MEP-803A Frequency Transducer Needed

[Waukesha]

I’ve got the genset up and running; the problem is that the hz meter doesn’t work. I was able to test the frequency at the output lugs (and convenience receptacle), and use the “frequency adjuster” to adjust the set to 60hz. So I’m positive that I’m getting 60hz @120v in both places.

I used the schematics that I found on this website along with the troubleshooting guide in the TM to narrow my search down to the A7 (Frequency Transduzer) and M2 (Frequency Meter).

I tested the frequency meter using my Amprobe 530 set to check resistance, and the gauge freely moves from 55hz all the way to ~63hz and back down to home @55hz once the meter is removed.

I then disconnected the Line inputs from the A7 and hooked up known 60hz 120v house power to the A7. Nothing registered across the +/- on the A7.

Part numbers found on the box:
30554 ASSY 88-21136
Technology Research Corp
FSCM 60177
Part No. 19260
19237B
S/N: TQ27089

That leads me here, in search of your help. Does my testing above indicate a back A7 (Frequency Transducer) as I suspect? And 2, where can I source one? I’m going to drill out the rivets and take a peek inside to see if I can’t find a bad component within. However, I’m assuming it’s a potted mess in there.
Appreciate any insight that you can provide!
JT

 

[Waukesha]

I ended up purchasing a digital meter from Mouser. I rolled the dice, I didn’t think that a replacement A7 could be procured for less than $40. http://www.mouser.com/Search/Produc...irtualkey58010000virtualkey580-DMR20-1-FM-R-C

 

[Waukesha]

I’ve got the genset up and running; the problem is that the hz meter doesn’t work. I was able to test the frequency at the output lugs (and convenience receptacle), and use the “frequency adjuster” to adjust the set to 60hz. So I’m positive that I’m getting 60hz @120v in both places.
I used the schematics that I found on this website along with the troubleshooting guide in the TM to narrow my search down to the A7 (Frequency Transduzer) and M3 (Frequency Meter).
I tested the frequency meter using my Amprobe 530 set to check resistance, and the gauge freely moves from 55hz all the way to ~63hz and back down to home @55hz once the meter is removed.
I then disconnected the Line inputs from the A7 and hooked up known 60hz 120v house power to the A7. Nothing registered across the +/- on the A7.
That leads me here, in search of your help. Does my testing above indicate a back A7 (Frequency Transducer) as I suspect? And 2, where can I source one? I’m going to drill out the rivets and take a peek inside to see if I can’t find a bad component within. However, I’m assuming it’s a potted mess in there.

Part numbers found on the box:
30554 ASSY 88-21136
Technology Research Corp
FSCM 60177
Part No. 19260
19237B
S/N: TQ27089

Appreciate any insight that you can provide!
JT

 

[Waukesha]

Not sure what happened to the original post, however hopefully you can see the pics and part numbers above.

I ended up ordering a Murata DMR20-1-FM-R-C HZ meter. There are complementing Voltage and Amperage gauges as well. For $40 (just for the HZ gauge), I didn't think I could locate a new (or simply working) A7 for that.

 

[csheath]

Here's what I did to mine. Not the neatest looking mod but very functional.

 

[Guyfang]

Just to complete the loop, if you have AC in, on the A-7 and no DC out to the meter, yeah, the A-7 isnt working.

NSN: 6695-01-384-7381
Cost to the military: $342.00
Throw away item, but I bet there are some smart guys here in SS who could fix or even improve it. As a rule, the A-7 was an item that very seldom went bad.

 

[Waukesha]

csheath - Very functional! Do the digital readouts align with your multi meter?

Just to complete the loop, if you have AC in, on the A-7 and no DC out to the meter, yeah, the A-7 isnt working.

NSN: 6695-01-384-7381
Cost to the military: $342.00
Throw away item, but I bet there are some smart guys here in SS who could fix or even improve it. As a rule, the A-7 was an item that very seldom went bad.

Thanks, Guyfang! I was looking for the NSN #, but couldn't locate. Where did you pull that from? If you look at the second to last picture that I posted; A7_Side4.jpg It looks to me like the large green capacitor next to the transformer may be leaking. Not sure if that could cause the failure?

I decided for $40, it's not worth my time to de-solder each component to try and located the broken component(s). However, if anyone on here wants me to test a specific component, I'd be happy to.

 

[csheath]

csheath - Very functional! Do the digital readouts align with your multi meter?

Actually the voltage reading on the green generator meter is a few volts low but the HZ is accurate. That was mainly what I needed that meter for since my frequency gauge didn't work. Both the voltage and amperage readings appear to be accurate on the two line load meters so I just add the two line voltages together. One line reads a .1A higher than the other because I plug the fan for my load bank into the convenience outlet.

 

[Guyfang]

csheath - Very functional! Do the digital readouts align with your multi meter?



