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Generac Generators (SEARS, etc.)

Voltage Regulator for MC-40 Generac


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  #1  
Old 05-20-2010, 04:41:55 PM
golddredger golddredger is offline
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Default Voltage Regulator for MC-40 Generac

Ok, here's the problem...I've got a 1978 generac 4kw generator, mod # 6897-3, has a bad voltage regulator I believe....found the diagnostic and repair manual online, went thru the genny, I'm getting 150 volts at the terminals out of the generator....reset the governor, carb, etc; checked exciter, field, stator, rotor, diodes, breakers, etc and everything checks within specs...only thing left is the regulator.... called repair shop in ocala, fl and they said generac doesnt make that part anymore, wanted to sell me a new one....well, at the moment I'm stripping the epoxy off the old reg, have the back of the board cleared, and can see all the parts on the front....will have a layout and parts list soon for all you people like me, too much time and not enough money on our hands.... if anyone can help me find a regulator, that would be so much easier, unless the price is outrageous....

1978 generac mc-40
mod # 6897-3
120 v 33.3 a
3600 rpm
single phase
ser # 0567450
4000 w


thanx.....
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  #2  
Old 05-20-2010, 04:45:37 PM
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BTPost BTPost is offline
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Talking Re: voltage regulator for mc-40 generac

What is the NUMBER on the Voltage Regulator Board?
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Bruce in alaska
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Old 05-20-2010, 10:14:38 PM
K D Redd K D Redd is offline
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Default Re: voltage regulator for mc-40 generac

Can you post a picture of the board? I repaired a friend's 10 year newer 4 KW generator by repairing the board. On it, the only thing on the board was a bridge rectifier that was bad. If you will look down this page for my post Older 4k Generac you will find picture of the board. I do not know if it is similar to yours. The Generac dealer wanted $ 75.00 for the board. I fixed it for $ 4.00.

Kent
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Old 05-21-2010, 08:35:43 AM
Warren914 Warren914 is offline
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Default Re: Voltage Regulator for MC-40 Generac

A heat gun works well on the epoxy. It becomes brittle and chips off quite easily.
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Old 05-21-2010, 08:27:15 PM
golddredger golddredger is offline
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Default Re: voltage regulator for mc-40 generac

the number on the back of the case is 614h....the number on the back of the circuit board is generac 42323r2.....took some pics of the board and case....will see if i can load them on here
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Old 05-21-2010, 08:32:50 PM
golddredger golddredger is offline
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Default Re: voltage regulator for mc-40 generac

took some pics of the board and case, will see if i can load them on here....
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Old 01-17-2011, 05:04:34 PM
vmax85 vmax85 is offline
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Default Re: Voltage Regulator for MC-40 Generac

try this http://www.flightsystems.com/Generac...g_services.htm
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Old 01-19-2011, 10:55:40 PM
jimgrease jimgrease is offline
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Default Re: Voltage Regulator for MC-40 Generac

Hey, didn't I post a few replies to this thread last year? You know, all that work I did to draw up the schematic of this regulator circuit since I have the same board in my old JC Penny Generac?

Strange

Last edited by BTPost; 01-19-2011 at 11:03:55 PM. Reason: LOOK at the TOP of the Forum List..... BTPost
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Old 01-20-2011, 01:00:16 AM
jimgrease jimgrease is offline
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Default Re: Voltage Regulator for MC-40 Generac

BT,

Ha, I finally found them.

Well, even with that hint, it still took me awhile to figure out what you did with the missing posts.

I'm glad you found my contribution worthy, thanks.

I've been distracted by more pressing needs since I first replied here; and I still have to put the finishing touches on my generator restoration. But I do check out this thread on occasion and was obviously surprised to see the change.

It was my original plan to modify the voltage regulator board and include some extra safety features that my cheap Generac lacks. I will promise to post back again once I've completed that task.

Hopefully Golddredger eventually figured out his problem.........or at least got a working generator.
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Old 01-20-2011, 09:17:32 AM
Kevin K Kevin K is offline
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Default Re: Voltage Regulator for MC-40 Generac

Jimgrease,

I want to thank you for taking the time to trace this circuit out and post it. With a few modifications, this could be a replacement for a no longer available voltage regulator, or for someone who doesn't want to part with $250 for another "magical mystery module". A lot of Chinese "throw away" generators are flooding the market, with no parts availability, and if someone could score a free unit with a bad voltage regulator, this is just the ticket (modified for the unit, of course).

With more modifications, it could be used to add better regulation to one of the ST type genheads, or any other generator using a "harmonic winding" .

I'm just waiting for the right project to come along.
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