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=20
Yep, the Bell System (think telephones)=C2=A0 ago found that "some" current=
flow was necessary to break-down the oxidizationunless the contacts were a=
rranged to wipe or slide across each other when operating..one solution was=
mercury wetted contacts
Jim
On Tuesday, October 20, 2020, 8:19:36 AM PDT, Bob Spidell <bspidell@com=
cast.net> wrote: =20
=20
The late Dave DuBois, who designed the transistor-switch fix, quit doing =
the conversions when he found the reduced voltage cross the points allowed =
them to oxidize. I tried the transil fix, but didn't get much more longevit=
y than a stock points setup with a diode; I do know some have had better lu=
ck with them.
=20
I have a points/diode pump in my BN2 that works well, but I only have a fe=
w hundred miles in the car. I've lost track of what I've got in my BJ8.
=20
Bob
=20
On 10/19/2020 11:31 PM, Kees Oudesluijs via Healeys wrote:
=20
=20
When rebuilding SU electrical fuel pumps I ad a transil (e.g.. 1.5 KE18CA) =
over the points, parallel or in stead of the capacitor if fitted. This redu=
ces the max voltage across the points to 18V instead of several hundreds wh=
en the contact is broken and the points spark.=20
=20
=20
It is also important to clean and polish the points using flower paper (2-3=
000 grid), also when new!!
=20
A transil is more or less a bi-directional Zener diode. They cost next to n=
othing. I buy them in bulk and pay about $0,15 but when buying only one exp=
ect=C2=A0 to pay between $1 and $5. Ebay is an excellent way to source tran=
sils (mainly from China).
=20
A transistor circuit similar to those used in early transistorised ignition=
systems does a similar job by limiting the current through the points
=20
=20
Kees Oudesluijs
=20
=20
=20
=20
Op 20-10-2020 om 07:50 schreef Ray Juncal via Healeys:
=20
=20
I'm rebuilding a couple of early S. U. fuel pumps for my 100. In checking =
my reference files I came across an article from the MG club about adding a=
transistor circuit to reduce the amps across the points. That would keep t=
he points from burning and extend the life of the points. Has anyone on the=
list tried this? The author of the article claims he has 20,000 miles on t=
he conversion and new looking contact points. Thoughts, comments, suggestio=
ns.....
Regards Ray
=20
=20
=20
=20
_______________________________________________
Archive: http://www.team.net/pipermail/healeys http://autox.team.net/archiv=
e
Healeys@autox.team.net
http://autox.team.net/mailman/listinfo/healeys
oo.com
=20
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<html><head></head><body><div class=3D"ydpf7390cecyahoo-style-wrap" style=
=3D"font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px=
;"><div></div>
<div dir=3D"ltr" data-setdir=3D"false"><br></div><div dir=3D"ltr" d=
ata-setdir=3D"false">Yep, the Bell System (think telephones) ago foun=
d that "some" current flow was necessary to break-down the oxidization</div=
><div dir=3D"ltr" data-setdir=3D"false">unless the contacts were arranged t=
o wipe or slide across each other when operating..one solution was mercury =
wetted contacts<br></div><div dir=3D"ltr" data-setdir=3D"false"><br></div><=
div dir=3D"ltr" data-setdir=3D"false">Jim<br></div><div dir=3D"ltr" data-se=
tdir=3D"false"><br></div><div dir=3D"ltr" data-setdir=3D"false"><br></div><=
div dir=3D"ltr" data-setdir=3D"false"><br></div>
=20
</div><div id=3D"ydp44509694yahoo_quoted_3415853370" class=3D"ydp44=
509694yahoo_quoted">
<div style=3D"font-family:'Helvetica Neue', Helvetica, Arial, s=
ans-serif;font-size:13px;color:#26282a;">
=20
<div>
On Tuesday, October 20, 2020, 8:19:36 AM PDT, Bob Spide=
ll <bspidell@comcast.net> wrote:
</div>
<div><br></div>
<div><br></div>
<div><div id=3D"ydp44509694yiv4758235383"><div>
The late Dave DuBois, who designed the transistor-switch fix, quit
doing the conversions when he found the reduced voltage cross the
points allowed them to oxidize. I tried the transil fix, but didn't
get much more longevity than a stock points setup with a diode; I do
know some have had better luck with them.<br clear=3D"none">
<br clear=3D"none">
I have a points/diode pump in my BN2 that works well, but I only
have a few hundred miles in the car. I've lost track of what I've
got in my BJ8.<br clear=3D"none">
<br clear=3D"none">
Bob<br clear=3D"none">
<br clear=3D"none">
<div class=3D"ydp44509694yiv4758235383yqt3136047398" id=3D"ydp44509694y=
iv4758235383yqtfd05758"><div class=3D"ydp44509694yiv4758235383moz-cite-pref=
ix">On 10/19/2020 11:31 PM, Kees Oudesluijs
via Healeys wrote:<br clear=3D"none">
</div>
<blockquote type=3D"cite">
</blockquote></div></div><div class=3D"ydp44509694yiv4758235383yqt313=
6047398" id=3D"ydp44509694yiv4758235383yqtfd01922"><div><p>When rebuilding =
SU electrical fuel pumps I ad a transil (e.g..
1.5 KE18CA) over the points, parallel or in stead of the
capacitor if fitted. This reduces the max voltage across the
points to 18V instead of several hundreds when the contact is
broken and the points spark. <br clear=3D"none">
</p>
<p>It is also important to clean and polish the points using
flower paper (2-3000 grid), also when new!!</p>
<p>A transil is more or less a bi-directional Zener diode. They
cost next to nothing. I buy them in bulk and pay about $0,15 but
when buying only one expect to pay between $1 and $5. Ebay is
an excellent way to source transils (mainly from China).</p>
<p>A transistor circuit similar to those used in early
transistorised ignition systems does a similar job by limiting
the current through the points<br clear=3D"none">
</p>
<p>Kees Oudesluijs</p>
<p><br clear=3D"none">
</p>
<p><br clear=3D"none">
</p>
<div class=3D"ydp44509694yiv4758235383moz-cite-prefix">Op 20-10-2020 =
om 07:50 schreef Ray
Juncal via Healeys:<br clear=3D"none">
</div>
<blockquote type=3D"cite">
</blockquote></div><div><div class=3D"ydp44509694yiv4758235383yahoo=
-style-wrap" style=3D"font-family:Helvetica Neue, Helvetica, Arial, sans-se=
rif;font-size:16px;">
<div dir=3D"ltr">I'm rebuilding a couple of
early S. U. fuel pumps for my 100. In checking my reference
files I came across an article from the MG club about adding
a transistor circuit to reduce the amps across the points.
That would keep the points from burning and extend the life
of the points. Has anyone on the list tried this? The author
of the article claims he has 20,000 miles on the conversion
and new looking contact points. Thoughts, comments,
suggestions.....<br clear=3D"none">
</div>
<div dir=3D"ltr">Regards</div>
<div dir=3D"ltr">Ray<br clear=3D"none">
</div>
</div>
<br clear=3D"none">
<br clear=3D"none">
=20
<br clear=3D"none">
=20
<br clear=3D"none">
</div></div></div><div class=3D"ydp44509694yqt3136047398" id=3D"ydp445096=
94yqtfd54625">_______________________________________________<br clear=3D"n=
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