mep-002a output problem

[tcastcas]

Hello all, i have a mep-002 with 60 hz at conveninece outlet but no voltage. the frequency is adjustable 50hz to 78hz and steady. thought someone may have an idea of where to start trouble shooting before i begin. thanks in advance

 

[Isaac-1]

How are you measuring frequency? just wondering as it generally requires voltage to the meter

Ike

 

[Speddmon]

Like Ike said, if you're using the onboard frequency meter, you have voltage. If this is the case, then your problem probably lies in the main beaker.

 

[Triple Jim]

I don't mean to insult you at all, but if you're measuring frequency at the convenience outlet and not getting a voltage reading at that location, having the meter in the DC volts range could explain it. Or are you measuring a voltage, but it's very low?

 

[tcastcas]

voltage

using a Fluke DVM, reading less than a volt AC at the convenience outlet

 

[tcastcas]

mep

Should have added no reading on the freq or voltage meters on the front panel

 

[Isaac-1]

If you turn the start knob back to the start position while the generator is running does the voltage momentarily spike then fall back off? There is a safety that should prevent the starter from engaging while the engine is running, also have you ever let the generator run at less than operating speed? If so you probably burned out your AC voltage regulator (never idle one of these generators).

Ike

 

[tcastcas]

mep-002

ill check if there is a spike in the voltage when the starter switch is engaged while running. don't know if this generator was ever idled. i'll make some quick checks on the voltage reg panel. It does not appear to be all that complicated of a board. thanks all for the suggestions.

 

[storeman]

Have you held the start switch an extra 10 second or so (after engine starts) to flash the field?

 

[tcastcas]

mep-002

hello Jerry, i flashed the field a couple of times, going to monitor the voltage as Ike suggested while flashing and go from there. do need another part, ill email you about it. thanks

 

[Isaac-1]

The most common failure parts are the diodes in the exciter rectifier bridge and the output transistor on the AVR board. The most common failure mode for the transistor if for the voltage to go high.

Ike

 

[tcastcas]

thanks Ike, the AVR board appears to be ok. the 3 transistors are fine and the diodes also check ok. No open resisters either.

 

[Isaac-1]

Well then the next step would be checking resistance in the windings, and to frame by megger if possible, by standard multi-meter if that is all you have.

 

[tcastcas]

Thanks Ike, haven't heard megger in a long time. my first career was in electronics, mostly R&D video applications and power supplies for aircraft use, that was 15 years ago. don't have a megger but i can dust off the old Leader scope and use a freq generator and power supply to "ring" the windings. First i'll go through every connection and plug on the unit. Do you see many of these units with bad windings?

 

[tcastcas]

after going through all the connections the genset has good output thanks for all the input. my meters, Hz, voltage and percent of power not working. there is a jumper in the wiring diagram between pins 8 and 9, it is not jumped on my vr board. does anyone know if some boards omitted this jumper?

 

[Speddmon]

The jumper should be a little metal molded piece right on the board, it can be tricky to see. Check it really closely to see if it is there or not.

I can't say for sure what if is even for, but if it is supposed to be there, I would make sure it is there. However, this should have no affect what-so-ever on your meter issues.

 

[M725]

Should have added no reading on the freq or voltage meters on the front panel

I had the same problem. You need to open the front and side elec panels and inspect to see if there is any damage like burn resistor or any thing thing else is burn up.
If you can not see anything you need to look in the 584-34 manual page 2-10 and start there at number 16.
I was lucky it stood out like a sore thumb I had a burnt resistor on the Bridge Rectifier Assembly (figure 6-11 )