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003a unstable voltage

jamawieb

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Ok guys, I've got a 003a that I sold to a gentlemen. He brought it back because the 56ohm resistor on the rectifier board fried. So I replaced the resistor and got high voltage. I replaced the voltage regulator board with one of TripleJims, still high voltage. Found CVT1 was also bad, so I replaced that with a new one. Now I have unstable voltage, with everything set to 120/240 single phase, L3 jumps from 115-122 and L1 goes 90-140. All verified with 2 different multimeters. Checked the T2 transformer and it tested good.
 

jamawieb

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GuyFang, I checked the diodes per TM on A4 and they are good.

TripleJim it does cycle the same, ie going from 90 up to 130 then back down. It does not go 90 then 130 or anything like that.
 
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Guyfang

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I would think R1 could not have an influence like that. And you had too many parts damaged in the AC output box. If you had not changed the VR, I would have bet big money on it being just that. VR. It sounds like the set "thinks" is low voltage, and coraspondently corrects itself, then "sees" and over voltage, and ramps back down. How often between the voltage swings?

And the last post in the above mentioned link, indeed, the 400 hertz VR will work in a 60 hertz machine.
 

jamawieb

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I would think R1 could not have an influence like that. And you had too many parts damaged in the AC output box. If you had not changed the VR, I would have bet big money on it being just that. VR. It sounds like the set "thinks" is low voltage, and coraspondently corrects itself, then "sees" and over voltage, and ramps back down. How often between the voltage swings?

And the last post in the above mentioned link, indeed, the 400 hertz VR will work in a 60 hertz machine.
Its immediate swings back and forth.

The bad thing is, this unit went through a tier 2 reset in 2007 and has less than 200 hours. Ran perfect when I originally sold it to him. The guy let a family member use it and doesn't know what they did to it.
 

155mm

Chief and Indian
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So has throttle cable been checked to verify the lock/cable are servicable and mounted tight? Also is the return spring still on the IP where the throttle hooks up? After the electrics were repaired, it sounds like the throttle cable is stretched, or the lock isnt locking correctly.

Not even going to say that info was worth 2 cents, but I sure would check it. The reason I say check the cable, we had an old tractor that had a centrifugal governor and a throttle cable, with a light load the governor would surge just enough to be annoying, so took it to its name brand shop to get repaired, put a new governor on, brought it home, ran great for about an hour, then back to doing the same thing. Ended up being the 50 year old cable had stretched inside the sheath and had slack that let the throttle move 1/4" or less.
 

Triple Jim

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See if turning down the sensitivity pot helps. I labeled it "transient response" on the board, and it's the pot next to the voltage adjust pot. Normally you don't need to adjust that pot from where I set them during test, but your generator may have a little too much "uniqueness".

The second page of the instruction sheet explains how to make that adjustment, but turning it clockwise reduces the sensitivity and may help.
 
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Chainbreaker

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I put one of TripleJim's VR in the unit and have the problem. So I don't think its the pod on the VR.
I interpreted that post to be referring to the voltage adjust pot on "front panel", not the one on VR board itself. Meaning...does the front panel voltage adjust pot have any effect while the problem of unstable voltage is occurring. Although, perhaps I misunderstood "the clue" Jim was referring to in that thread I linked above (post #8 in this thread).
 
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Guyfang

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See if turning down the sensitivity pot helps. I labeled it "transient response" on the board, and it's the pot next to the voltage adjust pot. Normally you don't need to adjust that pot from where I set them during test, but your generator may have a little too much "uniqueness".

The second page of the instruction sheet explains how to make that adjustment, but turning it clockwise reduces the sensitivity and may help.
This has been on my mind, the whole time. A minor adjustment to the VR, because all sets are different, or, and I hesitated to bring this up, but, just because you put something new in, dosnt mean it works. A number of times in my life, I was troubleshooting problems and put in brand new, right out of the box, with QA/QC tags on it, parts. And they didnt work. After days of chasing my tail, I started all over again, and used completely different parts. And found I had put in one that didnt work. Just keep this in mind, if no other solution pops up. It could be the A4 card. The CVT1 or the VR.
 

Triple Jim

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That's why I asked if it was cyclic or random. Cyclic points toward an unstable control loop, so reducing the feedback constant by adjusting the pot could help. Random would make me look for a loose connection or bad solder joint somewhere.
 

GREENMV

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I am going to knock this one way out in left field. A couple years ago I had a 003a 10Kw that I started up to put it through it's paces to sell. I was testing power off the main lugs and it was fluctuating a lower voltage. I remembered when I first turned on the main breaker thinking it didn't snap on like they usually do, I turned off the main breaker and toggled it on and off a quite a few times to loosen it up after the generator sat for years. I turned the breaker on and after that and the voltage stayed steady. Something was just not contacting properly in the breaker and causing the voltage to be low and fluctuate. Easy fix that time. Another thought is something is just lose in the wiring and causing a bad connection.
 

frank8003

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Yeah Yeah
I opened a 30 amp breaker to part of the main AC.
Inspected everything, closed the breaker and it did zero, zip, was OK before I touched it.

On that Sunday I found a place open to sell me a breaker [yep, i did] and replaced the breaker.
All good after that.

I took the breaker to work -insert a lot of curse words here - and band-sawed it apart (not happy) and found when I had opened the breaker a spider walked onto the nice warm contacts to rest.
When I closed the breaker spider guts and all little gooey stuff fouled the contacts.
Spiders goo nasties give no continuity.
That was 65 bucks and three hours..............

After all these years I still hate that spider.
 

Chainbreaker

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Wow, and I thought spiders were considered to be a beneficial Arachnid because they trap and eat pesky insects. I guess I'm gonna have to put a "no Arachnid trespassing" sign on my generators now!
 
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