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Bantam D3 Rectifier testing
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Poshpaws
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January 3, 2019 - 1:15 pm
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I hope someone could give me an accurate way of testing this 6v rectifier?

[Permission to view this image is denied]
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Does anyone have a good spare for sale?

If I wanted to upgrade to a modern equivalent, which wire goes to what as they all appear to be 4 wire options available?

Many thanks[Image Can Not Be Found]

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JulianS
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January 3, 2019 - 2:58 pm
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The pancake rectifier was superseded by the large square one in 1962 so it is probably well past its best.

 

Its 4th connection is to earth.

 

a/c input to the topmost connections in your photo, dc negative is the brown and dc positive the earth connection.

 

The Wipac service bulletin shows the connections. Yours is 3rd illustration down.[Permission to view this image is denied]

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cocorico
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January 3, 2019 - 3:13 pm
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Here's a quote from Wikipedia:

Replacement

Selenium rectifiers had a shorter lifespan than desired. During catastrophic failure they produced significant quantities of malodorous and highly toxic fumes that let the repair technician know what the problem was. By far the most common failure mode was a progressive increase in forward resistance, increasing forward voltage drop and reducing the rectifier's efficiency. During the 1960s they began to be superseded by ** Please log in to view ** They are still manufactured for exact replacement purposes but are not designed into new equipment.

It is safer to replace it with a modern silicon bridge rectifier. The 2 terminals marked ac or ~ go to the alternator, in your case + to chassis, - to battery -.

You need to be certain the -ve connection of the bridge is not connected to it's casing if connecting as +ve earth or you will have a direct short circuit across the output!

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mike p5xbx
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January 3, 2019 - 4:34 pm
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Testing read page G4 of the workshop manual
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connections for the bridge rectifier you just need to add an earth wire
Your Light Greens and White are AC
The brown is DC Negative and the body is Positive

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D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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mike p5xbx
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January 3, 2019 - 4:54 pm
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cocorico said
During the 1960s they began to be superseded by silicon rectifiers which exhibited lower forward voltage drop,
  

actually that can be significant on the D10/14 using original 6Volt without a regulator and using a sealed type battery,
but a good thing with the D1-7 as they struggle to charge the battery anyway
you get over 1volt more output into the battery I have measured over 8.5v on a 10amp Acid battery (on a D14) using a silicon rectifier thats not going to do a small battery much good

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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Poshpaws
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January 4, 2019 - 12:36 pm
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mike p5xbx said
Testing read page G4 of the workshop manual
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connections for the bridge rectifier you just need to add an earth wire
Your Light Greens and White are AC
The brown is DC Negative and the body is Positive

[Permission to view this image is denied]
  

Excellent, Many thanks

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Poshpaws
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January 7, 2019 - 12:07 pm
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mike p5xbx said
Testing read page G4 of the workshop manual
[Permission to view this media is denied]

connections for the bridge rectifier you just need to add an earth wire
Your Light Greens and White are AC
The brown is DC Negative and the body is Positive

[Permission to view this image is denied]
  

I have bought one and It appears to be all good now (not tried to start yet though).

But my + and - battery leads no longer have continuity - which is good!! 

It is handy and tucks in the battery box out of sight.

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Blue Heeler
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January 7, 2019 - 3:24 pm
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How hot do the silicon bridge rectifiers get under normal operating conditions? Not fitted one yet, but have one at the ready in case it`s required during a rebuild. Reason I ask is I often hear of  people tucking them away in the toolbox, wouldn`t they be better off on a heat-sink piece of alloy somewhere more exposed to airflow?

Blue 

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sunny
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January 7, 2019 - 3:55 pm
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hi Blue      its   about  room  temp  i  beleave     so     i  put  mine  on  a large lunp  of      thick   aloy checker plate    in  the  same   place  as  the  old one  &   not  in the  tool   box  

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