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Onan 30 EK Diode set

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Old 12-04-2013, 12:22:20 PM
kapt kapt is offline
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Default Onan 30 EK Diode set

I have a 70's model 30EK with a 240 6 cyl Ford engine. The unit was running fine before it sat for 5 years inside a barn. Engine still runs great but no voltage.. I have went through the service manual and checked everything except the Diodes. After looking at them they appear to be a bit corroded from the storage. The manual says to disconnect them to test. If I have to disconnect them, I may as well replace them..
Where is the best place to ge these ? Onan website doesnt list this unit or any parts..

Contact through email is best since i can rarely get here..

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Old 12-04-2013, 12:34:39 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan 30 EK Diode set

Need to know what you have in order to get you the correct part numbers. Model and serial number.
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Old 12-04-2013, 12:49:52 PM
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Dave Edmonds Dave Edmonds is offline
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Talking Re: Onan 30 EK Diode set

Frankly, I'd test them before replacing them. All you need is an inexpensive volt-ohmmeter (even the Harbor Freight "cheapies" will do). There are quite a number of websites that will show you how to test them (after the first thousand or so, testing is easy!!).
Dave Edmonds
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Old 12-04-2013, 02:55:56 PM
Jim Rankin Jim Rankin is offline
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Default Re: Onan 30 EK Diode set

The diodes should be a stud mount type available from almost any electonics supplier. Mouser, Digikey, ebay sometimes. I didn't sweat the details when I needed to replace some, just ordered the highest PIV and amperage that would fit through the hole in the heat sink. I'm sure a couple hundred volts is plenty on the PIV, but I think I ended up with 400 volt and 20 amp, could have been higher. I know they didn't have the reverse polarity I needed when I was ordering from Mouser, so I bumped my specs up a notch so I could get them shipped the same day from their stock instead of waiting on a back order.

I think mine were Ruttonsha brand and Mouser listed them under "power diodes" I think.

You can take the nut off the stud and pull them out of the heat sink to test, no need to unsolder them just to test. But, you're right, by the time you get into the rotor like that, you probably should just replace them all if any are bad. Once you get the diodes loose, then you can test the main field as well. No sense replacing diodes on an open/shorted field.
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Old 12-04-2013, 04:22:43 PM
kapt kapt is offline
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Default Re: Onan 30 EK Diode set

The Model is: 30 EK-15R 10740D
Ser: 0571305917
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Old 12-07-2013, 02:24:49 PM
processedpower processedpower is offline
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Default Re: Onan 30 EK Diode set

I have onan PNs in my notepad, but they want close to 40 bux a pop X 6...I used NTE 5884s and 5885s for about 10 bux each available at your local electronics house(maybe not the shak) they are working- as long as I can get the propane fuel system to my case, it was the F2 side diodes that were shot- all 3, the F1 side looked ok by the VOM, but changed to matching values as the replacement negative biased diodes...HTH

nte diodes listed are rated at 600 volts/25 amps...3 anode case, 3 cathode case, 40 watt soldering gun, resin core solder- I used tiny needle nose vice grip to hold them just under solder point to dissipate the heat before it reached the diode bodies...
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