MEP-804a Voltage/Frequency troubles

[justinfaith]

Hi guys,

I'm having a spot of bother with this 804a genset that I got a few months back. It seemed to be operating fine (under no load) whenever I would crank'er up here and there. Anyhow, now that I'm getting close to actually using the thing, it started acting up. It started when the upper left relay (behind the control panel) burned up, which I replaced along with the socket. Ever since then the voltage and frequency read as they should only when I am starting the genset, and the Master Switch is in the 'Start' position. As soon as I let it go to 'Prime and Run', the votage spikes then goes way down, as well as the Frequency (rests @ about 52Hz when set on 60Hz). Pics are posted for both positions. Also, I noticed some browned wire tips coming off some of the resistors (shown in the pic below). I'm sure that can happen during the initial soldering job, but...

I'm fairly mechanically inclined, but I figured I'd see if any of you kind folks would have any advice as far as where to start poking around.

Many, many thanks!!!

 

[Guyfang]

What relay did you replace. "upper left Relay" is unclear. Next to every component is, in white, the component ID. I think you are talking about a switch. So take a gander in the set, and maybe in the TM, and let us know.

 

[justinfaith]

Many thanks for your response. Apologies for being so vague. The ID# is K15 . There are 2 stacks of 4 of theses identical relays inside the control box, right next to the resistors pictured above. Part#77342 KUP14D15-2 RELAY, ELECTROMAGNET. Here's a pic of the base of the fried unit while I was replacing it...

 

[ronneyreal]

i have mep 804 b will not produce elec i replace voltage regulator with a new one from flight systems old one would blow 3amp fuse still no power after i let off start switch.

 

[Guyfang]

Many thanks for your response. Apologies for being so vague. The ID# is K15 . There are 2 stacks of 4 of theses identical relays inside the control box, right next to the resistors pictured above. Part#77342 KUP14D15-2 RELAY, ELECTROMAGNET. Here's a pic of the base of the fried unit while I was replacing it...

Does your gen set have the fuse mod hooked to the A1, (volt regulator)?


Sory it take me so long to get back to you. been in the hospital a little over two weeks. Now at home, but flat on my back.

 

[Guyfang]

i have mep 804 b will not produce elec i replace voltage regulator with a new one from flight systems old one would blow 3amp fuse still no power after i let off start switch.

OK, the old volt reg is bad, if the fuse blows.
Did you by any chance hard wire the fuse, to test or see if it would work, before changing the Volt reg?

 

[ronneyreal]

No I did not hardwire the generator I did put another 3 amp fuse in it . The fuse that I used was not a fast blow type fuse one vendor said it would be okay so I tried it didn't work. So I sent the regulator off and had it repaired got it back and it ran for about 5 minutes producing power and then I shut the unit off and started it back and it blew the fuse again and would not work so then I put a different regulator on it from flight systems

 

[ronneyreal]

I have the fast-acting fuse in it now because I talked to another vendor and they said to use the same type that was in it

 

[ronneyreal]

The way I have it wired now the primary Supply wires to the Transformer are inputs to the new regulator I have the new regulator has an output to the F1 and F2 positive and negative. Four wires total I'm wondering if it will work like that because the old regulator is out and all those wires that were hooked to the old regulator I taped them up and label them the various outputs of the Transformer on the secondary I got those taped up

 

[ronneyreal]

I put that flight systems model 480 Universal regulator on this genset capable of 90 volts DC at 5 amp. I have the the field positive output of the regulator going through that 3 amp fuse so that it's still protected at the factory rating

 

[ronneyreal]

I ohmed the field positive and negative they ohm at about 35 ohms if I remember right and they're not going to ground either

 

[justinfaith]

Yes, it does have the fuse... it didn't look blown, but I'll check it tomorrow. Man- hope everything is going well towards recovery!! Many thanks good sir.

 

[Guyfang]

I ohmed the field positive and negative they ohm at about 35 ohms if I remember right and they're not going to ground either

So so what is in the TM for checking the windings? How many ohm's?

 

[justinfaith]

Does your gen set have the fuse mod hooked to the A1, (volt regulator)?

Yep, fuse tests that it hasn't blown...

 

[Guyfang]

Tell me, that the old VR and the new VR are the same, exact kind. There are two kinds, and you can NOT mix them. Libby and the one shown in the picture.

 

[justinfaith]

Well, I found the problem... a 14 pin chip inside the Volt Reg. Any idea what this is- since any part info is burned off!? Strange that the fuse didn't blow; but I guess it makes sense that a failed relay could cause this. If I have to replace the whole VR, are there any interchangeable part #s I can search for? Thanks for any advice!

 

[justinfaith]

So I figured out that the TRC 19890-002 400 Hz circuit board is the same (19893k stamped on the lower rt corner of the board) as my 50/60hz 19870 model. There are a few different parts, but it should swap out fairly easily. Thanks all for your help!

 

[Guyfang]

The naked card is the same. The components on it are different. Install a 400 hertz VR at your own risk. They are different for a reason. NOT interchangeable.

 

[justinfaith]

Oh yes, I understand that they are not interchangeable! I'm talking about the circuit board only. I'm using it to build a 50/60hz, as most of the components are the same, minus a few differences. Those differences NEED TO BE CORRECTED before a swap is possible! That being said, it's an easy board to mod...

 

[Guyfang]

Keep us informed. I think that this is great news for the future, say 5-15 years down the road. Sadly, the parts are not called out in the -24P, like in the older gen sets.