MEP-004A, No output

[KLChurch]

Congrads Peter!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Kris

 

[peapvp]

View attachment 773628
is this it?

this could be it - check the wire numbers

 

[peapvp]

Kris,

You could also check with the Boneyard in California and ask for NSN 5950-00-600-0840

I am not sure how much they would charge you for it - but this way you would have the exact same transformer as replacement and keep everything original

So maybe we are back to the toasted transformer?
Should I go and buy the 37 dollar unit and ship it in?
Kris

 

[Guyfang]

View attachment 773628
is this it?

yes!!!!!!!!!!!!!

 

[KLChurch]

One side of the terminal is F1&F2
The other side D11G and cant see the other wire number.
Kris

 

[Guyfang]

One side of the terminal is F1&F2
The other side D11G and cant see the other wire number.
Kris

Thats it! The F1 and F2 wires go to TB1

 

[KLChurch]

What do I do now with F1 and 2?
Kris

 

[peapvp]

It looks like that F1 and F2 are the two wires on the righthand side of TB16, this is actually TB16
these two wires F1 and F2 have to be removed from TB 16 for the next test, after the transformer has been replaced

As of right now you can check the resistance between the removed F1 and F2 wire for verification of the first measurement on J13 R/S

I would not reconnect F1 and F2 at the moment until you have replaced the transformer and we did the voltage test on the wires which are still on TB 16
J13 has to be connected to A11 for this test to be performed. The best thing would be to do this over the phone when you have the new transformer installed.

 

[KLChurch]

OK
I will remove F1 and F2 and ohm between them
Then report back.
I will see if I can order the transformer you suggested today and will need instructions on how to wire it up.
Kris

 

[peapvp]

Ok Kris, I will make you a drawing when you get the transformer

I double checked - this is TB16

OK
I will remove F1 and F2 and ohm between them
Then report back.
I will see if I can order the transformer you suggested today and will need instructions on how to wire it up.
Kris

 

[KLChurch]

Thanks peter
Kris

 

[Zed254]

If Kris goes with this transformer - https://www.automationdirect.com/ad...sformers/240x480_vac_to_120x240_vac/sp100mqmj - should he buy 2 in order to have a spare (they are pretty cheap).....and/or some fuse holders / fuses to protect it? Where would the fuses go and what sizes are needed if this is an appropriate plan?

 

[KLChurch]

Ill buy 2. Good idea.
Also if fuses are good I am game for that also.
Kris

 

[KLChurch]

ohm between F1 and F2 is 2.4
Kris

 

[peapvp]

Ill buy 2. Good idea.
Also if fuses are good I am game for that also.
Kris

As to Kris and Zed254

I am typing this in WordPerfect as this is easier for me to read while typing, to eliminate missing words and typos.
This text box on the webforum is to small for me to read while typing.

I am going to try to explain the purpose of this transformer in as simple terms as possible and answer the two questions as to the fuse and on how many transformers to buy.

When the Generator is first started in Start position, 24 VDC are applied to the two wires F1 and F2 through the Start / Stop / Run Switch Circuit and associated Relays.

This initial DC Voltage then creates the initial magnetic Field in the Generator G1 while the engine is still cranking.

This initial Voltage is around 15 to 20 VAC while cranking

The transformer is directly connected with its primary Coil to L1 and L2 Output power hence the transformer starts supplying the Voltage Regulator Board with AC Power

Part of this power is also fed back into F1 via the center tap of the secondary side of the transformer.
F2 is tied to ground

As the Generator is revving up, the voltage on the primary side increases with increase in rpm,

this increases the supply voltage to the VR Board and F1 when the Start Switch is released,
the 24 V on F1 / F2 are removed and the unit is sustaining it self .

The combination of input voltage on the primary side of the transformer and power output on the secondary side supplying the VR Board and this creates now a constant voltage on F1 while the system is running.

Increasing the Voltage via the Voltage Rheostat / VR Board increases the Voltage on F1 and lowering the Voltage via the Voltage Rheostat / VR Board decreases the Voltage on F1 and so forth.

So far with the functioning of this circuit.As to the fuse. Yes on the primary side. A 3AG Type Fuse with about 5 Amps should protect the Transformer, VR Board and exciter coil it self.

All newer Gensets have this fuse. You can get a panel mount 3AG Fuse Holder and mount it next to the J13 Receptacle on A11 and label it.

With this fuse, there should be no need for a second transformer, as the fuse will blow now, cutting of power to the transformer itself when something goes wrong on the secondary side.

In Kris’s case, since the unit is no longer self sustaining after the Start/Stop/Run Switch has been released indicates a double failure:

1. The transformer overloaded due to a short on the secondary side and burnt out because there was no fuse protecting it

2. One cause of this short has been ruled out due to resistance check - the exciter coil

3. This leaves only the Voltage Regulator Board as suspect. The transistor Q5 and/or the 2 SCR’s are blown and have shorted.

This is the most likely scenario at this point. There is nothing else connected to the secondary besides the items listed above which can cause a short.

 

[KLChurch]

OK should I replace the A11 with the new one that has been tested?
Kris

 

[peapvp]

OK should I replace the A11 with the new one that has been tested?
Kris

Yes, then you don't need to buy the transformer as he is part of A11- but I would add the 3AG Fuse to the new A11....

 

[KLChurch]

I don't understand. I'm calling A11 the VR board. The transformer is the cooked sucker.
Kris

 

[peapvp]

OK should I replace the A11 with the new one that has been tested?
Kris

A11 is the entire assembly including board and transformer and various other parts - just remove the entire A11 unit out of your genset and take some pictures

One more thing Kris,

A Military Part/Assembly has usually only one NSN but can have multiple manufacturer part number associated with it's NSN

as multiple different manufacturers usually sell the same part / assembly to the Military under one NSN

 

[peapvp]

I don't understand. I'm calling A11 the VR board. The transformer is the cooked sucker.
Kris