Electronic Parts Replacements Info for the MEP-802A

MEP skin work

While the weather was not cooperating, i did some sheetmetal work on the missing skins.
It's nice to have a second MEP and have templates for the panels.

So far I have the top cover and exhaust flap done. I also need a front panel cover (instrument side. For others that's the back side) and the door by the coolant bottle side; but i need to locate a pair of locking mechanisms first.

Any suggestions on paints? I may try stove paint but the color is not going to match for sure.

I thought I got a reprieve from the rain, so I started to take some readings off S1 and the diagnostics connector.
The four S1 common pins have the 24V. Still no voltage going to the main fuel pump and shutoff solenoid.
Back to the schematics, and of course it started to rain again.

KB3BF,

This is what anyone who really needs the schematics and wire diagrams, needs to do. We kept some of the schematics that came in extra TM changes, in the 70-80's. Back then the schematics and wire diagrams were MUCH larger. We put them on a series of plywood sheets, covered in acetate. Traced out the start, run, aux fuel, main contactor and any other circuit we needed in colored wax pencils. Simple, and wire numbers were easy to read. Pin numbers on cannon plugs were MUCH easier to read. We printed out all the big cannon plugs. It made life much better for us. The schematics for the 802 and 803 are crap.

kb3bf said:

I forgot to mention:
1. the crank switch is in Normal position, and
2. Emergency switch is pulled back.

Click to expand...

By crank switch, you mean S-10, the Dead Crank Switch? By Normal, you mean the RUN position? it says normal on the schematics, but on the set it says run.

The Emergency switch, S-17 should be out, to let voltage go to the various control panel functions. The S-17 was for years a big problem.

The diagnostic canon plug, (J-3) is worth its weight in gold. But no one uses it. You can take voltage measurements and check to see if some of the important sub systems are working or getting voltage. Some smart guy (hint, hint) out there should make a small panel/box with a switch, to plug into the the J-3. The switch needs to have as many positions as the various test points on the schematic has. I bet some smart guy could make a simple, cheap piece of test equipment and perhaps be able to sell them for enough money to pay for his time and parts. AND, help out a bunch of people in SS. I would get a cannon plug to fit the J-3, and take off the threaded ring. You don't need to screw it in the J-3, just stick it in.

Just saying.

I think S1 is having issues, but for them moment I am able to start the engine from the front panel after a few tries.
S1 sometimes is developing 4V drops, occasionally throwing off some the electronics but after a few tries it seems to be OK.
However the MEP is not producing power, even with the battle switch on. S17 is OK. S5 does not do anything in the momentary OPEN position.
The AC Voltage Reg. did not blow the 3A SB fuse I added, but I need a schematic before I can follow what the Regulator is supposed to do.
I am off to Kinko's to make some large prints. Of course it stopped raining.

One more measurement off J3 shows no E-F exciter field voltage.
The Regulator? Need that schematic!

PS. Guyfang is right, J3 is really useful. Makes life a lot easier once you find the right size pin for the J3 connector.

Chainbreaker said:

The "Post Counter". Just wanted to post this answer to up my post count!

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Does the "Post Counter" give out battlefield commissions?

Chainbreaker said:

The "Post Counter". Just wanted to post this answer to up my post count!

Click to expand...

Can one be demoted for stupidity or not following the rules?

Your exciter voltage comes from the S-1 during the start phase. Look at the S-1 schedule and see what wire, (pin 3 or 7 on the S-1, if I remember right) is for the excitation.

Guyfang said:

Your exciter voltage comes from the S-1 during the start phase. Look at the S-1 schedule and see what wire, (pin 3 or 7 on the S-1, if I remember right) is for the excitation.

Click to expand...

You are correct Guyfang, the Start function for S-1 is 3, 7 to common.
Perhaps S1 is the culprit for this erratic behavior. I am switching S-1 from the other MEP.
While it is still a hit or miss to get it to start, it is doing it more frequently.

While I was away getting the schematics, my wife told me a bluejay flew on top of the MEP; sure enough it was still there when I went to the back yard. Of course it flew away when I got too close. I am so sorry I did not get a shot of it with my camera.

Anyhow, when I started the generator to my utmost surprise the MEP produced power for the first time, even before I had the chance to go over the schematics (see first image). I am calling this surprise change of events the "bluejay-effect". In reality I believe the bluejay was attracted by the lilly-pond, and had a good view of it from the MEP.
(Oh oh, watch me get demoted for mentioning all this lunacy, but I hope the bluejay does come back).

Let's see how well it scores for reliability long term under a hefty resistive load (see 2nd image). That is after I ground the MEP since it seems to be producing "juice" now.
I will try to rewire the load for three phase 120V. There are 3 coils and they all seem to be the same. The label says it has a max rating of 15KW at 240V. At 208V it should be more like 12KW and at 110V the MEP should handle it if around 6KW or less, hopefully this one also. Now comes the more dangerous phase of the job.
To be continued.....

