oriented toward the Comm unit and the black stripe >oriented toward the PTT circuit. However, the diode I received from B&C >is mostly black with a small grey stripe at one end. > >Can I assume that the large black end of the diode equates to the large >white end on the Navaid schematic? > >Charlie >RV-6A N11CB >San Antonio > Hi Charlie, Just focus on the stripe. The drawing is white because it's simpler to represent the diode as a line drawing of a rectangle rather than a solid black one. The 'business end' always has the stripe. another Charlie ________________________________ Message 3 _____________________________________ Time: 10:17:27 AM PST US From: "Peter Davidson" Subject: AeroElectric-List: Re:A Bugger of an Avionics Problem --> AeroElectric-List message posted by: "Peter Davidson" Wayne, I'm not familiar with the TX760/TN200D system, but it sounds like two possibilities to me. 1) If the harness had to be rewired at all for the new components, there's a good possibility that the coax might have been accidentally yanked on or something to cause problems with the connection. 2) If the new components were direct replacements, I 'd say it's a defective TN200D. -Peter > > I have dual VOR/ILS's; a GNS430 and a recently installed replacement TX760/TN200D. > The VOR/GS is taken from a single VOR antenna through a 1 into 4 splitter. > The Terra is a replacement for an older TX720/TN200, which function well, except > for a squelch problem that Toronto Avionics fixed. I sold that system on eBay. > Anyway, this "new" Terra will not consistantly display the CDI for VOR/LOC EXCEPT > when outbound from the ILS. Then I get turned around and inbound on the ILS, > the TN200D only displays the GS. The GNS430 is rock solid out and inbound. The > old TN200 did not have this problem; it and the GNS430 were working fine. > Also, now the Terra TN200D will not display the CDI for the VOR unless I'm almost > on the airport; VOR on airport. The TRI-NAV is wired to display the OBS setting > as well as the radial currently on. This works OK, meaning the CDI is getting > the correct data. > The only explanation I can come up with, is that the TN200D is less sensitive than > the old TN200 and outbound the "rabbit ears" antenna, oriented with the "ears" > facing aft and under the tailcone has better reception going away from the > ILS. This is weird; all airplanes I have seen have the VOR antenna "facing" > aft. In addition I was told by an avionics shop that dual VOR/ILS typically use > a 1-into-4 quadaplexer, rather than two VOR antennas.. > Has anyone experienced like symtoms?? > Wayne ________________________________ Message 4 _____________________________________ Time: 10:30:46 AM PST US From: chad-c_sip@stanfordalumni.org Subject: Re: AeroElectric-List: Diode orientation Z-USANET-MsgId: XID674JgdREa0184X28 --> AeroElectric-List message posted by: chad-c_sip@stanfordalumni.org yes. Diodes are always marked on their downstream side. But the marking is not necessarily uniform. ------ Original Message ------ From: Charlie Brame Subject: AeroElectric-List: Diode orientation > --> AeroElectric-List message posted by: Charlie Brame > > Bob, et al, > > My Navaid installation manual recommends a diode between the Navaid pin > 7 and the Comm PTT circuit. The Navaid schematic shows a black and white > diode with a large white area and a small black stipe on one end. The > white area is oriented toward the Comm unit and the black stripe > oriented toward the PTT circuit. However, the diode I received from B&C > is mostly black with a small grey stripe at one end. > > Can I assume that the large black end of the diode equates to the large > white end on the Navaid schematic? > > Charlie > RV-6A N11CB > San Antonio > > > > > > > ________________________________ Message 5 _____________________________________ Time: 01:56:17 PM PST US From: "Wayne Sweet" Subject: Re: AeroElectric-List: Re:A Bugger of an Avionics Problem --> AeroElectric-List message posted by: "Wayne Sweet" Peter, Thanks for the reply. I replaced the coax at the tray, using new TED connectors rather than the funky Terra ones. I have done lots of avionics wiring and learned to continuity check all coax connectors. These are fine. The same problem occurs when I plug in a second (and 3rd) TN200D. I bought 3 Terra NAV/COM on eBay, so have some that will be going up on eBay, starting this afternoon. The problem is the same for all 3 TN200D. The coax connections and continuity are fine. Very puzzling. Wayne ----- Original