MEP 003a back together...but...

[hedgehog69]

I have been sputting a MEP 003a back together. I had a Melton rebuilt engine and a A1 gen head. I used the control panel from the old unit, but it was dead. Bad switch?? I didn't work to diagnose, I just swapped in one from a MEP 002a parts machine. I thought I had read they are the same. Unit fired up...coughed and sputtered a bit, but runs like a new one. But...generator not generating correct voltage. I got about 46v across L1 & L0.
I also use the 'side boxes' from the MEP 002a...so all electronics are off the MEP 002a. I was thinking I had read that these are interchangeable between 002a & 003a. My next step is to replace convenience outlets in the 'side box'...which is why I just swapped boxes, and use the original 003a 'side boxes. Back to the manual and some deeper digging here.

 

[Isaac-1]

You may have an output lead connected wrong, double check, also post numbers for L1-L2, L1-L0, etc. depending on voltage mode, mostly we would be looking at the right ratio here not the voltage. If the ratio is right it is probably your voltage regulator or transistors.

Ike

 

[Speddmon]

The output boxes (side boxes) use the same parts EXCEPT for the main breaker. The main breaker is only 1/2 the size of the 003a box. Also, the CT/CVT assembly is the same, but it has twice as many wraps of wire as the box on the 003a, so you're current readings will no be correct, unless you open the box and unwind some of the wraps.

 

[storeman]

You got a problem. The boxes are NOT the same, including the breaker and the windings. I am not sure about the voltage rectifier. Speddman probably can advise on the rectifier.
Jerry

 

[hedgehog69]

Thanks!! I was thinking I had read they were the same. The 110v outlets on the mep 003a were missing,so I thought it easiest to just swap out the whole box. Thinking got me in trouble again! Hopefully I can swap out the outlets and install the original box...will see where that gets me.

 

[Speddmon]

storeman, trust me, the boxes are the same except for the parts I mentioned above. If you swap out the breaker and take a couple of wraps of wire out of the coil assemblies then the 002a box becomes an 003a box. This is done because the control boxes (the one with the gauges) is exactly the same between the 002a and 003a.

 

[hedgehog69]

Well...got it back together with the original 'sidebox'. Fired it up...Hz guage to 60...all right!! Plugged in a light I had close...it lit up. Went back to test charge going to batteries...when I saw smoke coming from control panel box. Shut it down immediately...opened the door...smoke rolled out. Got smoke cleared out...saw smoke coming from T1 transformer....black 'rubber' dripped from transformer, but all wires going to it are fine. I didn't have time to test anything....the learning experience continues...

 

[Speddmon]

I would suggest that the T1 transformer was bad or going bad when you started. I only say this because the primary side of both T1 and T2 come from exactly the same source. And the secondaries go to the VR for both transformers.

 

[storeman]

Thanks Speddmon. Hedgehog, I may be able to help you on the T1. Pm me if you need it and I'll check availability.
Jerry

 

[hedgehog69]

Well....took T1 transformer from my parts machine...a 002a...and installed it on the 003a. Fired it up...all looking great...until I notice a couple of small wisps of smoke coming from the circuit board. I will get out there later this week and see which resistors(?) fried. Thanks again!! I really appreciate the knowledge. I do get a bit frustrated when tinkering, but it sure feels good when I get things worked thru!

 

[hedgehog69]

After the transformer swap, I fired it up...went well until small wisps of smoke on circuit board. CR7, CR8, and CR9 are fried. This was a MEP002a box going onto a MEP003a. I am now swapping in the MEP003a board. Is possible the frying transformer might have caused these resistors(?) to fry?

 

[hedgehog69]

Trying to upload pictures...no idea why I can't get it to work on SS.

 

[hedgehog69]

Got the 'new' circuit board in..fired it up...have ran it for 5 min or so...looking great!! Now..back to battery charging system...arrgghhh. getting 24.8 at the batteries...and it is holding. Thinking if it was working right, it should have started going up in the time I ran it. Got a new voltage regulator at work. Might run it some more ...do a couple of the tests on that system. Engine is a fresh rebuilt...wouldn't think it would be bad, but.....

 

[Speddmon]

Those DC regulators are most definitely the weak link in the MEP-002a's and MEP-003a's

 

[hedgehog69]

When I took one of the other units I had to the electric motor shop, I was hoping they had an alternative to that VR....something more modern...more 'forgiving' if unit idled....but they had nothing

 

[PeterD]

... have caused these resistors(?) to fry?

CRx signifies a diode, not a resistor. A resistor would be Rx, and a capacitor Cx. Transformers Tx, while vacuum tubes Vx.

 

[Speddmon]

When I took one of the other units I had to the electric motor shop, I was hoping they had an alternative to that VR....something more modern...more 'forgiving' if unit idled....but they had nothing

You might be confusing the DC regulator with the AC regulator. The DC regulator doesn't give 2 cents whether the engine is at idle or not...the AC regulator however certainly does care.

 

[hedgehog69]

You might be confusing the DC regulator with the AC regulator. The DC regulator doesn't give 2 cents whether the engine is at idle or not...the AC regulator however certainly does care.

Is the one under the shroud. Part # 2920-01-038-5252

 

[Speddmon]

Yes, that is the NSN for the DC regulator which is located under the cooling fan shroud. Again, it's not the DC regulator that will be damaged by idling the engine. The AC regulator does not like to have the engine at idle.

 

[storeman]

It is confusing. I've had folks pull AC regulators out of their 003a boxes and give me 002a part numbers for what was on their units. There is a physical difference between the two boards, but apparently they have been installed as interchangeable. Anyone know for sure?
Jerry