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Old 18-09-2009, 10:02   #1
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Getting Alternator Diodes

Hi would anyone know how to get diodes for an alternator.

I have an amptech 125SE alternator, and last week the output noticeably dropped. I pluged in my spare 100 amp alternator and it worked good.
Same external regulator was driving both alternators so I am pretty sure its the amptech atylernator.

I cleaned the brushes, and sliprings, made sure there's no dust on the windings, did all the winding resistnace tests.
What makes me think its the diodes is the AC ripple
On an amptech alternater I get about 1.1V ac ripple at 75% or rated RPM.
On my spare 100AMP alternator the ripple is barely noticeable.

Petar
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Old 24-09-2009, 16:01   #2
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Just thought I put my findings for others to use...
Amptech s125E uses motorola pres-fit 50amp diodes. They are 1/2" in size.
Set is 3 pairs, and can be replaced pretty easy.
Also getting a higher rating diodes would help alternator durability in damp and hot engine rooms.
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Old 24-09-2009, 16:03   #3
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I would replace the entire regulator with one of known high quality.
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Old 24-09-2009, 16:39   #4
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Originally Posted by David M View Post
I would replace the entire regulator with one of known high quality.
David,

He said he has an external regulator. The Diodes are internal to the alternator (they rectify the alternators output).
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Old 24-09-2009, 16:50   #5
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Woops...your right.
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