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Generator Won't Generate

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Mike Bell

Joined: 10 Jan 2006
Posts: 51

Posted: Mon Sep 04, 2006 6:45 pm Post subject: Generator Won't Generate

Test ran my Yak-52 after months of work only to find the "Generator Damage" light is on and ammeter confirms. Run-up to 70% doesn't make a difference. I have checked the overvoltage button (not popped), looked around in the "power supply" box (wiggled the fuses, and continuity confirmed on the big 30 amp fuses). I pulled the perfectly-running generator a few months ago to replace the brushes. Measured wrong and the old brushes were OK but since it was off  put in new ones. My recollection is that I ran it and the generator was fine but now I'm not positive about that. The 3 wires to the generator are in correctly. Lots of activity around the engine lately with new hoses and all, but no wiring touched. 



An old post mentioned the DMP-200D reverse current relay can fail, same with the voltage regulator or the TS-9M-2 transformer.



Surely there is a logical way to pin down the problem without replacing components one at a time.   Could the generator need the field flashed, or is that just urban legend? Appreciate any advice. Once this is fixed it will finally be flying again.

_________________
Mike Bell
Elk Grove, CA
avbell2(at)comcastdotnet

ggg6(at)att.net
Guest

Posted: Mon Sep 04, 2006 8:15 pm Post subject: Generator Won't Generate

Hi Mike, Gary Gabbard here, I have not had the problem on my CJ as I had an Alternator installed when when I put the M-14P in, but also have a 140 Cessna, the other day I started it and the Generator would not come on line, so shut down and flashed the field, started it up and the Generator came on line, no problem since... So it is not an Urban Legend..  Gary.   Good Luck.

 [quote]-------------- Original message from "Mike Bell" <yakflyr(at)comcast.net>: -------------- 

[quote] --> Yak-List message posted by: "Mike Bell" 

 

 Test ran my Yak-52 after months of work only to find the "Generator Damage" 

 light is on and ammeter confirms. Run-up to 70% doesn't make a difference. I 

 have checked the overvoltage button (not popped), looked around in the "power 

 supply" box (wiggled the fuses, and continuity confirmed on the big 30 amp 

 fuses). I pulled the perfectly-running generator a few months ago to replace the 

 brushes. Measured wrong and the old brushes were OK but since it was off put in 

 new ones. My recollection is that I ran it and the generator was fine but now 

 I'm not positive about that. The 3 wires to the generator are in correctly. Lots 

 of activ  ity ar  ronics  ibutio      [quote][b]

dsavarese(at)elmore.rr.co
Guest

Posted: Tue Sep 05, 2006 3:21 am Post subject: Generator Won't Generate

When you initially turn the battery switch on do you hear a "click" like 

relay contacts closing?

Dennis



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Rob Rowe

Joined: 10 Jan 2006
Posts: 124
Location: Berkshire, UK

Posted: Tue Sep 05, 2006 3:46 am Post subject: Re: Generator Won't Generate

Mike,



FWIW - couple of other quick checks;



- make sure the over-voltage protection relay АЗП-А2 has not tripped. Reset the external trip-button ... box just above your feet.



- be aware that if using external power the generator is forced offline until the powered external connector is removed (even when you've switched over to battery). Guess the tell-tale generator warning light helps prevent pilots aero-towing their GPUs 



Rob

wlannon(at)cablerocket.co
Guest

Posted: Tue Sep 05, 2006 8:43 am Post subject: Generator Won't Generate

No wive's tale. Residual magnetism is depleted over time if not in use. 

Flash the field.



Did you seat the new brushes? If not you may have some erratic operation 

initially. Brushes on these generators will last for many years.



Walt

---

mark.bitterlich(at)navy.m
Guest

Posted: Tue Sep 05, 2006 12:25 pm Post subject: Generator Won't Generate

Flashing a brand new generator is not urban legend as anyone who is old

enough to have driven a car with a real generator to can attest.

However... replacing the brushes would not result in a situation that

would require that.  Before looking into the reverse current relay,

voltage regulator, or anything else for that matter.. There are a few

things I would check first.  



First, (and this failure happened to me)...pull the engine through and

make sure the generator is actually turning.  No, I am not kidding.

The generator uses a drive shaft that is intended to shear under load

instead of transferring a jam up to the accessory drive system of the

engine, which could be catastrophic.  Since you recently had the

generator either out of the engine, OR just changed the brushes... It is

possible that something got screwed up somehow in that process and the

generator itself jammed.  If it did, you will have sheared the shaft and

you will be able to notice this either by pulling the generator and

turning it by hand or simply looking at it and seeing that it is not

turning at all with the engine either running or by pulling it through.

If that happened, buy a new generator.  You can usually get a used one

for $100 or less from someone who replaced it with a B&C system.  



