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RX-7 Alternator mod - negative spike diode needed?

 
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finn.lassen(at)verizon.ne
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PostPosted: Tue May 26, 2020 8:01 am    Post subject: RX-7 Alternator mod - negative spike diode needed? Reply with quote

I modified the RX-7 Mitsubishi alternator (reman 14910?) to require external field voltage.

[img]cid:part1.C444B6EB.DBFCBAE3(at)verizon.net[/img]
Connection between three small rectifier diodes and the internal regulator unsoldered, regulator tab bent up and covered with heat shrink, just for good measure.
Very, very simple modification and the internal regulator is still used.
[img]cid:part2.35048761.458E805A(at)verizon.net[/img]
Sorry for they very poor picture from the Haynes RV-7 manual.

So, I feed the field winding from main bus, via a 5A alternator pull-breaker to the EM-36 spade terminal on the alternator.

After my OV crowbar blew up, I took a closer look and am now wondering if I should add a diode from ground to the EM-36 field winding terminal to curb any negative spike.

Normally, without the mod, any negative spike resulting from powering the field winding would be absorbed by the three small diodes and rectifier diodes going to ground.

And perhaps I should also a diode in series with the wire from the breaker to the alternator field terminal so a positive spike from the field winding won't trigger the OV module?

BTW, the alternator does have a built-in capacitor over the output (B+) not shown on the schematic, but visible to the right in the photo and from the outside of the alternator, but doesn't affect the voltage regulator.

Finn


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finn.lassen(at)verizon.ne
Guest





PostPosted: Wed May 27, 2020 9:28 am    Post subject: RX-7 Alternator mod - negative spike diode needed? Reply with quote

I modified the RX-7 Mitsubishi alternator (reman 14910?) to require external field voltage.

[img]cid:part1.5B93539B.AA7D8CFD(at)verizon.net[/img]
Connection between three small rectifier diodes and the internal regulator unsoldered, regulator tab bent up and covered with heat shrink, just for good measure.
Very, very simple modification and the internal regulator is still used.
[img]cid:part2.2B2A573F.52F1A1E1(at)verizon.net[/img]
Sorry for they very poor picture from the Haynes RV-7 manual.

So, I feed the field winding from main bus, via a 5A alternator pull-breaker to the EM-36 spade terminal on the alternator.

After my OV crowbar blew up, I took a closer look and am now wondering if I should add a diode from ground to the EM-36 field winding terminal to curb any negative spike.

Normally, without the mod, any negative spike resulting from powering the field winding would be absorbed by the three small diodes and rectifier diodes going to ground.

And perhaps I should also a diode in series with the wire from the breaker to the alternator field terminal so a positive spike from the field winding won't trigger the OV module?

BTW, the alternator does have a built-in capacitor over the output (B+) not shown on the schematic, but visible to the right in the photo and from the outside of the alternator, but doesn't affect the voltage regulator.

Finn


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List



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