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It's on a RC power switch.
GEP50N05

I'd guess it is a P channel MOSFET.

Mike.

Thanks Mike. I was given a jomar power switch but can't find and info on its wiring or usage. No listing on their site. I did find a phone # so I'll call them today. I was interested in how much current it could switch. I guessed a power FET but not the N or P. Makes sense the P in its number is an indicator. I'll update what I find out just to verify you're correct.

It's on a Jomar Power Switch.
I've sent jomar an email with pictures.

I found a rcm mag article from 1990 showing the address and exact phone # on the Jomar power switch back. The house at that address was sold in 2010. I assume the original Jomar had retired. It's now listed as Ems Jomar. My email with pictures was replied to with the statement it's not a Jomar product. I suspect this was 20 years ago but was lost to the newer current Ems Jomar product line?
In any case I found a similar DIY article and hope to give it life after being in a friends parts box for ? years.
I had hoped to determine the fets max rating but it too is hard to find info on.
If it works to lite a led I'll probably change out the FET for a known one.
I'm taking a break from the 90-100f days and sunscreen to play in the cool.
I also have a few Kraft series 1970 TXs I'd like to put in Frsky 2.4 to take a break from computer radios. No sub trims, no expo, no beeps, simple trim tabs, a firm heavy metal box to hold tight.
There're fun to pass around at the field for starting up stories about the gold old days of RC. I have one K SStick that really gets them going.
Well good old days after 1968. I'll need a single channel, reed, galloping ghost, and analog proportional if I want stories before 1968.
I do have a Heathkit 5ch single stick that very few have ever seen. Thin tall case layout. I've mentioned this before and was waiting for a rainy day to convert it. Loving in LA I've not had any rainy days in 2 years so I guess I'll have to rethink my schedule.
SM

Noticing the MOSFET appears to be switching the NEGATIVE power rail, I now think it is a N-channel MOSFET. Also, following the general numbering of many MOSFETs, and looking at a datasheet for a STP50N05, I reckon it is rated at 50V and 50A.

Mike.

Thanks even more now Mike. I saw many listings for FET but couldn't make out it's rating. The board uses a CD4013 and I found RC switch circuits using it.
I have enough info to try it out now.

I have built a couple RC switches using that IC. And I made my own optocoupler using 6 SMD red LEDs. 3 as emitters and 3 as receivers facing each other. This means that the receiver is completely isolated from the load power supply. The alternative is to put the optocoupler at the 4013 input, but It also works like this. It is a bit bulky though as I built it in strip board And my optocoupler is 3 or 4 times bigger than a normal one But It was a fun project and it flew on my tricopter switching the flashing lights. Now I have a brushed ESC and can control brightness.
That would be a fun project actually. A kind of ESC for LEDs. maybe with an ATTiny and a MOSFET

https://www.youtube.com/watch?v=sxtdh8L53yw

This one is working as a glow plug driver:

https://www.youtube.com/watch?v=WC9EGoAlwA4

João

Thanks João. Good links. Is the M URD610CT a opto? I couldn't find that with google?

jhsa wrote:...Now I have a brushed ESC and can control brightness.
That would be a fun project actually. A kind of ESC for LEDs. maybe with an ATTiny and a MOSFET...

You mean something like this?
Works like a charm!

Klaus

That looks nice thanks, but the effects are pre programmed I think?
We can't even modify them because there is only the hex file, not the source code?
I would like to do the programming on the radio.

But lets not hijack this thread. I will open another thread on the electronics part of the forum

João