Electrical Question

Hi Guys

I know a diode allows current to flow in one direction only and that it's purpose is to protect electrical components. Which components does the diode under the seat protect on the XJ range of bikes and why are there diodes in the rectifier regulator unit? Finally what are the correct spark plug caps to use so that the ignitor does not get damaged?

 

The principle component of a rectifier is the diodes. They convert the AC current to DC. The other diodes may be protecting against accidental reverse polarity.

 

So the DC is used to charge the battery and run the bikes electrical system. As it is a three phase alternator producing AC current I assume the rectifier has three diodes Bluegray57?

 

6 i expect. Do some googling, simple electrical theory is out there. Essentially though a rectifier only conducts one way, so with an ac wave it will chop either the top or the bottom of it off. Put two of them on the same wire and you can seperate top and bottom halves, hence double the voltage. If you have three ac waves at different points in their cycles you can have three times the power (but not the voltage), if you have enough diodes.
The "blocking" diodes are to seperate different DC circuits, preventing interferance between one and another.
Don't know the answer on plugs or plug tops, but I suspect one or the other, but not both should be resistor type - 5k ohms total? Someone here will know?

 

For more than you likely wanted to know about rectifiers: https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/rectifier-circuits/
But, scroll down to where it says "Three-phase full-wave bridge rectifier circuit" and that's what the diode block in the bike looks like. In cars, those diodes are built into the alternator.

 

Per your question about sparkplug caps for the bike. I'm pretty sure it is bike model and size dependent. If you post your bike model in your signature, that would help.

 

Thanks you all for the information.

 

Actually there needs to be a regulator (hence rectifier/regulator) in there as well, which prevents the DC voltage going high enough to boil the battery and pop the bulbs.
The problem with generators is that the faster they spin, the higher the voltage that comes out of them, hence you need a regulator.

 

yup, I did forget to mention the regulator!

 

Plug caps are relatively universal for all CDI ignition systems, 5k ohm resistance, most air cooled bikes to reach down into the head use NGK XB05FP tall cap, with no terminal nut on spark plug. (One less thing to come loose) 05 representing resistance in thousands of ohms.
Any 5kohm cap will work if it can be fitted to the plug without pulling on the wire and will not damage electrical components. (My two outers are LB05EP short cap 90 degree with nut on plug) as the PO cut the wires short
Note: the caps are screwed into the wire, don't just yank em out!

 

Minimutly it is a combined unit then, the rectifiers diodes to changing AC current to DC and the regulator to stop voltage getting too high. As for the plug caps Colin that was what I was concerned about potential damage to electrical components. Thanks for your feedback guys.

 

the diodes in the regulator turn the ac sine wave into a dc square wave

ac voltage goes runs positive then negitive .

 

https://www.electronics-tutorials.ws/diode/diode_6.html


http://www.play-hookey.com/ac_theory/power_supply/ps_rectifiers.html

 

i think the others probably answered your question. I was trained in electronics/electrical theory years ago but am not specifically knowledgeable in the xj systems.

 

You can use resistor plugs and plain caps without harming the TCI. Just keep the resistance value the same.

 

Yes Bluegray57 a lot of great information from the XJ group on the electrical system. Your training will be transferrable as you know regarding bikes, for me an awareness of how it all works is a great help in troubleshooting.

 

Yes k-moe the TCI units are getting harder to get. The cost of a new unit in comparision with the cost of transistors for the old unit is a lot. I read somewhere that the transistors are not that expensive which I assume break the live feed to the coils the way the old points used to do. Good info on the plugs and caps.

 

Are the units stripable? Ie can you get at the board? Normal practice is to fix the heatsinks then bury it in conformal coating.
If they are accessible it shouldn't be hard to get upgraded transistors to fix them. Is there enough demand though?

 

I think the board is sealed but you can get at it with careful cutting with a knife blade into the back of the case. There is a writeup on here about the Yamaha Vision where the ignition system is similar. Some of the other XJ group will have a better idea how to fix them than I do but I think there are suitable transistors available. There are also a few companies making replacement units some are programmable and some not.

 

http://www.jetav8r.com/Vision/IgnitionFAQ.html

 

Yep. Potted boards. There are new TCI units being made by at least two independent companies, but they cost a bit.

 

I put pictures on the forum last year of that home made TCI, it works well.

 

Replacement TCI Transistors


http://www.xjcd.org/TCI_repair

 

Have you repaired a TCI XJ550H? I would like to try and repair one.

 

no I only have 1 bad tci in my box of spares. I would like to find someone to split cost of transistors and capacitors and try to repair one.
It looks easy enough to do

 

I've done enough electrical repair over the years, that I'm open to trying this. I also have the equipment (a nice quality soldering/desoldering station). Cost of parts should be pretty low (like <$15), but I haven't gone shopping yet, so that's a guess.

 

It is probably easier than I think, I am a carpenter. But I have basic electrical knowledge due to working on vehicles over the years but that is about it. It looks like it is replacing some components and resoldering dry joints where necessary.

 

If any of you do a repair a video of the repair would be brilliant if you have the time to do it? Carmo Electronics charge a lot of money for a replacement unit dKavanagh. The components for the repair should not cost much.

 

Hmm, would be good to have a forum expert. I've done plenty of board repairs but never seen a duff tci. I'd be happy to have a go at it.