003a unstable voltage

[jamawieb]

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.

Alright Jim, It looks like R11 resistor on the VR board has failed. I've been slowing testing everything and I'm back at the VR. Could the bad CVT1 have caused the failure? looks like R11 is in conjunction with T2 transformer.

 

[Triple Jim]

It's T1 that supplies power through CR8 CR9 and CR10 to that resistor. If something caused the 18v zener diode CR6 to fail shorted, R11 could overheat. I suppose that if the control winding in CVT1 shorted to another winding, it could have put current into that control loop and caused the problem.

If you send the regulator I built back to me, I'll fix it for you.

 

[155mm]

If you send the regulator I built back to me, I'll fix it for you.

thats what i call service with a smile

 

[jamawieb]

It's T1 that supplies power through CR8 CR9 and CR10 to that resistor. If something caused the 18v zener diode CR6 to fail shorted, R11 could overheat. I suppose that if the control winding in CVT1 shorted to another winding, it could have put current into that control loop and caused the problem.

If you send the regulator I built back to me, I'll fix it for you.

Jim,
I sent you an email to stockbox@lakeserv.net. Thank you for taking the time to look at the VR and of course would pay for your time and materials to fix it. Thanks for the great service!

 

[Triple Jim]

Jimmy, no need to pay since it's guaranteed for at least two years. I don't argue about what caused the failure, and I may make changes to prevent future damage from a failed CVT1 based on your experience, so it'll help both of us.

 

[jamawieb]

Update: So I sent the VR back to Jim, he received it Friday and reported the resistor that I thought failed was good but went ahead and replaced it. Had it back in the mail the same day!!! You can't beat the service TripleJim has on the VR's, this includes DC regulators. So today, I took my VR out of my personal unit and had the same fluctuations. So I started over again, after tracing wires all day, I finally found a bad connection at TB3 terminal 6. After I fixed the connection, the generator is working perfect. Load tested at 14kw for 2 hours and no problems. Thanks everyone for the help.

 

[Guyfang]

Some of these gen sets are older then most members of SS. Unless you loosen and thighten each and every nut, screw and bolt, check each and every electrical connection on your set, this will happen. Good job finding it, as this kind of failure is without a doubt, the most frustrating fault to find!! Again, good job.

 

[Triple Jim]

I was glad to hear the success story. The resistor, R11, was definitely overheated and badly discolored, so it needed replacement. I just checked its resistance for fun once I got it out of the board, and it was within an ohm or two of its 330 ohm nominal value. That's a tribute to modern metal film resistors!