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Post by na1x on Sept 18, 2007 22:22:18 GMT -5
Hi all.  Well, after a lot of research and homework, I have determined that that little part is not what it is called,( resistor/heatsink ), and it is too small to do the job correctly anyway. It's only a 3A diode in putty in an aluminum heatsink ( way too small ) with 2 terminals sticking out. That part will heat up and the resistance goes from 590 ohms ( working fine ) to over 1000 ohms in no time. When that happens, the battery will not get charged. When it cools, the battery will charge again. Here's a permanent fix. Get yourself a 25a 50v full wave rectifier, and an old pentium aluminum heatsink. Connect the red wire to the plus terminal on the rectifier, and the yellow wire to the negative terminal on the rectifier. Use new terminals, or solder the wires. Disregard the other 2 AC terminals on the rectifier. Using the center hole, mount ithe rectifier to the heatsink. Drill a hole in the heatsink, and use a screw to do so. Use a little heatsink compound. Mount it anywhere you want. I made a short wire harness, and mounted it behind the battery under the removeable cover. I can assure everyone that the part that is supplied is junk, and will definitely fail. Good luck all.  |
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Post by brycegtx on Sept 19, 2007 11:14:59 GMT -5
Hello na1x. Can you tell us the part number of the diode that was epoxied in the heat sink? If it was a 3 amp diode and properly heatsinked, it could flow close to 10 amps without burning up as long as the diode junction does not exceed about 250F. Although I agree, it seems that a metal mounted diode would be better. One replacement might be a diode in a TO220 package. The TO220 could probably be put back in the original heat sink.
In testing the diode, a forward resistance of 500 or 1000 ohms does not indicate the condition of the diode. A more useful measurement is the forward voltage drop. A typical diode might be 0.3 to 0.5 volts cold and 0.9 volts at 10 amps. If your meter has a diode setting, use that. Then the forward resistance is 0.5 volts / 3 amps or 0.16 ohms. And the reverse resistance should be much higher. The heat dissipated is 1.5 watts which would be fine for a free air cooled diode of a reasonable size.
Bryce
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Post by na1x on Sept 19, 2007 22:32:45 GMT -5
No numbers on the (powdered part). It could have been even less than 3a. I don't trust some of the foreign engineering decisions. Also with all accessories running, max current flowing is around 5 amps. The 25A bridge works excellent. I drove around all day today, and the charging system now runs sweet, and the regulation is much better now. I went through 2 stock diodes in 3 weeks. They just got too hot
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Joe
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Post by earlwb on Sept 20, 2007 7:03:25 GMT -5
For years, they have had problems with fake or defective parts getting away from the factories.
For example, a factory makes 10,000 diodes and they find the diodes do not meet specs, so they put them in the recycle bin to be sold for recyling. A scraps dealer buys the parts, but instead of grinding them all up to recycle, the dealer sells the parts to a another person. That other person then sells the parts as brand new legit parts to a factory that needs that part for a really good price purported as being surplus unused parts.Then the factory makes up 5,000 units of some kind and the items make it into mainstream useage. Then they find they have a lot of failures out in the field after the fact.
It all started when the parts procurer went for the really good price on a batch of parts that did not come from an approved reliable parts source.
I like the full wave bridge idea, excellent idea.
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Post by Gary on Sept 20, 2007 8:44:06 GMT -5
Earl -
I think you are right on here. There is tremendous pressure on the manufacturers to keep prices down, so I'm sure they look for savings everywhere they can, including using parts from unreliable sources. The rash of diode problems is probably one example, the fuel pump problems probabaly another, and I think I have another, valve stems.
The valve stems on my Viva were incredibly cracked and aged when I first got the scoot. Some people said chalk it up to cheap Chineese rubber, but even with cheap rubber there is no way they could have aged this much in the few months between manufacture and delivery of the scoot - they looked like they were 30 years old or more. Luciano had a similar situation, and I'll bet there are tons of other scoots out there in the same boat. There is no doubt in my mind that the scooter manufacturer was able to get ahold of an 'expired' batch of old valve stems at maybe 10 cents on the dollar, and just used them.
By the way, I don't necessarily 'blame' the manufacturers for this. They must cut costs every way they can to build a 250 cc scoot, ship it to the US and sell it for $2,000 delivered. It is just something us buyers of these cheaper china scoots need to be wary of.
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Post by earlwb on Sept 20, 2007 9:10:43 GMT -5
Yeah I noticed the valve stems on the wheels were going bad pretty fast. I went and got a pair of better valve stems at the Honda dealer. But the price markup is atrocious though.
They long runnning thread I started on my scooter has a good article on replacing the valve stems.
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