MEP-804B Over Voltage

[Sportsman02]

Hi all,

I'm in the process of building a shop and I'm using my MEP-804B single phased as a temporary power source until i can get everything hard wired into the local power company. Last Thursday, I went crank the generator and it immediately tripped the over voltage fault light and shut down the generator. After a couple of more tests and the same results I took off the voltage regulator (after reading several posts on here) and found my problem- a burned up transistor. It was a IRFP450 mosfet transistor installed in a TRC # 19870 voltage regulator. My question is, when looking for a replacement transistor i found several that have a different voltage and amp ratings. I ended up ordering a transistor that had a 500V/14amp rating, is this adequate? I was unsure how to find the exact specs of this transistor for comparison.

 

[kloppk]

The IRFP450 is spec'd at 500V and 14A. Looks like you probably ordered the right one.

What make and part number did you order?

To get the exact specs you'd need to determine what manufacturer made it. The specs vary slightly from manufacturer to manufacturer.
Usually there is a manufacturers logo on the device.
A good source for specs once you have manufacturer identified is DigiKey. They list parts, even obsolete ones like the IRFD450 with links to the datasheets.

 

[Sportsman02]

Thanks for the good information kloppk. Well, i ordered replacement transistors from a vendor off of a popular mega store and the seller listed themselves as a manufacture and their own part numbers. But, in the pictures it appears they are made by- Siliconix part number: IRFP450. If the pictures are correct from the mega store, this should be the same manufacture and the same part number from the one from voltage regulator. The only difference i see are the middle and bottom lines on the transistor with different letters and numbers. I should get the new transistors in tomorrow and i can compare first hand. If everything looks good, i plan on installing and seeing if this fixes my over voltage problem.

 

[kloppk]

... The only difference i see are the middle and bottom lines on the transistor with different letters and numbers....

Those likely are lot codes or date codes on the device which will vary.

 

[Sportsman02]

Ahh.... gottcha

 

[Sportsman02]

I got in the transistors yesterday and they turned out be the same manufacture and same part number as the original ones. I installed two IRFP450's into the board and put the voltage regulator back together and she fired up making the correct voltage. I was glad to see this happen.

I ran the generator a little over 3 hours yesterday evening with a 10% load the entire time- running lights, shop fans and the occasional use of a miter saw with no issues. I'm hoping this fixed the problem.