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rectifier info please

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Jerry atric View Drop Down
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    Posted: 17 Aug 2018 at 19:34
Sorry, this is only indirectly Guzzi related. i'm asking on here as I know we have some genned up kiddies and I have never seen any bulls**t written (except by me, probably). I am putting a Honda CB175 together and it's missing the selenium rectifier. I have read that these days you just buy any old item and fit it for a few quid. Is this right, does it have be a certain capacity or anything and does it matter where it comes from? If I get the wiring wrong first time round, wile it burn out? is a 12 volt one different to a 6 volt one? I really am useless at electrics Any advice appreciated, thank you. The link to Guzzi is that this Onda is sitting on the work bench and I need to get the Super Alce on there
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 17 Aug 2018 at 21:51
Need a bit more information if you can give it.

A selenium rectifier suggests an older bike. A later silicon one would be better.

BUT, we need to know what sort of alternator, as in how many windings or phases. How many wires come out of it?

So long as you get a rectifier which can handle 12v and the current involved, it doesn't matter if it's a 6 or 12v system.

Assuming you just have 2 AC wires out, then a standard silicone bridge rectifier will work fine, probably better than the selenium. But how is the voltage regulated?


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Motty View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Motty Quote  Post ReplyReply Direct Link To This Post Posted: 17 Aug 2018 at 22:30
It probably isn't any help, but I swopped the separate regulator and rectifier on the RD with a generic modern combined unit.
I think the important bit to remember is the number of wires the combined R/R needs, on the RD I think I needed seven wires
Can you post an image of the relevant section of the wiring diagram?
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Jerry atric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 17 Aug 2018 at 22:32
Thanks Brian, It's a 1974 model. From memory, it has 4 wires. Yes, its missing the voltage reg. as well
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 09:00
Gets a lot more complicated when the voltage reg is also missing.
Have you looked at generic units? Quite a few variations are made.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 09:36
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 11:10
I would probably go for a modern silicon bridge rectifier and Zener diode system as fitted to British bikes of the period. The Zener diode is a little crude (dumps excess voltage as heat) but they work well.

Otherwise something like a Boyer power box would probably do the trick.

I would not expect 3 phases or anything complex on a bike of this year - more likely to be a single phase alternator.

But I don't know the specific bike.
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 11:21
He said there were four wires out of the alternator, doesn't suggest simple single phase. However, I have little knowledge of Honda fitments.

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Jerry atric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 14:02
I've done some surfing around on American Honda pages and it seems it IS a 3 phase alternator. It seems that some model years did not have voltage regulators as the alternator output is only puny. Its wired through the light switch to give more voltage when the lights are on. Does this make sense? There is a modern replacement on Ebay item number 360667342103. Is that the sort of thing you put on your Yamaha Motty?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 14:42
When he said 4 wires I interpreted it as 4 wires connected to the reg/rec. Of course if 4 coming out of the alternator what I suggested would probably be incorrect.

The wiring through the light switch is the sort of thing early British alternator circuits used where one alternator coil was for normal use and 2 more switched in for headlight use. Not a very precise system and it's usually better on them to connect as a 2 wire system. They were still single phase however.

Possibly 2 wires on yours are for normal running and the other two for the lights?

There's a youtube video that may be useful (or not?): https://www.youtube.com/playlist?list=PLCTKEp4J6gEoaI_9KWs0oiS49j8335fuk


Edited by iansoady - 18 Aug 2018 at 14:45
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Motty View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Motty Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 16:37
Originally posted by Jerry atric Jerry atric wrote:

There is a modern replacement on Ebay item number 360667342103. Is that the sort of thing you put on your Yamaha Motty?

That is similar, I have attached a photo of the combined R/R which is now fitted to the RD. (Note if you are a rivet counter please do NOT look at the photograph)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 17:11
I looked, but can't actually see any rivets to count. LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 17:16
If it's wired up through the light switch, then yes, probably switching in more coils, but all of course single phase.
Doesn't make wiring a rectifier in any easier unless you have some knowledge of these circuits.

Any chance we could find a circuit diagram online? what model bike is it exactly?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 17:31
Does this help?



According to that, simple 4-pin bridge rectifier. And the light switch bungs the 3rd alternator coil into circuit for headight.

My second bike was the CD version, only 6V electrics. The CB was posher 'sporty version' with leccy start and (lots) more chrome. A work mate had one.




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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2018 at 17:37
Several CB175 rectifiers on eBay, it seems, I'd get a pristine new one preferably, not a cacky looking old one.



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