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GP9 Not loading

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GP9 Not loading
Posted by Benlegault on Thursday, October 19, 2023 3:12 PM

We have a basterdized GP9 that has had heavy mods done to it. upgraded contactors and electrical equipment. We had issues with throttle position 5 to 8 having no change in engine RPM. Which led us to think that the governer was the problem after we checked the throttle drum switches. Engine ran good for one night after the governer switch (keep in mind the governer was used from another company we had one on order) and came back with loading issues. Will not load. RPM goes up normally and the load regulator goes to max on throttle position 1. Any ideas would be helpful. We also get a low voltage ground fault when starting. The conductors say it's been like that for years so I'm not too worried about that being an issue. I am I wrong to think that the load regulator shouldn't be going to max in position 1?

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Posted by Overmod on Friday, October 20, 2023 3:58 AM

Benlegault
We have a bastardized GP9 that has had heavy mods done to it. upgraded contactors and electrical equipment. We had issues with throttle position 5 to 8 having no change in engine RPM. Which led us to think that the governer was the problem after we checked the throttle drum switches. Engine ran good for one night after the governer switch (keep in mind the governer was used from another company we had one on order) and came back with loading issues. Will not load. RPM goes up normally and the load regulator goes to max on throttle position 1. Any ideas would be helpful. We also get a low voltage ground fault when starting. The conductors say it's been like that for years so I'm not too worried about that being an issue. I am I wrong to think that the load regulator shouldn't be going to max in position 1?

First, you have an issue perhaps not with the governor internals but with how the 'notch' solenoid system is modulating the governor.  I am by no means an expert on this, but understanding the system will tell you if one or more solenoids are bad or miswired.

Each 'notch' is supposed to represent a governed engine speed, which the hydraulics of the Woodward governor then 'holds' within a few rpm.  The governor completely handles the engine load via the fuel rack, feeding more or less fuel to keep the engine on constant rpm as it loads down.  This is not a 'speed control' and it's automatic within the practical range of the engine governor.

The automatic load regulator is adjusting the electrical load on the engine separately (so the engine does not bog down or be incorrectly loaded during operation).  It can do this very quickly, compared to what would be required by something like a FADEC constantly tweaking engine rpm up or down, but in my opinion you should see it modulate even at low speed, not go straight to full and stick there.

My two cents is that you should pose these questions, with pictures, over on RyPN (where there are a number of people who have hands-on experience and extensive knowledge both of GP7s/9s and how they come to be kludged).

(This isn't by any chance the locomotive that was built with a 567C block and now has a BC engine, is it?)

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Posted by Randy Stahl on Saturday, October 21, 2023 4:21 PM

Benlegault

We have a basterdized GP9 that has had heavy mods done to it. upgraded contactors and electrical equipment. We had issues with throttle position 5 to 8 having no change in engine RPM. Which led us to think that the governer was the problem after we checked the throttle drum switches. Engine ran good for one night after the governer switch (keep in mind the governer was used from another company we had one on order) and came back with loading issues. Will not load. RPM goes up normally and the load regulator goes to max on throttle position 1. Any ideas would be helpful. We also get a low voltage ground fault when starting. The conductors say it's been like that for years so I'm not too worried about that being an issue. I am I wrong to think that the load regulator shouldn't be going to max in position 1?

 

Notch 5-8 is the D soleniod, focus there, if the load reg is not moving off of max field check the generator shunt field. 

 

R Stahl

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Posted by Overmod on Saturday, October 21, 2023 7:07 PM

Welcome back, Randy!

To the OP: Randy Stahl is experienced in this field.  Pity the PM function here won't let you contact him directly... but I'll be interested to see how this thread helps you find and correct the problems.

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Posted by daveklepper on Sunday, October 22, 2023 2:06 AM

1,   Do you have the GM-EMD manuel for the GP9?

If  I recall, the control circuits used resistors as volytage dividers.  You might want to check the actual restance, as measured with an Ohm-Meter, against the color-code label.   One of the resistors may have failed.

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Posted by daveklepper on Sunday, October 22, 2023 2:11 AM

Incidently, at age  91+, away from any electronic designs desk for 26 years, can some reader please refresh my memory on the rssistor resistance color-code?

 

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Posted by Overmod on Sunday, October 22, 2023 11:54 AM

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Posted by daveklepper on Monday, October 23, 2023 10:54 AM

THANKS!   Todah  Shukhran

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Posted by Erik_Mag on Tuesday, October 24, 2023 12:01 AM

What scares me is that my first exposure to the color code was in the beginning of a junior high electronics shop class 55 years ago. Back then it wasn't uncommon to see resistors without any tolerance band, i.e. the mfr couldn't evenguarantee +/-10% - whereas now 1% is usually the loosest tolerance. Other thing that's disconcerting is that in 1968, the 6L6 was only a 30 year old design, whereas there are still a few IC's from that time that are still in production.

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Posted by daveklepper on Thursday, October 26, 2023 5:50 AM

Old IC designs?   "If it ain't broke don't fix it."

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Posted by daveklepper on Thursday, October 26, 2023 6:02 AM

There is a land-mark 52-year-old sound system in an important church that was the pioneer in a specific application of digital audio processing.  The digital equipment and the power amplifiers were replaced by more modern equipment about 20 years  ago by a sound-system contractor who retained friendship with me after my moving to Jerusalem 26-1/2 years ago.  He now reported that another contractor, one better-known for theater sound systems, replaced some loudspeakers that finally had suspensions that became brittle, and also replaced the power amplifiers, the second  time for this.  The problem in the power amplifiers was simply dirt in the volume controls which could easily have been cleaned.  But the new contractor did not know this and caused  additional expense for the  church.

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Posted by rdamon on Thursday, October 26, 2023 7:28 AM

Erik_Mag

What scares me is that my first exposure to the color code was in the beginning of a junior high electronics shop class 55 years ago. Back then it wasn't uncommon to see resistors without any tolerance band, i.e. the mfr couldn't evenguarantee +/-10% - whereas now 1% is usually the loosest tolerance. 

 

I can still hear my shop teacher's politically incorrect mnemonic to remember the color order 40+ years later.

The world's problems could be solved with a LM741!!  Big Smile

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Posted by Overmod on Thursday, October 26, 2023 9:52 AM

Is that the one where Violet gives willingly?

At the Englewood School for Boys we learned it as "Better be right or your Great Big Venture goes west!"

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Posted by rdamon on Thursday, October 26, 2023 12:17 PM

Overmod

Is that the one where Violet gives willingly?

 

Suzy Gives None

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Posted by Overmod on Thursday, October 26, 2023 1:08 PM

rdamon
Overmod

Is that the one where Violet gives willingly?

Suzy Gives None

And here I was thinking that tolerance was one of her main qualities...

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