Alternative AVR for MEP-803a

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kavesman1

Member
49
11
8
Location
Douglas Ga
After a lot of of head scratching and research, I've found a suitable replace for the stock AVR the 803a comes with.

Here was the issue with mine when i got it...after i got it and got it to fire up, the voltage on the output terminals was on the low side. I did follow the TM to trace down the problem. The issue was the quad winding resistance...it was higher that the TM said was allowed. After calling a few rewinding shops in my area...and nearly having my jaw hit the ground a few times (on the price) to get the genhead rewound to fix the issue, i decide to experiment with what i had.

After checking around, i settled on a SX460 Stanford genset AVR to test. Here's the steps i took to install it:

1: Remove the Stock AVR.
2: Install the SX460 AVR. 2 of the 4 original mounting hole in the 803a will fit the new AVR. But it is physically smaller than the original.
3: IF quad windings are ok, then wire to these pins.(Pins 7-8 ) If NOT, proceed to Step #4
4: Disconnect/Cut/Tape the quad winding circuit from the harness at the terminals.
5: Install a jumper wire from the 120v sense line to the input/power of the new AVR. (pins 7-8 )
(Note: recommend installing a 5amp 120/240v rated fuse on this line.I haven't yet,but still operates fine on my 803a.)
6: Install 60 Hz Jumper. (pins C,60)
7: Install 120V operation jumper. (pins 4,3)
8: Connect Field winding circuit. ( pins xx,x / F1,F2)
9: The MOST IMPORTANT step: Disconnect the field flash circuits from the controlling relay. Accidentally blew the transistors in AVR....Twice...before i figured what was going on. When the field flash activates,the surge of electricity blows the
transistors in it.
10: Connect Remote Voltage Pot. (pins 1,2)
(The required Pot for this AVR is a 1K ohm 1/2 watt Pot.The stock pot in the panel will NOT work,as it's a 5K pot.If you don't
the correct pot,install a jumper wire to those terminals.)

Now, after connecting all the necessary wires to the AVR, here's what i did to get it producing power:
1: Start up the Generator
2: Make sure it's up to Operational Temp.
3: Set Frequency on panel to 56-57 Hz.
4: Adjust low Frequency pot on AVR till the Low Frequency LED turns on.Then adjust back a hair to get the lamp to turn off.
5: Adjust Genset frequency to 60 Hz.
6: Check Voltage at output terminals with contactor closed. Or at the accessory panel for 120v. If not at correct voltage, adjust
the voltage pot on the AVR untill correct reading is reached.
(Note: Make sure the new 1K/0.5 Watt pot is turned all the way down/CCW before setting the voltage on the AVR.This way
you can adjust the voltage drop when a load is applied to the genset.)
7: Check to see if the Voltage on the panel meter is stable with no load applied to genset. If the voltage is bouncing,adjust the
Stability ADJ pot on AVR till the voltage become stable.

Below is a wiring diagram and a pic on how it looks mounted in my 803A. Hope this info helps someone in the future.

SX460 AVR-Wiring to MEP-803a.jpg20180310_190651[1].jpg
 

wildmann79

New member
4
0
3
Location
Santa Maria, Ca
After a lot of of head scratching and research, I've found a suitable replace for the stock AVR the 803a comes with.

Here was the issue with mine when i got it...after i got it and got it to fire up, the voltage on the output terminals was on the low side. I did follow the TM to trace down the problem. The issue was the quad winding resistance...it was higher that the TM said was allowed. After calling a few rewinding shops in my area...and nearly having my jaw hit the ground a few times (on the price) to get the genhead rewound to fix the issue, i decide to experiment with what i had.

After checking around, i settled on a SX460 Stanford genset AVR to test. Here's the steps i took to install it:

1: Remove the Stock AVR.
2: Install the SX460 AVR. 2 of the 4 original mounting hole in the 803a will fit the new AVR. But it is physically smaller than the original.
3: IF quad windings are ok, then wire to these pins.(Pins 7-8 ) If NOT, proceed to Step #4
4: Disconnect/Cut/Tape the quad winding circuit from the harness at the terminals.
5: Install a jumper wire from the 120v sense line to the input/power of the new AVR. (pins 7-8 )
(Note: recommend installing a 5amp 120/240v rated fuse on this line.I haven't yet,but still operates fine on my 803a.)
6: Install 60 Hz Jumper. (pins C,60)
7: Install 120V operation jumper. (pins 4,3)
8: Connect Field winding circuit. ( pins xx,x / F1,F2)
9: The MOST IMPORTANT step: Disconnect the field flash circuits from the controlling relay. Accidentally blew the transistors in AVR....Twice...before i figured what was going on. When the field flash activates,the surge of electricity blows the
transistors in it.
10: Connect Remote Voltage Pot. (pins 1,2)
(The required Pot for this AVR is a 1K ohm 1/2 watt Pot.The stock pot in the panel will NOT work,as it's a 5K pot.If you don't
the correct pot,install a jumper wire to those terminals.)

Now, after connecting all the necessary wires to the AVR, here's what i did to get it producing power:
1: Start up the Generator
2: Make sure it's up to Operational Temp.
3: Set Frequency on panel to 56-57 Hz.
4: Adjust low Frequency pot on AVR till the Low Frequency LED turns on.Then adjust back a hair to get the lamp to turn off.
5: Adjust Genset frequency to 60 Hz.
6: Check Voltage at output terminals with contactor closed. Or at the accessory panel for 120v. If not at correct voltage, adjust
the voltage pot on the AVR untill correct reading is reached.
(Note: Make sure the new 1K/0.5 Watt pot is turned all the way down/CCW before setting the voltage on the AVR.This way
you can adjust the voltage drop when a load is applied to the genset.)
7: Check to see if the Voltage on the panel meter is stable with no load applied to genset. If the voltage is bouncing,adjust the
Stability ADJ pot on AVR till the voltage become stable.

Below is a wiring diagram and a pic on how it looks mounted in my 803A. Hope this info helps someone in the future.

View attachment 721436View attachment 721437
Thank you for all this information. I have bought one and getting it installed now. How and where do I disconnect the field flash circuits from the controlling relay?
 

kavesman1

Member
49
11
8
Location
Douglas Ga
As far as i can remember, and looking at the TM pinout diagram i just looked at, the wire i disconnected from the K15 relay was the 105D circuit on pin 4 of the relay socket. pretty sure it just a screw terminal. Disconnect that terminal and tape it up. It helped me with the SX460 AVR from blowing its transistor.
 
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