Message ----- From: "Peter Davidson" Subject: AeroElectric-List: Re:A Bugger of an Avionics Problem > --> AeroElectric-List message posted by: "Peter Davidson" > > > Wayne, > I'm not familiar with the TX760/TN200D system, but it sounds like two > possibilities to me. > 1) If the harness had to be rewired at all for the new components, there's > a > good possibility that the coax might have been accidentally yanked on or > something to cause problems with the connection. > 2) If the new components were direct replacements, I 'd say it's a > defective > TN200D. > -Peter > > >> >> I have dual VOR/ILS's; a GNS430 and a recently installed replacement > TX760/TN200D. >> The VOR/GS is taken from a single VOR antenna through a 1 into 4 >> splitter. >> The Terra is a replacement for an older TX720/TN200, which function well, > except >> for a squelch problem that Toronto Avionics fixed. I sold that system on > eBay. >> Anyway, this "new" Terra will not consistantly display the CDI for >> VOR/LOC > EXCEPT >> when outbound from the ILS. Then I get turned around and inbound on the > ILS, >> the TN200D only displays the GS. The GNS430 is rock solid out and >> inbound. > The >> old TN200 did not have this problem; it and the GNS430 were working fine. >> Also, now the Terra TN200D will not display the CDI for the VOR unless >> I'm > almost >> on the airport; VOR on airport. The TRI-NAV is wired to display the OBS > setting >> as well as the radial currently on. This works OK, meaning the CDI is > getting >> the correct data. >> The only explanation I can come up with, is that the TN200D is less > sensitive than >> the old TN200 and outbound the "rabbit ears" antenna, oriented with the > "ears" >> facing aft and under the tailcone has better reception going away from >> the >> ILS. This is weird; all airplanes I have seen have the VOR antenna > "facing" >> aft. In addition I was told by an avionics shop that dual VOR/ILS > typically use >> a 1-into-4 quadaplexer, rather than two VOR antennas.. >> Has anyone experienced like symtoms?? >> Wayne > > > ________________________________ Message 6 _____________________________________ Time: 03:08:46 PM PST US From: Subject: AeroElectric-List: Summing up OVP --> AeroElectric-List message posted by: AeroElectric-List message previously posted by: Richard Riley <<..........skip.......The problem is X It can occur when using equipment Y, under the following conditions - If you use equipment Z instead, it won't happen......skip.......>> 7/30/2005 Hello Richard, I think that your questions are right on target. I'd like to take a layman's whack at answering them: A) "The problem is X" The problem is potential damage to an aircraft's electrical, avionics, or instrument components from an alternator that is putting out excessive voltage. B) "It can occur when using equipment Y......" It can occur when using either an internally regulated or an externally regulated field controlled alternator or a permanent magnet alternator. C) "under the following conditions" When the voltage regulator (either external or internal) or the alternator suffers a fault that causes the over voltage condition. D) "If you use equipment Z instead, it won't happen" There is no way to guarantee that, "it", the over voltage condition, will never happen with any type of regulator or alternator. So the discussion moves onto the ongoing thread of how to best protect an aircraft's electrical, avionics, or instrument components from an alternator that is putting out excessive voltage. 1) Case one: Use an externally regulated field controlled alternator and a mechanism that when an over voltage conditon is detected cuts off the field current to the field controlled alternator. 2) Case two: But what if one doesn't feel that just cutting off the field current provides adequate protection? Then put a separate cut off mechanism in the externally regulated alternator's output B (for battery) lead that opens up that lead in time to protect the components at risk. 3) Case three: But what if the voltage gets so high so quickly that the separate B lead cut off mechanism cannot do its job in time? How high and how quick and the best kind of B lead cut off mechanism is what the ongoing thread is all about. 4) Case four: Use an internally regulated alternator and depend upon the internal regulator to not permit an over voltage condition. 