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Ever notice your rectifier getting hot while running?

Classic Norton Commando Motorcycles.

Ever notice your rectifier getting hot while running?

Postby jimbo » Thu Aug 10, 2017 8:25 pm

My rectifier bolt head got hot to the touch running today, ever notice that?
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Re: Ever notice your rectifier getting hot while running?

Postby L.A.B. » Fri Aug 11, 2017 2:02 am

That's the reason for the 'finned' design.

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Re: Ever notice your rectifier getting hot while running?

Postby Clanger » Fri Aug 11, 2017 6:19 am

Yes also the later square potted bridge type ones without fins get hot too, but its normal.

It would be interesting to see what the spec was, I guess the penny pinchers decided they could do without fins when they made the bridge type, but silicon eventually fails and heat increases the aging process.

I have in the past had one fail on me, - it made a sticky mess.. worth carrying a spare if doing some miles.

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Re: Ever notice your rectifier getting hot while running?

Postby kraakevik » Fri Aug 11, 2017 7:20 am

You have to wonder how much ambient "cool air" there is under the seat, downwind of the engine and next to the oil tank with three quarts of hot oil



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Re: Ever notice your rectifier getting hot while running?

Postby Stillreel » Fri Aug 11, 2017 12:15 pm

kraakevik wrote:You have to wonder how much ambient "cool air" there is under the seat, downwind of the engine and next to the oil tank with three quarts of hot oil


I'm going to install a micro fan for mine.
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Re: Ever notice your rectifier getting hot while running?

Postby lazyeye6 » Fri Aug 11, 2017 12:58 pm

Stillreel wrote:
kraakevik wrote:You have to wonder how much ambient "cool air" there is under the seat, downwind of the engine and next to the oil tank with three quarts of hot oil


I'm going to install a micro fan for mine.



Hmmmm
After 13 years and 15,000 miles on my Commando you've got me worried.
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Re: Ever notice your rectifier getting hot while running?

Postby MexicoMike » Fri Aug 11, 2017 1:50 pm

Silicon and Selenium rectifiers were commonly used in old tube amplifiers where it gets far hotter than it ever will in the Commando. As noted, it's all completely normal for them to be quite warm...even hot. But, obviously if you are uncomfortable with it, a Podtronics is a good replacement. A 1973 rectifier was on mine until '12 with no problems at all. When I installed the Alton E-start I switched to a Podtronics, thinking it might be a better match to the Alton alternator.
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Re: Ever notice your rectifier getting hot while running?

Postby blacklav » Sat Aug 12, 2017 8:58 am

I have a boyer powerbox fitted to mine which does away with all the old lucas bits. It doesn't get hot, so how does the heat dissipate?

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Re: Ever notice your rectifier getting hot while running?

Postby aceaceca » Sat Aug 12, 2017 12:54 pm

I got a few replacements from Radio Shack. Newer design and technology I suspect. Still running the original though on my current bike.
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Re: Ever notice your rectifier getting hot while running?

Postby MexicoMike » Sat Aug 12, 2017 2:27 pm

blacklav wrote:I have a boyer powerbox fitted to mine which does away with all the old lucas bits. It doesn't get hot, so how does the heat dissipate?


It uses diodes to convert the AC from the alternator to DC. Though there is some heat produced, they are much more efficient (less heat) than a Selenium rectifier like the OEM Norton unit.
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Re: Ever notice your rectifier getting hot while running?

Postby L.A.B. » Sat Aug 12, 2017 2:39 pm

MexicoMike wrote:Though there is some heat produced, they are much more efficient (less heat) than a Selenium rectifier like the OEM Norton unit.


The "OEM Norton" rectifier is 'Silicon diode', not Selenium.
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Re: Ever notice your rectifier getting hot while running?

Postby L.A.B. » Sun Aug 13, 2017 12:49 am

blacklav wrote:I have a boyer powerbox fitted to mine which does away with all the old lucas bits. It doesn't get hot, so how does the heat dissipate?


It might not get as hot but the Boyer instructions state;

http://www.boyerbransden.com/pdf/PBOX00108.pdf
Mount unit in free air, this can be in a battery box but some air for cooling is required.


The three-phase Power Boxes also have fins to help keep them cool.
https://www.rgmnorton.co.uk/buy/boyer-p ... r_1885.htm
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Re: Ever notice your rectifier getting hot while running?

Postby MexicoMike » Sun Aug 13, 2017 9:45 am

L.A.B. wrote:
MexicoMike wrote:Though there is some heat produced, they are much more efficient (less heat) than a Selenium rectifier like the OEM Norton unit.


The "OEM Norton" rectifier is 'Silicon diode', not Selenium.


The rectifier (before I replaced it with Podtronics) on on my '73 Commando is a Selenium rectifier, NOT silicon. The difference is very obvious: selenium rectifier plates are square, silicon are round.
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Re: Ever notice your rectifier getting hot while running?

Postby L.A.B. » Sun Aug 13, 2017 11:12 am

MexicoMike wrote:The rectifier (before I replaced it with Podtronics) on on my '73 Commando is a Selenium rectifier, NOT silicon. The difference is very obvious: selenium rectifier plates are square, silicon are round.


Well, it was obviously an older replacement as it wasn't a standard OEM Norton Commando rectifier of any year, as the Silicon 49072 2DS 506 rectifier had replaced the Selenium type on just about all (if not all) British bikes by 1964.

http://www.classicbike.biz/Norton/Parts ... _73-74.pdf
Group 28, Item 31, 49072 Rectifier (2DS 506 Silicon).

http://www.classicbike.biz/Norton/Repai ... mmando.pdf

Section A Electrical
Rectifier type: 2DS 506


Section J4
RECTIFIER TYPE 2DS 506

The rectifier which is of the silicon crystal bridge connected full-wave type.....


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(The '2DV 406' in jimbo's photo is the two-diode 850 Mk3 rectifier for the RM23)
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Re: Ever notice your rectifier getting hot while running?

Postby MexicoMike » Sun Aug 13, 2017 1:17 pm

So somebody replaced a newer silicon rectifier with a much older Selenium rectifier? Certainly it's not impossible but seems very odd. One possibility - I don't know for sure - the bike had the 180W Lucas alternator and the dual zeners/"square" regulator. Perhaps the 180W "kit" included the older regulator? Not sure why that would be the case but maybe so...
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