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Additional Advice needed 7.5 JB YD generator end


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  #1  
Old 06-18-2014, 07:25:03 PM
wxyoung2008 wxyoung2008 is offline
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Default Additional Advice needed 7.5 JB YD generator end

A few weeks ago my brother, BidBud and I contacted this site because of an issue that we were having with a 7.5 JB 18r we recently acquired. It is producing only 48.5 volts per leg. We did all of the tests and finally sent the VR to Flight Systems. They did repairs and when it was returned and reinstalled still 48.5 volts.
A few measurements we did recently and today yielded these measurements:

TB21 terminal 1 and 2 yields 48vac
TB21 terminal 3 and 4 yields 0 volts when F1 & F2 are connected and 24vdc when F1 and F2 are disconnected.

Wires F1 and F2 are not grounded to each other.
Individual Fx wires are not grounded to the frame.

We have tested CR1-6 and they test correctly both forwards and backwards.

Something within the generator seems to be holding down the VR control voltage when F1 and F2 are connected.

At this point am I probably looking at an open or short within the gen end ?
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Old 06-18-2014, 08:59:59 PM
Jim Rankin Jim Rankin is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

Quote:
Originally Posted by wxyoung2008 View Post
TB21 terminal 1 and 2 yields 48vac
TB21 terminal 3 and 4 yields 0 volts when F1 & F2 are connected and 24vdc when F1 and F2 are disconnected.

Wires F1 and F2 are not grounded to each other.
Individual Fx wires are not grounded to the frame.

We have tested CR1-6 and they test correctly both forwards and backwards.

Something within the generator seems to be holding down the VR control voltage when F1 and F2 are connected.

At this point am I probably looking at an open or short within the gen end ?
When you say F1 and F2 are not grounded to each other, do you mean there is no resistance shown on the meter when you test from F1 to F2 with them disconnected from the TB 21? (this is an indication that your exciter field winding is open, but does not explain why connecting F1 and F2 to TB21 would eliminate 24 volts output from the VR).

F1 and F2 not being "grounded" to the frame is good, but again, not sure why connecting them up to the VR would eliminate the voltage output.

As a test of the integrity of the whole generator end (less the regulator), apply 12 volts to F1 and F2 with the generator running normal speed and report back what voltage output you get.
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  #3  
Old 06-18-2014, 09:41:19 PM
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Default Re: Additional Advice needed 7.5 JB YD generator end

Maybe the moderator can merge these two threads together as it is a PITA to figure out what's transpired...

Other thread:

http://www.smokstak.com/forum/showthread.php?t=134143

Wierd symptoms for sure...


I'd advise caution with the 12V test that Jim R suggested. It works if you know what you are doing. BUT you DO NOT want to feed 12V into the output of the V/R, so it must be disconnected. If this makes no sense, don't proceed.

As an alternate quick test, try flipping the F1 and F2 wires.



Any history on this set? Or is it new-to-you?

Last edited by Jim McIntyre; 06-18-2014 at 10:01:31 PM.
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Old 06-18-2014, 10:18:13 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

Quote:
Originally Posted by Jim McIntyre View Post
Maybe the moderator can merge these two threads together as it is a PITA to figure out what's transpired...

Other thread:

http://www.smokstak.com/forum/showthread.php?t=134143

Wierd symptoms for sure...


I'd advise caution with the 12V test that Jim R suggested. It works if you know what you are doing. BUT you DO NOT want to feed 12V into the output of the V/R, so it must be disconnected. If this makes no sense, don't proceed.

As an alternate quick test, try flipping the F1 and F2 wires.



Any history on this set? Or is it new-to-you?
I believe that I can safely get 12v to the input of the generator safely by disconnecting the VR pretty much all together. What would this test prove .... That the VR is still bad or ??????. Thanks

I will also try flipping the two wires. No history except I bought it off a CL seller who claims to have bought it from the original owners widow.

---------- Post added at 09:13 PM ---------- Previous post was at 09:08 PM ----------

Quote:
Originally Posted by Jim Rankin View Post
When you say F1 and F2 are not grounded to each other, do you mean there is no resistance shown on the meter when you test from F1 to F2 with them disconnected from the TB 21? (this is an indication that your exciter field winding is open, but does not explain why connecting F1 and F2 to TB21 would eliminate 24 volts output from the VR).

F1 and F2 not being "grounded" to the frame is good, but again, not sure why connecting them up to the VR would eliminate the voltage output.

As a test of the integrity of the whole generator end (less the regulator), apply 12 volts to F1 and F2 with the generator running normal speed and report back what voltage output you get.
Jim
The resistance between F1 and F2 is 18.5 ohms. That is measured end to en F1 to F2 disconnected from TB21.

---------- Post added at 09:18 PM ---------- Previous post was at 09:13 PM ----------

Also , I am using a Kill-a -watt meter plugged into an outlet I connected to one of the legs to and set the gen to 61.5 hz. It is exactly the same voltage on either leg.
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  #5  
Old 06-18-2014, 10:52:19 PM
Isaac-1 Isaac-1 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

When you feed 12V (feed through a small fuse if using a car battery for safety) to F1 and F2 as mentioned above with the AVR disconnected what does the output voltage do? Also i see from the other message thread that this generator is missing its tags, is it a 4 lead or a 12 lead set? If 12 lead is it connected correctly?

Ike

p.s. also as much as I like the kill-a-watt it is a cheap meter, have you confirmed the voltage readings with another known good meter?
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Old 06-18-2014, 10:55:15 PM
AndersonMillTexas AndersonMillTexas is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

What would make the resistance increase? I am learning here to. It would seem that the resistance would go down if the winding varnish is wearing out?