5) Case five: But what if the internal regulator fails to provide adequate protection? Then put a separate cut off mechanism in the internally regulated alternator's output B (for battery) lead that opens up that lead in time to protect the components at risk. 6) Case six: But what if the voltage gets so high so quickly that the separate B lead cut off mechanism cannot do its job in time? How high and how quick and the best kind of B lead cut off mechanism is what the ongoing thread is all about. 7) Case seven: Use a permanent magnet alternator and put a separate cut off mechanism in the permanent magnet alternator's output B (for battery) lead that opens up that lead in time to protect the components at risk. 8) Case eight: But what if the voltage gets so high so quickly that the separate B lead cut off mechanism cannot do its job? How high and how quick and the best kind of B lead cut off mechanism is what the ongoing thread is all about. So where should one's comfort level reside? Mine stops at Case one, but I am not trying to push that down any one's throat. OC ________________________________ Message 7 _____________________________________ Time: 04:16:09 PM PST US From: Richard Riley Subject: AeroElectric-List: Re: Summing up OVP --> AeroElectric-List message posted by: Richard Riley Bob, thank you. I think I'm with you at (1), at lest until a (2) is productized and well distributed. At 03:07 PM 7/30/05, bakerocb@cox.net wrote: >1) Case one: Use an externally regulated field controlled alternator >and a mechanism that when an over voltage conditon is detected cuts >off the field current to the field controlled alternator. > >2) Case two: But what if one doesn't feel that just cutting off the >field current provides adequate protection? Then put a separate cut >off mechanism in the externally regulated alternator's output B (for >battery) lead that opens up that lead in time to protect the >components at risk. > >3) Case three: But what if the voltage gets so high so quickly that >the separate B lead cut off mechanism cannot do its job in time? How >high and how quick and the best kind of B lead cut off mechanism is >what the ongoing thread is all about. > >4) Case four: Use an internally regulated alternator and depend upon >the internal regulator to not permit an over voltage condition. > >5) Case five: But what if the internal regulator fails to provide >adequate protection? Then put a separate cut off mechanism in the >internally regulated alternator's output B (for battery) lead that >opens up that lead in time to protect the components at risk. > >6) Case six: But what if the voltage gets so high so quickly that >the separate B lead cut off mechanism cannot do its job in time? How >high and how quick and the best kind of B lead cut off mechanism is >what the ongoing thread is all about. > >7) Case seven: Use a permanent magnet alternator and put a separate >cut off mechanism in the permanent magnet alternator's output B (for >battery) lead that opens up that lead in time to protect the >components at risk. > >8) Case eight: But what if the voltage gets so high so quickly that >the separate B lead cut off mechanism cannot do its job? How high >and how quick and the best kind of B lead cut off mechanism is what >the ongoing thread is all about. > >So where should one's comfort level reside? Mine stops at Case one, >but I am not trying to push that down any one's throat. > >OC ________________________________ Message 8 _____________________________________ Time: 06:51:54 PM PST US From: Charlie England Subject: Re: AeroElectric-List: Re:A Bugger of an Avionics Problem --> AeroElectric-List message posted by: Charlie England Seems pretty unlikely that all would have exactly the same problem. Can you swap antenna cables at the radio trays, fly & try it? Ohm meter checks of coax will detect only gross problems like DC shorts between center & ground. If you can't swap antennas, rig up a cable with a 'rubber ducky' & try that to see if you have a different symptom. Another possibility is that the radios aren't seating all the way into the tray or the connector. Are you screwing in the chassis retaining screw all the way & making sure that radio goes all the way into the tray? Is this the version of the Terra with 2 separate radios + the 'trinav' head? If so, there are several opportunities for poor/intermittant connections at the various connectors. Slight variations in connector mounting & chassis cutouts can prevent the sub-d connectors from seating all the way & lead to truly bizarre symptoms. The same thing applies to the mating coax connectors between the radios & the