MEP-804a Voltage/Frequency troubles

justinfaith

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Still troubleshooting this thing, but I've got the circuit board from a 400hz VR converted to 50/60. Bench tests out OK. I'll give a parts list soon...

Also, my initial trouble seems to have stemmed from a short in the Voltage Adjustment circuit, starting with potentiometer R1. I'm following the circuit in the manual, and I can't find R16 (probably overlooking it somehow)!! Can anyone help me out??
Thanks!!
 

Guyfang

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There is a switch in the control panel. I forget the switch number, and do not want to limp on crutches two flights of stairs. Anyway, the switch is labeled 50/60 hertz. It's on a small plate. You can't miss it. Look behind the plate. Should be a resister there, hooked to the switch. That's R16. It's a tough one to find, unless you have ever replaced the entire V/R kit.
 

justinfaith

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Found it- (1ohm resistor soldered to the switch) and it was fried! Hope that fixes my woes... A leg of the voltage pot broke off (shows signs of having shorted) so I'm waiting for a new one to arrive before i can test the whole business... Thanks as always!
 

YohanM

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Homestead FL
Found it- (1ohm resistor soldered to the switch) and it was fried! Hope that fixes my woes... A leg of the voltage pot broke off (shows signs of having shorted) so I'm waiting for a new one to arrive before i can test the whole business... Thanks as always!
Hello Justin,

I just got an MEP804A, I am having the same issue you were having. If I keep the start knob twisted to the right the Hertz and Volts work, but as soon as i let go they both come down and stop working.

I am wondering if you ever solved your issue and where did you get the parts from.

Thanks in advance for the help.
 

Guyfang

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Have you downloaded the TM's.
If so, have you looked at all levels of troubleshooting?
Is this set new to you? Or have you seen it work right at some time?
Can you get along with Schmatices?
 

YohanM

New member
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Location
Homestead FL
Have you downloaded the TM's.
If so, have you looked at all levels of troubleshooting?
Is this set new to you? Or have you seen it work right at some time?
Can you get along with Schmatices?
Yes I have downloaded the TMs but couldn't find the issue I am having to be able to troubleshoot it, so I did a search and found that I has the same problem as Justin.

Yes this set is new to me. It is actually my first and just received it this past Tuesday. I have never seen it work.

I am in the aviation field to I am familiar with Schematics but not very knowledgeable when it comes to Electricity.
 

Guyfang

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I tested the fuse for continuity and it seems to be blown. I have ordered a replacement.
Order two, at least. Do not jump the fuse holder. The fuse is there to protect the QUAD circuit, when the volt regulator is bad, in an over voltage situation. When you put a new one in and it blows, your volt reg is probably bad. Hence, get at least two extra fuses.
 

YohanM

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Hey Guyfang, I finally got the fuse. Installed it, turned it on and it worked for a sec and then it blew the fuse again. It also turned on the over voltage light. Once I turned it off and on again it the over voltage light turned off and the under voltage turned on.

Is it for sure the voltage regulator?
 

Guyfang

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The only reason the fuse is there is to protect the stater winding's, when the Volt reg goes into over volt mode. That's why when you started it, The S1 switch provided initial excitation. The main gen started to make power. The volt reg took over the exciter function. The volt reg was sending maybe 600 volts to the exciter winding's, so the set went into over volt mode. The fuse blew, keeping the stater winding's from being destroyed. Then you reset the fault, but it will not make power due to the fuse being blown, so it shows under volt.

It cant be anything else.
 

jmenende

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Location
Miami
No I did not hardwire the generator I did put another 3 amp fuse in it . The fuse that I used was not a fast blow type fuse one vendor said it would be okay so I tried it didn't work. So I sent the regulator off and had it repaired got it back and it ran for about 5 minutes producing power and then I shut the unit off and started it back and it blew the fuse again and would not work so then I put a different regulator on it from flight systems
Hello, where did you send the avr to be repaired and what was the approx cost?
 
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