Thanks, Guyfang! I was looking for the NSN #, but couldn't locate. Where did you pull that from? If you look at the second to last picture that I posted; A7_Side4.jpg It looks to me like the large green capacitor next to the transformer may be leaking. Not sure if that could cause the failure?

I decided for $40, it's not worth my time to de-solder each component to try and located the broken component(s). However, if anyone on here wants me to test a specific component, I'd be happy to.

Tell me what TM you are using, I will tell you where the NSN is. I just posted something on how to use the -10, operators manual, and maybe it time to do the same with the -24P manual. There is much info in it, and some of it needs to be dug out, so to speak.

Well, it would be nice to know what did go wrong with the A-7. Its a shame that it was coded PAOZZ. That way it always got tossed in the trash, when it was bad, instead of going back to the military to be looked at. I understand why, the part just didnt cost much, and shipping, handling, inspection, storage and paying someone to take it apart and find the bad component, just wasn't worth the effort. But still....................................

 

[Waukesha]

Tell me what TM you are using, I will tell you where the NSN is. I just posted something on how to use the -10, operators manual, and maybe it time to do the same with the -24P manual. There is much info in it, and some of it needs to be dug out, so to speak.

I have both the -10 and the -24 manuals. I have admittedly not read both in their entirety. I think your answers to both this post and my other thread show that I should! (and I will). I saw your thread on the interpreting and understanding the -10 manual, I've printed it and placed it with my -10 manual, but haven't read that in its entirety either.

Well, it would be nice to know what did go wrong with the A-7. Its a shame that it was coded PAOZZ. That way it always got tossed in the trash, when it was bad, instead of going back to the military to be looked at. I understand why, the part just didnt cost much, and shipping, handling, inspection, storage and paying someone to take it apart and find the bad component, just wasn't worth the effort. But still....................................

Agreed! I would LOVE to be able to troubleshoot it and I may still one of these days. I'm going to keep the part on my bench and pick it back up after I get the 803A situated on the pad out back and wired up. I'll report back if I find anything. As I mentioned before, the only thing that seems out of place is the white powder on the large green capacitor.

I got a quote back from Lisa Nash at Patco Electronics, a Southwire company. She quoted $357 for a replacement A7. My hunch on the $40 digital gauge is looking better now .

 

[Guyfang]

You didnt mention TM 9-6115-642-24P. So I am going to assume, something that never fails to get me in trouble, but assume you did not look it up in the parts manual. You took your information directly off the A-7. That's good. AND that's bad. Good, because you can kinda ID the component. Bad, because the parts TM, always has the latest NSN and part number. And you did notice, the A-7 had several part numbers. Which one, is the one you need? What if the part in your hand had been withdrawn from the supply system, because it had some sort of defect? The superseded part number and NSN are no longer good. You will never know about it, because you haven't looked it up in the book. Both part numbers would have given you the right NSN, if you look them up in FEDLOG, (We will get to that later) but only one of the part numbers, (19260) is listed in the parts book.

Also Bad, is that that part in your hand is one of the few parts in your gen set that has an UOC, (Usable On Code) listed next to it in the TM. But you don't know that, because you didnt look it up in the TM. What is a UOC? The TM's were written for several different model gen sets. One puts out 60 hertz, and one, 400 hertz. If you look at the TM, you will find TWO Freq transducers listed. Well which one do you need? Should you read the introduction and explanation in the front of the book, you would know what a UOC is, and which code is for the gen set you have. It is not uncommon, that someone orders a 400 hertz part due to not getting smart on the -24P, puts it in a 60 hertz machine, and wala! Nothing works. And because he put in a "new" part, why that cant be the problem. So it's something else, right? The end of a long story is that you troubleshoot till your eyeballs fall out, and cant find the problem. So it best to always have the latest TM's, and know how to use them.

Now, after looking up the part in the -24P, and finding it, you notice, no NSN. The best way to locate a part is the NSN. Most parts, when typed into your browser, will come up in a web search. But the NSN is not listed in the book! We're screwed. No. We are not screwed. Because, if you also read the rest of the instructions and explanations in the front of the TM, you would have found out the in SECTION IV, at the rear of the TM, there is a Cross reference listing. It starts with NSN's. In numerical order. It tells you where to look in the explosion diagrams, (figure and Item number) for the listed part, by NSN. Great stuff! If you have part in the hand, and don't know where it goes, look it up! Easy!! Way too easy. But this doesn't help you, because you have no NSN. So go farther in the SECTION IV, and you come to part numbers. In alphanumerical order. And when you find the part number 19260, it has listed next to it, the NSN! And also, the figure number and Item number.

And that's how you find a NSN.

Simple, when you know how to use the book. I am, one of these days going to sit down and completely describe how to really use the -24P. This was only part of the explanation.