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Discussion Starter · #1 ·
While I'm STILL awaiting a specific specification on an output pin so I can finish up the PC board design for the variable speed fan controller (due to popular demand some wanted me to increase the current output capability of the FAULT indicator) as you can see I finished the carb sync design and I wrote up a preliminary BOM for the CDI exact replacement. Since I need to make a couple of prototype PC boards by hand for another "one off" personal project I'll have enough PC board photo developer mixed up that instead of wasting it I may as well try to prove that I've got the correct components chosen to make an exact CDI replacement. It should end up being cheap and while it won't solve a stator problem it should end up being a ton less than an Ignitech unit if only your CDI is out - besides that some people are paying upwards of $200 on eBay for a used CDI module.

Here's the schematic and bill of materials, I don't have a layout for the PC board yet:

All this has been finalized from the little bit and pieces I've gathered over the past two years.

I drew up an easier to read schematic and found part #s for the correct (I hope) values.

I will eventually lay out a PC board and make a prototype to test but in theory it should work.

I'll assume that CAL134 should be set to around 134 ohms and CAL167 to 167 ohms as starting points.

These were apparently put in there to adjust the turn on sensitivity of the main SCRs then never removed from the original prototype once the ideal values were found, and since the units were built and potted long before they went on the bikes so there would have been no way to adjust them afterwards - in other words you could probably just replace CAL134 & R24 with a single 95 ohm resistor and CAL167 & R27 with a single 75 ohm resistor. I'll leave the pots in circuit when I lay it out as the original SCRs are NLA and the ones I chose may have gate sensitivities that are a bit higher or lower than the originals.

Anyhow feel free to make your own PC board using FR4 epoxy-glass material. (not phenolic due to the voltages)

I would not try to build this circuit on a piece of perfboard.

The reason for SCRC is unknown, I don't know why they didn't just make both triggering circuits equal and I've got too much on my plate already to be messing about with redesigning the fool thing, if it works with the original design so be it.
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