Did you disconnect F1 and F2 from the cr's before testing? I forgot on my first hasty attempt. I also forgot to disconnect the battery.

My reading was high but after cleaning the contact the resistance went to normal.
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Old 06-18-2014, 11:06:56 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

Quote:
Originally Posted by Isaac-1 View Post
When you feed 12V (feed through a small fuse if using a car battery for safety) to F1 and F2 as mentioned above with the AVR disconnected what does the output voltage do? Also i see from the other message thread that this generator is missing its tags, is it a 4 lead or a 12 lead set? If 12 lead is it connected correctly?

Ike

p.s. also as much as I like the kill-a-watt it is a cheap meter, have you confirmed the voltage readings with another known good meter?
I did not see the other thread but mine is NOT missing its tag. It is a 7.5 JB 18r 12 leads . I have poured over the wiring many times and I believe it to be wired properly. I have used a volt meter and a 120v house lamp reveals that I an in no wise getting 120 volts.
And thanks .... I will fuse it and probably run out and get a lantern battery as I need one anyway

---------- Post added at 10:02 PM ---------- Previous post was at 10:00 PM ----------

We do also have a 6.0 DJB but it is fine and currently undergoing a paint job.

---------- Post added at 10:06 PM ---------- Previous post was at 10:02 PM ----------

Quote:
Originally Posted by AndersonMillTexas View Post
What would make the resistance increase? I am learning here to. It would seem that the resistance would go down if the winding varnish is wearing out?

Did you disconnect F1 and F2 from the cr's before testing? I forgot on my first hasty attempt. I also forgot to disconnect the battery.

My reading was high but after cleaning the contact the resistance went to normal.

I did not Anderson when I tested F1 to F2 just did an end- to- end test
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Old 06-18-2014, 11:15:43 PM
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Default Re: Additional Advice needed 7.5 JB YD generator end

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Originally Posted by wxyoung2008 View Post
...I have poured over the wiring many times and I believe it to be wired properly...
If you have ANY doubt, you could disconnect all 12 wires, leaving them to float in the air, taping them up if necessary, and again check the TB21 terminal 1 and 2 voltage.
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Old 06-18-2014, 11:15:59 PM
Kimbra Dean Kimbra Dean is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

Does the voltage at 1 and 2 change when F1 and F2 are connected/disconnected?
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Old 06-18-2014, 11:17:44 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

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Does the voltage at 1 and 2 change when F1 and F2 are connected/disconnected?

It does not change . Stays at 48 vac
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Old 06-18-2014, 11:18:07 PM
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Default Re: Additional Advice needed 7.5 JB YD generator end

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Originally Posted by Kimbra Dean View Post
Does the voltage at 1 and 2 change when F1 and F2 are connected/disconnected?
Hmm. Good question!
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Old 06-18-2014, 11:24:11 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

No it does not change. Looks like the only voltage that I am seeing is the same TB21 1 and 2 residual.
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Old 06-19-2014, 05:01:42 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

So today guys I went out and found a 6 volt lantern battery to use to apply some dc to F1 and F2 using the inputs of where they would attach to the VR board. I removed the VR board entirely. Fired it up and it measured 122 vac.
Plugged in a lamp and it worked perfectly. I was glad to see that. Hopefully that is telling me that my gen end is probably ok.

So here is my dilemma:

Does it appear that I still have an issue with the VR board that I sent out for repairs a week ago ?

Also as a side note to the operation that I just performed , I lost my residual field voltage. Pin 1 and pin 2 residual voltage went to .2 ( down from 48) and I am assuming that the field will need to be flashed. Could that have been caused by my running the generator with the VR totally removed ?

Thanks
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Old 06-19-2014, 06:03:04 PM
Wayne 440 Wayne 440 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

The YD end has a small magnet in the exciter portion of the rotor. I think your 6V battery probably created a "backwards" field voltage so that now the residual in the iron and that of the magnet are opposite. Fire it up and hook the lantern battery up the other way for a few minutes.

Then try your VR with F1 and F2 reversed from the way it was when you started. Can you try the VR out of the DJB in it?
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Old 06-19-2014, 07:30:38 PM
wxyoung2008 wxyoung2008 is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

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The YD end has a small magnet in the exciter portion of the rotor. I think your 6V battery probably created a "backwards" field voltage so that now the residual in the iron and that of the magnet are opposite. Fire it up and hook the lantern battery up the other way for a few minutes.

Then try your VR with F1 and F2 reversed from the way it was when you started. Can you try the VR out of the DJB in it?
I will try that with the battery tomorrow. I don't think I can use the VR out of my DJB because it is a different type and is huge. But I never checked the connections on the back so it might hook up just the same. I will at least look tomorrow.
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Old 06-19-2014, 09:39:31 PM
AndersonMillTexas AndersonMillTexas is offline
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Default Re: Additional Advice needed 7.5 JB YD generator end

I have been following this thread and am a bit confused.

I was under the impression that the Voltage regulator samples voltage and then sends a DC voltage between 1 and 12 volts to the Exciter to manipulate the final out put.

#1. Why would only 6 volts give him 122 volts and not 12?

#2. Could he not measure the out put of the VR and assuming he gets 48 volts from the gen then we could expect about 2 volts out put from the VR?
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Old 06-19-2014, 10:19:41 PM
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Default Re: Additional Advice needed 7.5 JB YD generator end

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I have been following this thread and am a bit confused.
PM sent so we don't derail the thread.
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