Looking for some technical in put. Have a GMC/Homelite 1Kva generator with a faulty AVR module Have replaced the blown IRFS640 Mosfet & checked the 2N5551 transistor which is ok. It still wont work so I cracked open the resin from the PCB & tried to draw thecircuit to the best of my ability, some resistors broke so cant measure them. Surely there is a retired Electronics Engineer here who can tell me if my circuit is corect & likely to work, & what the value might be of the resistors which are unmarked, or any other things that might be wrong. I am keen to rebuild a regulator as there is only about 20 parts in it, & cant see why they are worth about $200. Have included voltages to the rotor under various loads by forcing the generator to work, by rectifying the 90V ac & feeding through a 40Watt resistor to the rotor. At least this proved the generator works & the AVR is faulty.  Help!!!   Daryl

Just noticed C1 should be betwean R1 & R5. Daryl

Sucsess at last have posted the corect & fully working circuit for the AVR unit. The easies & cheapest way was to remove all the parts & start again with new parts, only parts re used was the large cap & trim pot. If to was to replace all 24 components the cost woul still only be $14. So realy happy with the results, The C1 capacitor was also faulty & was only 16V rated so was replaced with a 35V unit as there is 18V across it.  Daryl

The final result, the AVR unit is now mounted  in the black box under the fuel tank & bolted to the front panel as it wont mount inside the end on the generator now.

Well done  .... 

Just noticed this post & was about to mail it to an electronics guru mate. 

Won't have to worry him now. Though I'm certain he would have redesigned the circuit & added a  range of bells & whistles.  That is if it ever got to the top of his list or grabbed his creative attention.

Good on you for sticking with it most people would dump it for scrap and get a new one . I have 2 of them in the shed .. both go .. The way to go..fix it its more fun..

yes.... well done on fixing this problem, and great to know so many others are keen to help.

Redtails , That car you have there needs a little bit of paint and it would be a goer.. It also needs some air in the left hand tyre.. Other than that it looks good..I see the air con is working well.........