[RFI] RFI & Alternator Replacement

Christopher Brown cbrown at woods.net
Sat Sep 23 03:17:09 EDT 2017


An old school externally regulated alternator with a _mechanical_
regulator is very, very noise.

This is because there is a electromechanical "vibrator" pulsing the
field coils.

If you have an external regulator that buzzes, go straight to the
auto-parts store and get a solid state replacement (simple analog
control loop, no pulsing).

I had to do this for the 74 ford trunk I picked up this summer.

Any modern internally regulated alternator should have a solid state
analog regulator.

6 v.s. 12 diode...12 spreads the load and is generally a sturdier/mor
reliable alternator.  IIRC, a dual bridge may or may not produce less
ripple depending on internal construction of the alternator itself.


1 wire v.s. normal....


One wire alts depend in residual magnetism to self-excite.

Normal alts take an ignition switched power feed to start the alternator
then self-excite after that.

If a one wire sits long enough it will not self-excite...And you need to
pull a cover and feed it power to start it up.


If you have a 80s GM you already have a "standard" alternator with a DC
+ output and a 2 pin connector.


By all means, get a dual bridge high wuality internally regulated
alternator, but get a standard type not a one wire.

If you look at the listed vendor, they have similar dual bridge non one
wire models with a std GM connector...get one of those.  Inspect the 2
wire connector, if corroded you can get a replacement for < $5 and just
about any auto parts store.

_Carefully_ connecting a 1uF high current rated cap in parallel with a
1000pf cap between the alt output post and case ground will greatly
reduce ripple as well but you must be CAREFUL as this is a 70-250 amp
alt output.

And remember to replace the alternator cable if you oversize...A 80amp
factory alt may one have 8 or even 10 gauge wire for a charge lead.  I
just replaced a 2ft 10ga charge lead with 4ga.  IIRC mid 80s GM
trucks/subs had a 8ga charge lead, marginal for a 140amp or better
alternator (I had a 1984 3/4t Suburban with a 350 and a 170amp
alternator around 2000 or so)


Again, if you need to ask about a one wire, do not use...eventually it
will fail to self excite and you will not automatically know how to
revive...One wires are for the parts built street rod, IF you are too
lazy to run a single 16ga ignition switched lead...And in your case you
can get a drop in unit as your rig already has the wiring.



On 9/21/17 17:46, qrv at kd4e.com wrote:
> Is a dual-bridge rectifier, as described here re. efficiency
> and durability http://faqs.alternatorparts.com/ also a better
> choice versus RFI or no?
> 
> I just read through this http://www.k0bg.com/alternator.html
> 
> And am looking at these 
> https://alternatorparts.com/10si-12si-high-output-alternators.html
> 
> Thanks - DavidC KD4E
> 
>> Is there any difference in the type of alternator installed
>> and mobile RFI?
>>
>> I'm looking at this for my 1986 Suburban:
>> https://play.google.com/store/apps/details?id=ngd.p_0001
>>
>> Is a "self-exciting" 1-wire design potentially problematic?
>>
>> If so - your recommendations, please?
>>
>> And, no, I could care less about the chrome.
>>
>> Thanks & 73, DavidC KD4E
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