MEP-804B putting out only 50HZ

[Caliglas]

I checked the MPU as recommended from a friend and it's 2.5 and the switch is set to 60HZ. It ran fine half way thru Milton running AC pool pump and everything else fine. All of a sudden the AC fan outside was running slow. I checked the frequency and it said 50HZ. While running, it pops up for a split second to 60 or so. My friend thought it was surely the MPU. The PEC potentiator behind the frequency knob is corroded. Nothing else on the machine shows any corrosion like the PEC pot. I ordered a new potentiator and will solder it on this week. Anywhere else I can look? FWIW the only reason I know about the MPU is the info from a friend. I'm pretty good mechanically but electric can be trying. Jerry

 

[2Pbfeet]

Welcome! Any photos?

All the best,

2Pbfeet

 

[Guyfang]

What position is Item 27 in?

 

[Caliglas]

Welcome! Any photos?

All the best,

2Pbfeet

Yes. The voltage potentiator is just as bad

 

[Caliglas]

What position is Item 27 in?


View attachment 946951

G

 

[Caliglas]

GView attachment 946954

60

 

[Guyfang]

I believe I would start here. Good eyes. I might try de soldering the R1 and then cleaning the terminals up. Then re-solder and give it a try. The funky terminals may be making contact to the control panel door.

 

[Caliglas]

Yes funky is appropriate. I have a new one coming in tomorrow. I might get another for the voltage too. I’ll let you know inna few days. Thank you

 

[Caliglas]

I replaced both the frequency and voltage potentiators and nothing has changed. The HZ frequency is at around 52 and the knob adjuster changes nothing. FWIW the voltage at the 120 receptacle is around 138 volts.
Also, since I bought this I have been using it as a single phase gen using just 2 output legs. In my search for answers I found a YT video explaining how to properly change it to a single phase gen. If and when I get this fixed I will be doing that. The video is very clear on what to do and looks easy enough.

 

[Caliglas]

Anyone have a clue??

 

[Guyfang]

@LuckeyD

 

[LuckeyD]

I bumped something and lost it all. Been busy with inheritance. An SMS says I'm supposed to say where i am. I'm in Karlsruhe Germany, fixing to go to Vilseck sometime this week to cut grass. OK, I have a clue! GIs had this all the time and I was the answer man so here goes. Tried to read the string and you say it went to 50Hertz all of a sudden. If you had it at 60.5 hertz it is probably running at 50-50.5 hertz. Please leave the Mag pickup alone unless you have starting issues. I did not receive anything until Guy sent me a note on this. OK, the blue A5 module controls this. The freq POT on the front panel is easy to check and someone tried to get you to test this. Everything OFF, CB1 pulled, remove wire 192B from Terminal 7 and using a Multimeter, measure resistance of 0-5000 ohms as you rotate the POT on the front panel. No bad spots, if all is well reconnect that wire. Ensure the s12 on AUX control Panel is set to 60 HZ. Set everything correctly, and start the thing. It is still at 50 HZ so now do the following; Shut down, pull CB1 again, and connect a test wire from Terminal 3 to terminal 1 of the A5 for this test. Remove that wire 152A and insulate it leaving only that test wire from terminal 3. Now start the gen. Reading 60HZ? If yes you have a S12, or K21, or wiring issue. The A5 must get 24VDC at terminal 1 to run at 60HZ. No 24VDC, you only get 50 HZ. Removing the test wire after shut down, you can test K21 by swapping that relay with K19, used for AUX fuel. Recommend getting the schematic and A5 module adjustments from the forum. Let everyone know how this goes......