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Onan 7.5JB - Wiring


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  #21  
Old 01-29-2017, 08:11:33 PM
Ray Lynch Ray Lynch is offline
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Default Re: Onan 7.5JB - Wiring

Kiteoregon
Do you have the JB manual for your set? From your posts, it seems you would benefit from reading it thru to get info such as setting the governor, etc that you need. It will help you understand better the overall operation of your set.
Check your meter against a known 230 volt source and if ok re-check the readings on your set.
Ray
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  #22  
Old 01-29-2017, 09:29:27 PM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

So i verified that my MM is not moving a decimal point. So i have it connected to L1 and only able to get 2.20 - 2.40 volts. I would expect that L1 with my configuration should be putting out close to 110v. Additional ideas?

---------- Post added at 05:14:52 PM ---------- Previous post was at 05:04:51 PM ----------

I read through the service manual, the screw that i was adjusting was the governor screw. How far up is it safe to turn? As i turn the screw the RPMs go up as does the voltage, but i am just not sure how far it should go. Seems like a long jump 2.40 to 110?

---------- Post added at 05:29:27 PM ---------- Previous post was at 05:14:52 PM ----------

I started the gen and let it warm up, then twisted the governor screw to max, at max i was getting 5.xx volts. Seems like there is something else, i am off by a significant magnitude.
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  #23  
Old 01-29-2017, 10:30:49 PM
Augie1 Augie1 is offline
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Default Re: Onan 7.5JB - Wiring

It is on the front of the
generator upper left side of the flywheel. I wouldn't mess with it just yet. It will be one more thing to get adjusted later. Do some more reading on this site about adjustments or in your manual. Have you looked inside the control box for a mouse nest? Have you checked out your voltage regulator board .

---------- Post added at 08:06:59 PM ---------- Previous post was at 07:59:24 PM ----------

If you turned the gov adjust to max you will be running well, well over the rated 1800 RPM. You don't want to ruin a good engine. Check all fuses and the VR board.

---------- Post added at 08:17:51 PM ---------- Previous post was at 08:06:59 PM ----------

Check out this thread by Jim on how To: Quick Test for the JB JC YD Voltage Regulator.

---------- Post added at 08:30:49 PM ---------- Previous post was at 08:17:51 PM ----------

https://www.smokstak.com/forum/showthread.php?t=146239
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  #24  
Old 01-30-2017, 08:14:52 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5JB - Wiring

As mentioned above, you will not get from 3 volts to 240 with engine speed. You need to do some reading of the YD generator manual.

How long had it been since the generator was producing power. Built in 1996, you will have a voltage regulator board that may be the problem, or the gen-end may need to be flashed.

If you do not have the generator output wires configured correctly, you will not get proper voltage & may smoke something. Double check this configuration FIRST.
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Old 01-30-2017, 12:09:49 PM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

I will pick up the parts today to make a test light and test the voltage regulator per the post / link above and report back.

I would expect that since i am only testing voltage on L1, i should expect to see 110, correct? Then once i get 110 on L1, check L2, i should also get 110 there. But first, will test the penthouse electronics.

Last run is unknown. The generator odometer has 115 hours, don't know much more of then history then that. The points were in very bad shape and took some time to clean just to get started, so it's probably been several years at a minimum. PO told me that it operated fine, just ran out of propane one day and so he disconnected the wiring and connect to a portable, then just never hooked it back up to the house.

Thanks.
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  #26  
Old 01-30-2017, 04:17:11 PM
Radarman Radarman is offline
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Default Re: Onan 7.5JB - Wiring

KiteOregon, I am just down the road from you in Beaverton. Im no expert, but if you need a second set of eyes and/or tools, let me know. I just finished going through a JB last year so its not my first rodeo..

As far as why your voltage is reading low, as mentioned before it is most likely NOT related to RPM, but due to your voltage regulator, wiring or something like that.
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Old 01-30-2017, 04:34:16 PM
len k len k is offline
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Default Re: Onan 7.5JB - Wiring

Might be easier to do a functional test on gen head (windings and rectifier diode)....
I don't know 3 phase units that well , but on my single phase JB with YD reg (electronic one) the field that reg feeds is ~ 12 ohms. If I disconnect the reg and apply 12 VDC to the field I get 140 VAC output out the 120 leads on mine. Polarity does matter, there is supposed to be a small flashing permanent magnet in the field that gives ~ 15-20 VAC output with NO reg connected.

