MEP-002A Over Voltage issue, replaced regulator, still there

[Milhouse]

I have an MEP-002A that I just replaced the regulator on because I have a 320V output, and its still the same, checked all wires (I'm a tech and work on these all the time), checked to make sure i had no loose connections on the bus bars, control box plugs etc... everything seems ok, voltage dial has no effect at all, solid 320V output (and yes, phase switch is ok, cycled it to make sure I had good contact too) is there somthing else that might cause this to not regulate?

 

[Triple Jim]

Did you get my email, Chris? Just to save the board folks from duplicating, here's what I sent:

I assume you have a copy of the schematic in TM5-6115-585-34. The
control circuit is from T1, into the regulator at terminals 15 and 16,
through the full wave rectifier in the regulator, out terminal 14, into
CVT1 at C2, through the control windings, out C1, and back to the
regulator at terminal 17. Anything that breaks that loop would allow
the generator to go to full, unregulated output. TM5-6115-585-34
specifies the resistance from C1 to C2 as 9.6 ohms, ±0.96 ohms.

On top of all that, the regulator gets its voltage sample from T2,
connected to terminals 10 and 11 of the regulator. If T2 is not
supplying that voltage, the regulator will not supply any control
current to CVT1 and the generator output will go high.

Good luck and please let me know how you do.

 

[Isaac-1]

While the AVR board is a common cause of this there are a number of other things that can cause this. I recently had a MEP-003a with a similar problem, I eventually tracked it down to a T2 transformer that was installed backwards.

Ike

 

[jamawieb]

I had a similar issue with a recent unit. Check you T2 transformer, below are causes of high voltage and the very bottom has the instructions on how to check the T2 transformer.

18. HIGH GENERATOR OUTPUT VOLTAGE (NO LOAD).
Step 1. Check for voltage regulator failure. Remove voltage regulator lead (wire 39C16) from terminal 17.
If voltage goes even higher, the voltage regulator is good.
Test and repair defective regulator (paragraph 6-6),
Step 2. Check voltage adjust rheostat (R1).
Replace rheostat (R1) if necessary.
Step 3. Check current voltage transformer (CUTI) (paragraph 6-9b(7)).
Replace bad transformer.
Step 4. Check transformer T2 (paragraph 4-38( 15), TM 5-6115-584-12).
Replace bad transformer.




(15) Transformer (T2) (see figure 4-33). Tag

and disconnect four leads to transformer T2. Check

primary winding by measuring resistance from terminal

H1 to H2. Resistance should be 155 ohms

± 15.5 ohms. Check secondary winding by measuring

resistance from terminal X1 to X2. Resistance should

be 18.8 ohms ± 1.88 ohms. If either of the windings

do not show the proper resistance, replace transformer

 

[Triple Jim]

Jamawieb, I did miss suggesting that the front panel rheostat be checked, thanks. If that's not properly connected, or has a higher resistance than it should (open circuited) then you would also have the generator's output go high. That could be checked by simply shorting terminals 8 and 13 on the regulator board together and looking to see if the generator's output drops to normal or a bit below normal.

 

[Milhouse]

thanks all

Thanks to all that contributed, I'm going to go through the suggested steps and see what stands out.

 

[nortonl]

Any update? I have this problem also.

 

[Chainbreaker]

Any update? I have this problem also.

His problem reported 9 yrs ago, whatever it was (he never reported back with cause or solution), and his solution may not be pertinent to the cause/solution for the problem(s) you are experiencing.

What exactly are you experiencing & what trouble shooting have you performed so far?

There is a lot of very good troubleshooting information contained in posts #2 - #5 above that point you where the problem(s) might lie. You will need to do some of the above-mentioned tests to isolate the issue(s) you are experiencing.

For example... I had a similar problem, voltage went high, and it turned out to be a broken lead coming out of the T2 transformer winding that was supposed to be attached to the screw tab where a wiring harness cable's screw tab lead attaches to. Over time it apparently succumbed to excess vibration caused by bad cabinet vibration isolator mounts. Was hard to spot but with close inspection of all wiring I found the culprit! Bought new T2 transformer & replaced cabinet mounts & problem fixed. Your problem could be anywhere within that regulation circuit path... wiring issue, faulty component etc.

 

[Guyfang]

Nortonl,

Would suggest you start your own thread. This one is older then dirt, and you would get more help if you open a thread just for your problem.