- Capacitive discharge ignition circuits - 4 Updates
- Precision Fidelity C7 preamp schematic please - 1 Update
| bob prohaska <bp@www.zefox.net>: Sep 25 04:03AM Does anybody know of links to well-informed descriptions of how AC capacitive discharge ignition circuits work? The case at hand is a 1986 Suzuki DT4 outboard motor. It's a 2-stroke 1-cylinder 4 HP engine, probably not much different in ignition requirements from any other small engine. It uses two bar-style pickup coils, one to charge the cap and one 180 degrees away to fire the plug. The CDI box is distinct from the pickup coils, all are distinct from the ignition coil. Parts are no longer available. There's a photo at http://www.zefox.net/~bp/dt4/PXL_20210923_005603433.jpg The initial diagnosis was an open ignition coil, but a replacement produced one spark and nothing more. Maybe the new ignition coil killed the CDI unit, or maybe we're barking up the wrong tree entirely. With a better idea how it worked in general, there might be a chance at identifying some other engine with compatible parts, or, in the best case, of identifying and fixing the trouble. At this point it appears the two coils in the photo are functional. Thanks for reading, and any ideas! bob prohaska |
| Phil Allison <pallison49@gmail.com>: Sep 24 10:17PM -0700 bob prohaska wrote: ================ > parts, or, in the best case, of identifying and fixing the > trouble. At this point it appears the two coils in the photo > are functional. ** I used to work on CDIs back in the 70s for a kit retailer. Those ones use a pair of 2N3055s in a self oscillating inverter to produce 300VDC. Then an SCR to fire a charged 1uF poly cap into the vehicle's coil. The usual points controlled SCR firing - so a bit different to a 2 stroke OB. However, the commonest failure was the 1uF cap. It had to be a special, high pulse current type to survive at all. Oil filled, metal can ones were good - if you can find any. Otherwise a " polypropylene " fluoro PF correction cap would be OK too. ...... Phil |
| Mike S <mscir@yahoo.com>: Sep 25 02:01AM -0700 On 9/24/2021 9:03 PM, bob prohaska wrote: > are functional. > Thanks for reading, and any ideas! > bob prohaska Part numbers https://www.megazip.net/zapchasti-dlya-lodochnyh-motorov/suzuki/dt4-2462/dt4-8058/dt4-vg-767164/electrical-13320932 |
| Wond <lost@the.ether.net>: Sep 25 03:20PM On Sat, 25 Sep 2021 04:03:41 +0000, bob prohaska wrote: > the two coils in the photo are functional. > Thanks for reading, and any ideas! > bob prohaska ISTR there's one in the venerable GE semiconductor manual |
| Tim Schwartz <tim@bristolnj.com>: Sep 25 08:11AM -0400 On 9/23/2021 5:22 PM, Phil Allison wrote: > https://www.canuckaudiomart.com/details/649678917-fidelity-research-c7-a-preamp/images/2987480/ > .... Phil Thanks Phil, That is exactly what I needed. Regards, Tim |
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