To determine correct polarity on mine:
-- I disconnected the reg , ran gen and measured output voltage.
-- Then applied one alkaline 1.5 V D dry cell (flashlight bat) to the field , ran engine and measured output voltage.
-- Then reverse cell connections to field and repeated above.

The correct polarity is that which results in a higher output voltage.( the fields from magnet and electromagnet combine). If you have reg output connected in reverse I theorize output voltage that powers the reg will go near zero as it trys to bootstrap itself and reg will stall out from lack of voltage.

Last edited by len k; 01-30-2017 at 11:00:38 PM.
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Old 01-30-2017, 06:10:15 PM
squidtrap squidtrap is offline
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Default Re: Onan 7.5JB - Wiring

First thing i recommend is read the owners manual and operators manual that they sent, also buy a kill-a-watt meter for 20.00 (best 20 u will spend owning a generator) this way you get familiar with the gen, and will have the meter so when making adjustments you will see what is doing what.

You will be surprised how easy they are to work on once you get familiar with what does what. one wrong move and you could let out the magic smoke, and you do not want to do that.

Trust me that paperwork is your best friend, next to the experts here that will be guiding you through some of the issues you may come across, good luck, Ed.
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  #29  
Old 01-30-2017, 10:38:44 PM
len k len k is offline
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Default Re: Onan 7.5JB - Wiring

Make sure your voltmeter is connected between the L1, L2, L0 connections and not between L1 , L2 and frame.
Because if you haven't made a connection between your neutral and the frame, then only stray capacitance will complete the voltmeter circuit and meter will read low.

Also if meter is bad/intermittent , could try a good light bulb between L1 and L0 ....... and between L2 and L0. See if it lights.

Sounds like your gen is wired in 120/240 double delta mode, the neutral L0 is typically the lead group T2, T4, T7, T12. and is connected to frame ( ground) for typical USA 120/240 single phase home utility power.

Last edited by len k; 01-30-2017 at 11:12:13 PM.
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  #30  
Old 01-31-2017, 12:52:37 AM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

Per Jim's post i removed the penthouse and tested with a 60w incandescent light bulb. After some pot adjustments the light bulb will come to full brightness. So at this point we can rule out the voltage regulator and transformers located in the penthouse.

I did find lots of mouse mess inside the electrical box under the penthouse however and cleaned that all up. The rest of the wires and housings in the box seem to be in good shape.

I am guessing now start to look at the generation side of things?

---------- Post added at 08:52:37 PM ---------- Previous post was at 08:51:04 PM ----------

Len, just saw your post, i will test with a light to verify it's not my cheap MM.
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  #31  
Old 01-31-2017, 01:00:28 AM
len k len k is offline
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Default Re: Onan 7.5JB - Wiring

If low voltage is real , my next guess is rotating diodes are blown.
Disconnect reg and run engine, my JB spec AA makes ~ 15-20 VAC out the 120 leads under these conditions, it's field has a small permanent magnet built in.

Basically the reg powers a field stator, it's rotor makes 3 phase AC that is rectified to DC by 6 diodes to power 2nd stage rotor that makes AC into 2-nd stationary stator. I think the magnet is in the feild of the 1-st stator.

My Onan 7NHM makes 1-2 VAC when reg is disconnected, it doesn't have a small permanent magnet.
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  #32  
Old 01-31-2017, 01:32:39 AM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

With the voltage reg assembly removed and the volt meter connected to the wires that connect to TB21-1 and TB21-2, i read 2.6 volts ac while running.

Based on the service manual, it would seem my next logical step is to flash the field, but since i don't have a 6 volt battery, i will pick a 20 ohm resister and wire in series per the manual and flash the field to see if restoring magnetism will result in output voltage.
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  #33  
Old 01-31-2017, 01:49:40 AM
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Default Re: Onan 7.5JB - Wiring

You can try flashing the field but it is not likely to do anything. The next logical step is to test the resistance of the field across F1 and F2. You should get 12 Ohms or so. The exciter coil ( field ) is the next most common failure point in a YD genend then the rotating diodes as Len has suggested. If the exciter coil measures around 12 ohms you can try putting 12V across it while running, this should give you over 100V output. Get back to us with the results. Cheers Dan
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  #34  
Old 01-31-2017, 01:59:40 AM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

With the set NOT running, MM connected to F1 and F2 i get 11.6 ohms. Once started i get 0 ohms.

