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Onan 7.5 JB-3CR running issue


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  #61  
Old 03-20-2017, 11:25:31 PM
mheltunen mheltunen is offline
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Default Re: Onan 7.5 JB-3CR running issue

I did wire up a outlet and when I fired it up the first time I plugged in a trouble light and seemed fine. This is where things went south.....😡. I was fiddling with the carb when the set stalled. I restarted it and it ran rough and bounced around a bit (sitting on a pallet). I did not have the screws for the control box in place (I know...dumb) and it jumped up and the bottom of the board grounded out on the frame of the set...light fireworks 😖. After I put it back in place and installed the screws I re fired it and noticed the light was very dim. I then checked the voltage at the outlet and read between 30-40 volts. Yes the reset switch was tripped and I did reset it before starting the second time. Sometimes when you take shortcuts they come back to bite you.
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  #62  
Old 03-21-2017, 05:24:49 AM
squidtrap squidtrap is offline
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Default Re: Onan 7.5 JB-3CR running issue

Fireworks are never good.
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  #63  
Old 03-21-2017, 07:16:21 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5 JB-3CR running issue

Quote:
Originally Posted by mheltunen View Post
I did wire up a outlet and when I fired it up the first time I plugged in a trouble light and seemed fine.

it jumped up and the bottom of the board grounded out on the frame of the set...light fireworks ��. After I put it back in place and installed the screws I re fired it and noticed the light was very dim.
I have paid for my mistakes more times than I like to admit. Sounds like a new board is in your future.

Are you running it the way it is shown in the pictures in your first post? Just sitting on the oil pan on a pallet? That is a lot of weight on the aluminum pan. You really need to get some vibration isolators under the feet. Even a block of wood with a piece of rubber under the feet would be better than nothing. I once bought a set that had 2" pieces of heavy walled hose about 1 1/2" in diameter under the feet, not perfect, but better than nothing.
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  #64  
Old 03-21-2017, 07:56:25 AM
mheltunen mheltunen is offline
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Default Re: Onan 7.5 JB-3CR running issue

I do need some isolators for the feet. Currently for testing I have been running it as shown. It does appear a board is in my future indeed. I may look at having it repaired or perhaps there are some different options available. Looking at Drawing #612-4794 I have some confusion over the AC terminations. I have been able to identify the T leads so that is a help but I'm unsure how the read the schematic. I intend to run it as 120V 60 HZ. Looking at the drawing to me it appears if I want to use it in this configuration I tie T3 and T1 together and T4 and T2 together and run those out to each side of an outlet to achieve this. If this is the case what is used for a ground if any?

Thanks
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  #65  
Old 03-21-2017, 09:56:44 AM
mheltunen mheltunen is offline
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Default Re: Onan 7.5 JB-3CR running issue

To address my voltage regulator issue I'm considering trying a SX460 as a cost effective solution until I get all the bugs worked out and the fine tuning to the set? Any thoughts on these? Easy install or do they require a lot of custom wiring?
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  #66  
Old 03-22-2017, 05:34:48 AM
squidtrap squidtrap is offline
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Default Re: Onan 7.5 JB-3CR running issue

The wiring should b correct 1+3 tied together for hot and 2+4 together to gen frame for ground, then out to form the neutral.

Just get confirmation on that, its early and eyes play games on me now. Ed.
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  #67  
Old 03-22-2017, 08:34:48 AM
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Jim McIntyre Jim McIntyre is offline
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Default Re: Onan 7.5 JB-3CR running issue

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Originally Posted by mheltunen View Post
To address my voltage regulator issue I'm considering trying a SX460 as a cost effective solution until I get all the bugs worked out and the fine tuning to the set? Any thoughts on these? Easy install or do they require a lot of custom wiring?

Check here:

https://www.smokstak.com/forum/showthread.php?t=139868
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  #68  
Old 03-22-2017, 01:32:53 PM
yellowlister yellowlister is offline
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Default Re: Onan 7.5 JB-3CR running issue

This is the centrifugal switch I have from a jc. I don't have any covers left..
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  #69  
Old 03-22-2017, 02:24:47 PM
mheltunen mheltunen is offline
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Default Re: Onan 7.5 JB-3CR running issue

Update.. I finally have the jb running but much fine tuning and parts will be needed. I have confirmed that the AC side is operational by jumping the f1/f2 leads so I feel a bit better moving forward. I will need a new coil and wires a centrifugal switch and cover, a voltage regulator and isolation feet. I sure appreciate all of the help from everyone and I suspect more may follow.

Thanks,
Mark
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  #70  
Old 03-22-2017, 02:47:28 PM
len k len k is offline
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Default Re: Onan 7.5 JB-3CR running issue

Clean the terminals on coil. My brass ones were mucky and it didn't spark till I cleaned them.

Look on ebay for coil, For alternate coil ideas using modern car/motorcycle coils see my thread
https://www.smokstak.com/forum/showthread.php?t=167037
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  #71  
Old 03-22-2017, 05:35:59 PM
mheltunen mheltunen is offline
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Default Re: Onan 7.5 JB-3CR running issue

I followed your advice and cleaned them well but still no change.

]I have also considered trying one of these : https://www.denniskirk.com/2001766.s...d=154651372798. Thoughts ?
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