tray. If the tray has shifted in the instrument panel, or if the new radios have trim bezels from a different batch/mfgr, or , the radio might not be going all the way into the tray. Charlie Wayne Sweet wrote: >--> AeroElectric-List message posted by: "Wayne Sweet" > >Peter, >Thanks for the reply. I replaced the coax at the tray, using new TED >connectors rather than the funky Terra ones. I have done lots of avionics >wiring and learned to continuity check all coax connectors. These are fine. >The same problem occurs when I plug in a second (and 3rd) TN200D. I bought 3 >Terra NAV/COM on eBay, so have some that will be going up on eBay, starting >this afternoon. >The problem is the same for all 3 TN200D. The coax connections and >continuity are fine. >Very puzzling. >Wayne >----- Original Message ----- >From: "Peter Davidson" >To: >Subject: AeroElectric-List: Re:A Bugger of an Avionics Problem > > > > >>--> AeroElectric-List message posted by: "Peter Davidson" >> >> >>Wayne, >>I'm not familiar with the TX760/TN200D system, but it sounds like two >>possibilities to me. >>1) If the harness had to be rewired at all for the new components, there's >>a >>good possibility that the coax might have been accidentally yanked on or >>something to cause problems with the connection. >>2) If the new components were direct replacements, I 'd say it's a >>defective >>TN200D. >>-Peter >> >> >> >> >>>I have dual VOR/ILS's; a GNS430 and a recently installed replacement >>> >>> >>TX760/TN200D. >> >> >>>The VOR/GS is taken from a single VOR antenna through a 1 into 4 >>>splitter. >>>The Terra is a replacement for an older TX720/TN200, which function well, >>> >>> >>except >> >> >>>for a squelch problem that Toronto Avionics fixed. I sold that system on >>> >>> >>eBay. >> >> >>>Anyway, this "new" Terra will not consistantly display the CDI for >>>VOR/LOC >>> >>> >>EXCEPT >> >> >>>when outbound from the ILS. Then I get turned around and inbound on the >>> >>> >>ILS, >> >> >>>the TN200D only displays the GS. The GNS430 is rock solid out and >>>inbound. >>> >>> >>The >> >> >>>old TN200 did not have this problem; it and the GNS430 were working fine. >>>Also, now the Terra TN200D will not display the CDI for the VOR unless >>>I'm >>> >>> >>almost >> >> >>>on the airport; VOR on airport. The TRI-NAV is wired to display the OBS >>> >>> >>setting >> >> >>>as well as the radial currently on. This works OK, meaning the CDI is >>> >>> >>getting >> >> >>>the correct data. >>>The only explanation I can come up with, is that the TN200D is less >>> >>> >>sensitive than >> >> >>>the old TN200 and outbound the "rabbit ears" antenna, oriented with the >>> >>> >>"ears" >> >> >>>facing aft and under the tailcone has better reception going away from >>>the >>>ILS. This is weird; all airplanes I have seen have the VOR antenna >>> >>> >>"facing" >> >> >>>aft. In addition I was told by an avionics shop that dual VOR/ILS >>> >>> >>typically use >> >> >>>a 1-into-4 quadaplexer, rather than two VOR antennas.. >>>Has anyone experienced like symtoms?? >>>Wayne >>> ________________________________ Message 9 _____________________________________ Time: 07:28:17 PM PST US From: "Wayne Sweet" Subject: Re: AeroElectric-List: Re:A Bugger of an Avionics Problem --> AeroElectric-List message posted by: "Wayne Sweet" Correct. The only remaining component is the antenna. Since the ILS displays strong OUTBOUND as far as 30 miles, but on inbound and only when very near the LOC center, the LOC CDI indicator drops out. The same happens with the VOR CDI most of the time. I will check the balum on the "rabbit ears" antenna, in the event some corrosion has built up to the point that a split signal is too weak for the TN200D, but NOT for the GNS430 ILS. It is strong anywhere within 30 miles of the ILS airport. Hate to have to crawl into the tailcone to access this grounding point. Wayne ----- Original Message ----- From: "Charlie England" Subject: Re: AeroElectric-List: Re:A Bugger of an Avionics Problem > --> AeroElectric-List message posted by: Charlie England > > > Seems pretty unlikely that all would have exactly the same problem. Can > you swap antenna cables at the radio trays, fly & try it? Ohm meter > checks of coax will detect only gross problems like DC shorts between > center & ground. If you can't swap antennas, rig up a cable with a > 'rubber ducky' & try that to see if you have a different symptom. > > Another possibility is that the radios aren't seating all the way into > the tray or the connector. Are