]Just so i understand, now that i see roughly 12 ohms, i should start the generator and apply 12V to the F1 and F2. Is this with the voltage regulator disconnected? Do i measure output voltage on F1 & F2?
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  #35  
Old 01-31-2017, 02:04:47 AM
len k len k is offline
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Default Re: Onan 7.5JB - Wiring

On my single phase JB , 12 VDC ( car bat) across field yielded ~140 VAC out the 120 lines. Suspect your 3 phase will do ~ same.

Kiteorgan....just saw your post

11.6 ohms sounds close enough to call it good, even if couple of the ~ 10 coils were shorted I would think the 1-st stage should make enough excitation so 2nd stage should make something like 70-90% of 120 VAC .

With gen rotating ohming field is meaning less, voltage from residual magnatizm makes ohmmeter give false readings.
Need gen stopped to obtain valid ohm readings.

You apply 12VDC across F1/F2 with reg disconnected, run gen and see what you get out the 120 leads ( L1 to L0) and (L2 to L0). Looks like positive of 12V bat should be connected to F1. Negative to F2

But first, With reg disconnected, engine off, measure resistance from either F1/F2 to frame. Should be >~ 1,000,000 ohm (insulation test)

Last edited by len k; 01-31-2017 at 12:10:57 PM.
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  #36  
Old 01-31-2017, 03:14:24 AM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

Check on the insulation test, north of 10.78 m ohm.

Will apply 12v and check leads as you suggested.

---------- Post added at 11:14:24 PM ---------- Previous post was at 10:54:22 PM ----------

Ok, so applied the 12V+ to the F1 wire and 12V- to the F2 wire. MM connected to L1 and L0. Started the set, output voltage 48.4 - 48.8 ish. It seemed that when the 12v was applied the generator seemed to be under load, once removed it was like the load was removed. Voltage Reg has been disconnected through all of this.
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  #37  
Old 01-31-2017, 07:39:13 AM
b74eqcm b74eqcm is offline
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Default Re: Onan 7.5JB - Wiring

Quote:
Originally Posted by kiteoregon View Post
]Ok, so applied the 12V+ to the F1 wire and 12V- to the F2 wire. MM connected to L1 and L0. Started the set, output voltage 48.4 - 48.8 ish. It seemed that when the 12v was applied the generator seemed to be under load, once removed it was like the load was removed. Voltage Reg has been disconnected through all of this.
OK, so this sounds like a short. I suspect you don't have the output leads connected correctly, and have at least one phase in a bolted short. Double and triple check your output leads before doing anything else, as this could cause serious damage. If you are absolutely sure they are right, it's time to check the stator windings to find the short.
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Old 01-31-2017, 08:00:05 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5JB - Wiring

Quote:
Originally Posted by kiteoregon View Post
Per Jim's post i removed the penthouse and tested with a 60w incandescent light bulb. After some pot adjustments the light bulb will come to full brightness. So at this point we can rule out the voltage regulator and transformers located in the penthouse.
Where was the bulb connected & what was the voltage present at those connections when the bulb came to "full brightness".
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  #39  
Old 01-31-2017, 09:16:48 AM
Kevin K Kevin K is offline
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Default Re: Onan 7.5JB - Wiring

You might want to try disconnecting all 12 output leads, let them float, and run the test again applying 12 volts to F1 & F2. If the engine loads up when 12 volts is applied, you probably have a short somewhere. If it passes this test, check each lead for short to ground. If that is OK, you probably had a bolted short as b74ecqm suggested.
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Old 01-31-2017, 12:00:46 PM
kiteoregon kiteoregon is offline
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Default Re: Onan 7.5JB - Wiring

The bulb was connected to F1 and F2, i did not check the voltage at that point, but will later today. In the pic, the red wires are for the light, the white is the 110 source. I will hook this back up after work and check the output voltage where the light connects.
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