If you have kids, dogs and yes, even cats, please enclose that thing! I have been "hung up" on voltage twice in my life. Not something i would wish on my worst enemy. It does sound like just what you need to load test.

kb3bf said:

Can one be demoted for stupidity or not following the rules?

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As for stupidity...no seems just the opposite. The less one knows the more questions they will ask, the more questions they ask the higher their post count which eventually leads to a rank promotion and more knowledge on their part. We are all here to share, learn and enjoy anyway so that works out well.

On the other hand, if one does not follow the rules I haven't noticed anyone getting busted back to Private. Instead, they will usually get a message in the thread when/where appropriate, or perhaps a PM (Private Mail), from a M.P. (Moderator Police). If all else fails, I think the SS cyber equivalent of a Stockade is getting BANNED if serious enough.

Getting the MEP ready for a 100% load test.

I replaced S6 and added an MOV to pins 7,8 of the AC Voltage regulator to suppress any transients that may be generated during hard starts.
The AC clamping voltage is about +,- 250V peak to peak. The fuse mod has already been done.

So far the generator starts up easily, but I kept tripping the overvoltage circuit.
Finally I realized that by setting the voltage adjustment knob to a minimum and adding a load seemed to resolve the problem. The real tests involving a 100% load, have not started yet as I am still working on the grounding and the branch circuits.

I am ready to do a third oil change due to having rainwater in the engine when I first got it, add fresh fuel and flush the engine coolant. Also what is that reset feature on the air filter canister for?

When the air filter gets to a point that it starts to clog up, naturally, it has to work harder to draw air in. A small red flag will appear in the round plastic Air Restriction Indicator, letting you know its time to check/clean the filter out. When you have done that, simply press the button and the red flag will reset, lurking there until the next time!!

Your picture of S-6 is worth a thousand words, (again). When someone wants to know why the switches go bad, this picture is perfict. Notice that the openings where you can insert wires and tighten them, allow dust and dirt to enter the switch. Sooner or later, the switch gets harder and harder to turn. Or gets blocked, in an extreme case. Snap goes the shaft, or, nothing happens. When the original contracts were let for a switch, no one really planned to spend the next couple decades in the desert, or other really harsh environments.

I second what Guyfang just said in the previous posting.

I took S6 apart and found many of the contacts to be very dirty. I am going to take S1 also apart and see if I can clean it, add some WD40, and use it until I get the upgraded switch.
At least I have a replacement for the older version if something goes wrong and I can't reassemble it. The older S1 and S6 switches appear to be compatible and modular to each other. I will be able to tell once they are taken apart. I just have to be careful as there are several springs under tension and they will go flying if not removed first.

The schematic has CR4 on pins 7, 1 (diode anode on 1) of S1.
What is the function of this diode?

CR4 routes the B+ to the Pre-Heat Relay in the START position, but why? Cold weather reasons?

It would appear the design is to activate the pre-heat during cranking. I assume the intent is to have the heaters remain activated after you manually do a pre-heat and go to start the engine. Keeps the heaters from cooling while you are cranking the engine during a cold weather start.

Hi KLOPPK,

thanks for the CR4 explanation. That makes sense.

I am not surprised there are issues with the older MEP switches as the hardware used has the wrong mix of metals causing corrosion and the switches are not sealed from the environment. It would have been better if everything had been plated the same metal (preferably silver) or had used brass hardware only. Most screws that were in contact with jumpers are corroded and frozen. One set of contacts measured several thousand ohms in the ON state. Perhaps the plastic shafts get broken when folks frustrated by the erratic switch behavior, increase the torquing while switching. I am including an image of what the hardware looks like inside these switches.

Luckily there are enough good wafers left from the S6 switch I replaced to build a complete S1 from scratch.

...but I am still looking for that newer S1 version.

Guyfang said:

If you have kids, dogs and yes, even cats, please enclose that thing! I have been "hung up" on voltage twice in my life. Not something i would wish on my worst enemy. It does sound like just what you need to load test.

Click to expand...

....there are a few obnoxious squirrels (that keep trying to get into the house) that I would like to get rid off.....

Turns out I could not use it. The resistive elements were too brittle and broke in pieces. I will use a pair of space heaters instead, and that will be around 3KW only. So I'll add a toaster and my wife's hair drier. That should do it. I will set the MEP for 120V, single phase.

The springs were why I stopped fooling with rebuilding switches. The darn things had a bad habit of finding greener pastures. Or rolling away. But the biggest reason was that the army had an unlimited supply of switches. I the time I needed to take a S-1 or S-6 apart, I could replace 4 switches. And not use a swear word even once!

Perhaps you could put out the word that you will fix every switch that comes your way! Keep you out of trouble for several years in any case. Now the S-8, that baby was much easier to take apart and "repair". Its much bigger. You don't need a magnifying glass to fool with it.