you screwing in the chassis retaining > screw all the way & making sure that radio goes all the way into the > tray? Is this the version of the Terra with 2 separate radios + the > 'trinav' head? If so, there are several opportunities for > poor/intermittant connections at the various connectors. Slight > variations in connector mounting & chassis cutouts can prevent the sub-d > connectors from seating all the way & lead to truly bizarre symptoms. > The same thing applies to the mating coax connectors between the radios > & the tray. If the tray has shifted in the instrument panel, or if the > new radios have trim bezels from a different batch/mfgr, or , the > radio might not be going all the way into the tray. > > Charlie > > Wayne Sweet wrote: > >>--> AeroElectric-List message posted by: "Wayne Sweet" >> >> >>Peter, >>Thanks for the reply. I replaced the coax at the tray, using new TED >>connectors rather than the funky Terra ones. I have done lots of avionics >>wiring and learned to continuity check all coax connectors. These are >>fine. >>The same problem occurs when I plug in a second (and 3rd) TN200D. I bought >>3 >>Terra NAV/COM on eBay, so have some that will be going up on eBay, >>starting >>this afternoon. >>The problem is the same for all 3 TN200D. The coax connections and >>continuity are fine. >>Very puzzling. >>Wayne >>----- Original Message ----- >>From: "Peter Davidson" >>To: >>Subject: AeroElectric-List: Re:A Bugger of an Avionics Problem >> >> >> >> >>>--> AeroElectric-List message posted by: "Peter Davidson" >>> >>> >>>Wayne, >>>I'm not familiar with the TX760/TN200D system, but it sounds like two >>>possibilities to me. >>>1) If the harness had to be rewired at all for the new components, >>>there's >>>a >>>good possibility that the coax might have been accidentally yanked on or >>>something to cause problems with the connection. >>>2) If the new components were direct replacements, I 'd say it's a >>>defective >>>TN200D. >>>-Peter >>> >>> >>> >>> >>>>I have dual VOR/ILS's; a GNS430 and a recently installed replacement >>>> >>>> >>>TX760/TN200D. >>> >>> >>>>The VOR/GS is taken from a single VOR antenna through a 1 into 4 >>>>splitter. >>>>The Terra is a replacement for an older TX720/TN200, which function >>>>well, >>>> >>>> >>>except >>> >>> >>>>for a squelch problem that Toronto Avionics fixed. I sold that system on >>>> >>>> >>>eBay. >>> >>> >>>>Anyway, this "new" Terra will not consistantly display the CDI for >>>>VOR/LOC >>>> >>>> >>>EXCEPT >>> >>> >>>>when outbound from the ILS. Then I get turned around and inbound on the >>>> >>>> >>>ILS, >>> >>> >>>>the TN200D only displays the GS. The GNS430 is rock solid out and >>>>inbound. >>>> >>>> >>>The >>> >>> >>>>old TN200 did not have this problem; it and the GNS430 were working >>>>fine. >>>>Also, now the Terra TN200D will not display the CDI for the VOR unless >>>>I'm >>>> >>>> >>>almost >>> >>> >>>>on the airport; VOR on airport. The TRI-NAV is wired to display the OBS >>>> >>>> >>>setting >>> >>> >>>>as well as the radial currently on. This works OK, meaning the CDI is >>>> >>>> >>>getting >>> >>> >>>>the correct data. >>>>The only explanation I can come up with, is that the TN200D is less >>>> >>>> >>>sensitive than >>> >>> >>>>the old TN200 and outbound the "rabbit ears" antenna, oriented with the >>>> >>>> >>>"ears" >>> >>> >>>>facing aft and under the tailcone has better reception going away from >>>>the >>>>ILS. This is weird; all airplanes I have seen have the VOR antenna >>>> >>>> >>>"facing" >>> >>> >>>>aft. In addition I was told by an avionics shop that dual VOR/ILS >>>> >>>> >>>typically use >>> >>> >>>>a 1-into-4 quadaplexer, rather than two VOR antennas.. >>>>Has anyone experienced like symtoms?? >>>>Wayne >>>> > > > ________________________________ Message 10 ____________________________________ Time: 08:12:03 PM PST US From: Ken Subject: Re: AeroElectric-List: Summing up OVP --> AeroElectric-List message posted by: Ken I don't think anyone has spoken of any failure mode that would justify case 2. I believe a B-lead contactor has only been proposed in conjunction with an internal VR alternator. Ken bakerocb@cox.net wrote: >--> AeroElectric-List message posted by: > >AeroElectric-List message previously posted by: Richard Riley > > ><<..........skip.......The problem is X >It can occur when using equipment Y, under the following conditions - >If you use equipment Z instead, it won't happen......skip.......