Selenium Retifier Replacement with Solid State Rectifier

[Snakeoil]

Here is an easy way to solve your burnt out/defective charging system rectifier, using either components from Radio Shack or your local electronics salvage or retail business.
The wiring diagram is below and the following page shows the components as assembled by Scott Kirn and forwarded to me for the benefit of Honda fans everywhere.
(For the Honda 90’s substitute pink for brown on the diagram)

Scott used a surplus bridge rectifier (KBPC2505), rated at 25 amps, plus a suitable heat sink. Total cost was less than $5. The mount bolt is a standard 6mm x 30mm bolt in this case. There is a possibility that engine vibration could cause the one-side mount to fail or loosen. A loose (ungrounded) rectifier is NOT a good thing. An alternate mounting method could be to use a longer threaded bolt or a piece of “all-thread” from a hardware store to allow a full mounting on both sides of the bracket. Mounting on both ends of the bracket will dissipate the heat better, as well. Use of a full sized mount bolt will allow for central mounting of the rectifier and wiring.
When attaching the charging system wiring, either make up some adapter wires to match the OEM wiring ends to the spade mount terminals or just cut the ends of the wires and crimp/solder the terminal ends on securely. Try to use the correct size wire gauge terminals. With Scott’s central ground terminal, you must be careful not to allow the ends of the terminal to touch any of the adjacent terminals. Obviously, this would ground out any AC or DC voltages at the rectifier, causing a loss of charging system output at the very least. Run a short jumper wire from the central ground terminal to the Neg (-) terminal on the rectifier, to complete the chassis to rectifier ground circuit.
This system will work for most 1960s Honda twins and 90cc singles, using a full-wave rectifier system w/o regulator. Even the half-wave circuits in the smaller 50-65cc machines can use the same hardware, using just one of the AC terminals, instead of two.
Happy Charging! Bill Silver www.vintagehonda.com

Sample courtesy of Scott Kirn

[geosar]

I bought and wired one of the Radioshack rectifiers many years ago before I forgot about my CL77 for many years.

I am not clear on how to exactly install the device on the frame. Mount the rectifier single bolt onto one of the two mounting brackets where the original rectifier went or what?

Does it need to be mounted on a paint free part of the frame?

Help.

Thank you very much

George
Arizona

[Snakeoil]

Here is the finished mounting bracket which also doubles as a heat sink. I made this from 1/8" alum sheet stock.

Note that the picture of the sink alone is slightly different than how it looks in the picture with the rectifier mounted on it. I had to trim that back side down a bit so I could mount it as shown in the pictures of the assembly installed on the bike. The length of the sink when finished was about 2-1/8" x 1-5/8", the narrower of the two being the width between the mounting ears on the bike frame.

The only visible portion is the end of the sink sticking out below the side covers. The original could be seen as well and you really have to get down on your knees to see it when the bike is sitting on it's stand.

regards,
Rob

[geosar]

That's perfect. Sort of what I imagined.

On it this week.


George

[Narly9999]

OK the two wires from the ac stator. Does it matter which side of this rectifier they go to? And why dosn't the third wire from the stator go to the rectifier? That dosen't seem right. WHy?

Also, I used a computer heat sink with some sink greese and added a 12v ball berring mini fan. =-) lol Drilled the center of the heat sink for the mounting screw for the retifier. Haven't fully mounted the unit securely to the frame as yet but plan on something that's astheticly pleasing. The fan and sink are factory black like the bike so it looks pretty good.

I'm only getting 12.23v +/- .5v When the bike is on it has less voltage then when I turn it off. ON it's as said above and when off it climbs to 12.40 +. Any possible reason for this? It was exactly the same before I switched out the Rectifier. So I don't think it was my rectifier causing this issue. Hmmmmm<<<<,

Thanks ! ;)

[brewsky]

OK the two wires from the ac stator. Does it matter which side of this rectifier they go to? And why dosn't the third wire from the stator go to the rectifier? That dosen't seem right. WHy?

quote]
The brown and yellow wires go to the rectifier.
The pink wire goes to the ignition switch and connects back to the yellow wire when in the "lights on position".
There is a wiring diagram and switch matrix sticky in the Electrical section.
Here:
http://www.honda305.com/forums/viewtopic.php?t=6088

[Snakeoil]

Narrly,

When you do these mods, you need to do more than just look at the diagram or read the instructions on how to do the mod. You should study the wiring diagram and understand not only what you are modifying, but how the system works so you can double check your work to make sure you've done thing correctly, you can find the problem if it does not work correctly and finally, if there is an error in the diagram or instructions you don't reproduce the same error when you do the mod. I've caught errors on factory diagrams and instructions over the years.

For your voltage difference, if you are talking with the ign on and off, and not the motor running or not running, then I would expect the voltage to drop with the ign on and the engine not running. If the voltage drops with the engine running, then I would say that you do not have any charging current going into the battery. With your DMM connected across the batt terminals, if you rev the engine and the voltage goes down as the revs go up, you are not charging your battery. You are running a total loss system, which means you have battery power only.

Put an ammeter between the positive lead and the battery (in other words, in series) with the engine off and once connected and all things properly insulated to prevent shorts against the frame, start the bike and see if you have positive current flow into the battery. If not, then you need to make sure the rectifier is connected properly and if so, then check the separate output leads from the alt with your DMM set on AC voltage. I have not checked, but would expect the manual has an alternator testing procedure.

The other side of the coin is the general consensus is that the charging system is more of a battery maintenance system and with the lights off, you don't see much current going into the battery. I've never investigate this, but I've read plenty of posts here on the subject. Search the electrical threads and you'll probably find them.

regards,
Rob