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Onan JC Stumper


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  #21  
Old 11-27-2016, 10:09:32 AM
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Default Re: JC Stumper

Captain, I have a MDJB 1966 vintage. The magnaciter toasted when the unit ran out of fuel under a load. I searched for a replacement back I 1998 the only one I could find was from ONAN I had limited internet and searches turned up nothing else. I bought the ONAN replacement It has been perfect .
Today I would try a imported sx 40 avr cheep replacement
good luck
Bob
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  #22  
Old 11-27-2016, 11:03:32 AM
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Default Re: JC Stumper

The SX460 isn't rated to deliver the current needed by a magniciter set's field.

This one claims to be good for 15A, but as I recall, the mangeciter fields needs even more than that. Still, it might be a good starting point for some experiments.
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  #23  
Old 11-27-2016, 01:26:59 PM
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Default Re: JC Stumper

Jim I have looked into a number of the generic chinese regulators and no matter what the model number implies it usually turns out that the unit is only rated for 5 A or so. Sometimes it will say a few more amps for 10 secs or so peak but inevitably it is less than what is required for a magneciter. I was surprised to see that the direct from Onan replacement for the magneciter existed. I have never seen it come up in the years I have been watching the Stak. Cheers Dan
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  #24  
Old 11-27-2016, 05:55:43 PM
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Default Re: JC Stumper

Thanks for all the information everyone.

So my plan is to disconnect the magniciter/regulator and then troubleshoot the generator starting. Replace the regulator with the one recomended. Once it starts and runs perfect at 1800 rpm, I'll test the current magniciter/regulator and see if it is actually toast, replace components or replace the whole thing.

It'll be a few days, but I'll update the status.
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  #25  
Old 09-11-2017, 01:08:59 PM
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Default Re: JC Stumper

Sorry, for the long delay. Yesterday, I added the Garretson regulator behind the fisher 622 regulator. The Generator starts perfectly and stabilizes at 1800 rpm. Problem 1 is Fixed.

The second problem is that in about 2-3 minutes the Magnacitor/voltage regulator starts smoking. I believe we all agreed it is toast because of Problem 1.

So now I have a decision to make.

The Onan direct replacement is now $1,427.

The Powertronics listed below is cheaper 700ish, but I'm concerned about rewiring it.

Has anyone used the Powertronics regulator with success? I'd rather spend the $1,427 and be sure I did it correctly, than inadvertently screw something up trying to convert the Powertronics just to save $700.

With that being said I'm willing to save $700 if it is a fairly strait forward conversion.

V/R,
captainjdog


Quote:
Originally Posted by EricWood View Post
Thats an Onan static exciter/regulator assembly that replaced the old Magneciter guts.

Hold on to your seat.... The static unit alone listed in 2015 for $1063. The "kit" listed for $1345.

Powertronics, has a universal regulator (XR8) and a static exciter module (SEM250A) for a combined total of $733.

http://www.power-tronics.com/technic...intechpage.htm

Sending the attachment along as a little help and reference for what you have. Apologies for splitting it in half--was a little to large for allowed upload as a single document.
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  #26  
Old 09-11-2017, 02:13:26 PM
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Default Re: JC Stumper

The powertronics has a good reputation and they do make even higher power addon static exciters for their VR. I would have reasonable confidence in their products. There is an other approach that you may wish to consider. A complete YD genend from a newer JC would bolt on to your engine. There are a few kicking around out there and I suspect that that would be a lot cheaper than the Onan replacement and possibly even the Powertronics unit. The last one I bought ran me $400 plus shipping. You would need a VR on top of that but the SX460 works fine on a YD gen end and there is even room in the control box for it. For that matter a complete JC can sometimes be found quite reasonable. Something to consider. Cheers Dan
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Old 09-11-2017, 03:10:51 PM
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Default Re: JC Stumper

Dan

Thanks for offering option C. I get annoyed when blind myself between to 2 options, and then someone informs me of an obvious alternative that I didn't even consider.

V/R,
Justin
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  #28  
Old 09-11-2017, 06:51:53 PM
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Default Re: JC Stumper

I have a SX1N3B magneciter complete that I will never use. I believe this is correct for your set. I can look it up in the parts manual if you are interested to be sure.

It can be yours for the cost of postage.

In checking the master parts book to be sure of which exciter your set was built with, I am not finding an exact model match. I am using the model # in post 3 of this thread. Can you double check the model number?

Last edited by Max Thompson; 09-12-2017 at 07:08:45 AM.
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  #29  
Old 09-12-2017, 11:45:03 AM
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Default Re: JC Stumper

Max,

Wow! I'm blown away by your kindness. I'm definitely interested. PM Sent.