If that is ok, and the generator is actually turning, start the engine

with the wire cover off the connections and check the output voltage of

the generator and the field winding, and report what voltages you get.

This will help narrow down what is happening.  



Good Luck, 



Mark Bitterlich 

N50YK



--

Mike Bell

Joined: 10 Jan 2006
Posts: 51

Posted: Tue Sep 05, 2006 1:14 pm Post subject: Re: Generator Won't Generate

Thank you all for the tips. There is a definite click when the batt switch comes on. I checked the overvoltage regulator red reset button and it's not tripped. I asked before on this forum about seating the brushes and was told not to worry about it. The Yak manual mentions a break-in procedure to be done on the bench but no specifics. If that's the problem it may cure itself. The generator is turning when I move the prop. I will check some voltages the next time I run it. 



Does anyone know how to flash the field on this specific generator? My IA is pulling out some old books to check on it. I have read all kinds of conflicting methods. My guess is disconnect the 3 wires from the generator so as not to fry anything else, then touch 24V positive from the battery to the field terminal (the little one in the middle). Some sources say to repeat it 5 times. hold it 30 seconds, brushes must be out, garlic around neck, etc.

_________________
Mike Bell
Elk Grove, CA
avbell2(at)comcastdotnet

wlannon(at)cablerocket.co
Guest

Posted: Tue Sep 05, 2006 1:32 pm Post subject: Generator Won't Generate

Mike;



Just remove the wire from the field terminal, find a source of 24v from the 

batt bus and contact the field terminal for 1 second. Brushes do not need to 

be removed.



You did say the generator has been idle for "months". That is a likely 

reason to lose the residual magnetic field.



Walt

---

rvfltd(at)televar.com
Guest

Posted: Tue Sep 05, 2006 2:02 pm Post subject: Generator Won't Generate

All smoke and mirrors, My CJ5 was in storage for 17 years, generator worked

perfectly when the engine was started.  Don't get me wrong, I'm not saying

that this is not the problem, only that I don't unnastan??  How many engines

have come out of 4-5 years of storage after overhaul and the gens are gening

just fine??



Always Yakin,

Doug Sapp



--

L39parts(at)hotmail.com
Guest

Posted: Tue Sep 05, 2006 2:36 pm Post subject: Generator Won't Generate

It depends on whether the plane was put in sorage pointed north or south.



---

wlannon(at)cablerocket.co
Guest

Posted: Tue Sep 05, 2006 2:44 pm Post subject: Generator Won't Generate

Very true Doug;



I have had the same experience but also a few that did not generate. Most of 

these were immediately "fixed" by flashing. This is over a 40 year period 

mostly with Bendix/Eclipse and Leece Neville generators all virtually 

identical to the Chinese (or Russian) variety.



There may be another problem but this is the first, and easiest, possible 

corrective action.



Cheers;

Walt



---

ggg6(at)att.net
Guest

Posted: Tue Sep 05, 2006 10:41 pm Post subject: Generator Won't Generate

Mike You can flash the field without removing the brushes, and it only takes a couple of times to apply voltage to the field, I never hold the hot wire on the field, only strike it for a second then off, it does not take much. Basically just arc the field terminal quickly...   Gary.. 

 [quote]-------------- Original message from "Mike Bell" <yakflyr(at)comcast.net>: -------------- 

[quote] --> Yak-List message posted by: "Mike Bell" 

 

 Thank you all for the tips. There is a definite click when the batt switch comes 

 on. I checked the overvoltage regulator red reset button and it's not tripped. I 

 asked before on this forum about seating the brushes and was told not to worry 

 about it. The Yak manual mentions a break-in procedure to be done on the bench 

 but no specifics. If that's the problem it may cure itself. The generator is 

 turning when I move the prop. I will check some voltages the next time I run it. 

 

 Does anyone know how to flash the field on this specific generator? My IA is 

 pulling out some old books to check on it. I have read all kinds of conflicting   

&  are, a       	  Quote: 	
		  [b]

Mike Bell

Joined: 10 Jan 2006
Posts: 51

Posted: Fri Sep 08, 2006 6:57 pm Post subject: Re: Generator Won't Generate

OK, we have ignition. After all sorts of poking, prodding, and research, walked into the hangar and looked at the generator and saw the problem right away. The new brushes have a bigger tab than the old ones, and a tab was rotated a hair and grounded on the frame of the generator. Fixed that and fixed the problem. Thought something was up after finding continuity between the armature and ground while the wires were disconnected. And I was all set to blame it on one of Doug Sapp's new hoses.

_________________
Mike Bell
Elk Grove, CA
avbell2(at)comcastdotnet

rvfltd(at)televar.com
Guest

Posted: Fri Sep 08, 2006 9:19 pm Post subject: Generator Won't Generate

Yep those generator hoses can be a bitch to get hooked up correctly.



Always Yakin,

Doug Sapp



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