>> > >7/30/2005 > >Hello Richard, I think that your questions are right on target. I'd like to >take a layman's whack at answering them: > >A) "The problem is X" > >The problem is potential damage to an aircraft's electrical, avionics, or >instrument components from an alternator that is putting out excessive >voltage. > >B) "It can occur when using equipment Y......" > >It can occur when using either an internally regulated or an externally >regulated field controlled alternator or a permanent magnet alternator. > >C) "under the following conditions" > >When the voltage regulator (either external or internal) or the alternator >suffers a fault that causes the over voltage condition. > >D) "If you use equipment Z instead, it won't happen" > >There is no way to guarantee that, "it", the over voltage condition, will >never happen with any type of regulator or alternator. So the discussion >moves onto the ongoing thread of how to best protect an aircraft's >electrical, avionics, or instrument components from an alternator that is >putting out excessive voltage. > >1) Case one: Use an externally regulated field controlled alternator and a >mechanism that when an over voltage conditon is detected cuts off the field >current to the field controlled alternator. > >2) Case two: But what if one doesn't feel that just cutting off the field >current provides adequate protection? Then put a separate cut off mechanism >in the externally regulated alternator's output B (for battery) lead that >opens up that lead in time to protect the components at risk. > >3) Case three: But what if the voltage gets so high so quickly that the >separate B lead cut off mechanism cannot do its job in time? How high and >how quick and the best kind of B lead cut off mechanism is what the ongoing >thread is all about. > >4) Case four: Use an internally regulated alternator and depend upon the >internal regulator to not permit an over voltage condition. > >5) Case five: But what if the internal regulator fails to provide adequate >protection? Then put a separate cut off mechanism in the internally >regulated alternator's output B (for battery) lead that opens up that lead >in time to protect the components at risk. > >6) Case six: But what if the voltage gets so high so quickly that the >separate B lead cut off mechanism cannot do its job in time? How high and >how quick and the best kind of B lead cut off mechanism is what the ongoing >thread is all about. > >7) Case seven: Use a permanent magnet alternator and put a separate cut off >mechanism in the permanent magnet alternator's output B (for battery) lead >that opens up that lead in time to protect the components at risk. > >8) Case eight: But what if the voltage gets so high so quickly that the >separate B lead cut off mechanism cannot do its job? How high and how quick >and the best kind of B lead cut off mechanism is what the ongoing thread is >all about. > >So where should one's comfort level reside? Mine stops at Case one, but I am >not trying to push that down any one's throat. > >OC > > > > ________________________________ Message 11 ____________________________________ Time: 11:32:38 PM PST US From: "Thomas Johnson" Subject: AeroElectric-List: Re: Summing up OVP --> AeroElectric-List message posted by: "Thomas Johnson" > >--> AeroElectric-List message posted by: Ken > > >I don't think anyone has spoken of any failure mode that would justify > >case 2. I believe a B-lead contactor has only been proposed in > >conjunction with an internal VR alternator. > >Ken > This is my understanding as well. There are really only two "lightning rod" issues here: 1) Crowbar disconnect method VS other methods a) AEC has recommended the crowbar method for shutting down both internally and externally regulated alternators. b) Some say that the crowbar method is outdated and that there are better ways to implement this function. c) Some say that the crowbar method is hazardous due to the low internal resistance of modern batteries. d) I have yet to see a published schematic for any alternative to the AEC crowbar module. e) False triggering will be an "issue of scrutiny" with any disconnect method. 2) B-Lead disconnect & load dump issues a) AEC has recommended a B-lead overvoltage disconnect ONLY for internally regulated alternators. b) It has been shown that a B-lead disconnect can cause a "load dump" event. c) It has been shown that a load dump event can damage some alternators. d) It has been claimed that the installation of Transorbs in the right places can mitigate this problem. Tom Johnson