V/R,
Justin
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  #30  
Old 09-12-2017, 04:07:24 PM
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Default Re: Onan JC Stumper

Max's offer is really good, but I have a model 808 in my magniciter 7.5jb

https://www.flightsystems.com/standb...regulator.html

just another option
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  #31  
Old 09-14-2017, 07:37:16 AM
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Default Re: Onan JC Stumper

I found the build sheet and looks like the 06SX1N3B is the correct exciter.

Build sheet and diagram should be attached.
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  #32  
Old 09-14-2017, 08:36:19 AM
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Default Re: Onan JC Stumper

Quote:
Originally Posted by Max Thompson View Post
I found the build sheet and looks like the 06SX1N3B is the correct exciter.

Build sheet and diagram should be attached.
Sounds like plug and play that's very generous Max. Would you do any testing to see what happened to the old one before installing the new one. Maybe there's some tests.
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  #33  
Old 09-14-2017, 09:31:52 AM
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Default Re: Onan JC Stumper

Before you replace the Magneciter you should measure the the field resistance, both stationary and running in case you have a "flying short" that only shows up with the engine running. I would also check for a short to ground under both conditions.

I would go a little farther myself and use a variable power supply to power the field. Let it run for a couple of hours both unloaded and at full load while monitoring field voltage and current.

There is no use putting a good part on and have it blow up in case of a short in the revolving field winding.
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  #34  
Old 09-14-2017, 10:57:22 AM
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Default Re: Onan JC Stumper

Kevin,
I agree, my second biggest fear would be to burn up the new unit. First being, electrocuting myself.

I'm familiar with most electronics and components and terminology. I worked on quite a few gas/diesel generators through the years, but it’s usually the mechanical end. Working on the electrical end is a first for me and it seems to deal with stuff I’m not custom to, like field resistance.

I was reading up on checking the field resistances when I was looking into the powertronics unit. I'm not 100% sure how to do it thou. Everything refers to measuring resistance between different leads (Ie. Measure between E1, and E2 and not to go through the brushes). I'm not certain which wires/connections the E1 and E2 are. I'm sure there is more information somewhere on smokstak, I've just got to do some more searching.

I'm assuming the field resistance is the giant windings (armature) inside the actual generator, and you just measure the resistance from end to end. Short/Low Resistance = Bad, Open/High resistance = Bad, What should the resistance be?

V/R,
Justin
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  #35  
Old 09-15-2017, 06:46:50 AM
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Default Re: Onan JC Stumper

I do not have a Magneciter set, but I found some information on the resistance values. Page 56 of the 967-0500 manual states the rotor resistance should be 2 to 3 ohms. The C439 static exciter conversion instruction sheet specs the resistance to be 2.7 ohms. The resistance should be measured directly at the slip rings with the voltage regulator disconnected. The resistance of either slip ring to ground should be open.
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  #36  
Old 09-29-2017, 01:28:07 PM
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Default Re: Onan JC Stumper

I received the magnecitor from Max. (I can't thank him enough) Does anyone have a manual that includes all the testing / wiring of a magnecitor? I did some searches and any links I found all seem to be broken.

Since I'm going from the aftermarket voltage regulator, back to the original magnecitor. I want to make sure I wire\understand it correctly.

jmarrow@gmail.com

V/R,
Justin
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  #37  
Old 09-30-2017, 10:56:51 AM
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Default Re: Onan JC Stumper

Never mind, Just saw Max's PDF in a previous post. Thanks again Max
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  #38  
Old 09-30-2017, 02:36:33 PM
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Default Re: Onan JC Stumper

All right,

Field Resistance was 3.8ohm.

Wired it up, and I get an output of 248 volts. As I was checking things over with no load, monitoring temps for about 8 minutes with my laser temp gun. I noticed the black rod hit about 260 degrees F. So I shut the generator off. Is this normal or an indicator that something is still wrong?



V/R,
Justin
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  #39  
Old 10-04-2017, 05:00:26 PM
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Default Re: Onan JC Stumper

Sorry for the previous attempt at posting the image. The black vertical rod on the left. I don't know the official name of it. Ceramic Resistor?

I did order a different Tachometer. The type with the laser and reflective tape. The reading on the one I installed fluctuates 2-300 rpm even though the engine isn't. Needless to say it didn't give me confidence that it was accurate.

I'll re-verify the generator speed, and monitor.
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  #40  
Old 10-04-2017, 05:20:57 PM
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Default Re: Onan JC Stumper

You may or not already have one but the Killawat meter is what most guys use to check Hz or engine speed , they are quite cheap. Also the ceramic resistor does get somewhat hot, not sure how hot but they are big and ceramic for a reason. Cheers Dan
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