oh and speaking of smoke, no not that shit..these FETs are a PITA

The 50v disable board going into the brick, the controller board has a line directly to this to shut down for whatever reason, right now just high SWR, but the mica insulator behind it, or the shoulder washer didn’t like to stay insulated from ground. I suspect moving things around too much and the stiff wire going to the brick. after replacing this I put a fuse inline. It didn’t help those FETs today 🙁 and there was no error to disable. I need to make a high speed pulse detector to stop the power if it encounters an EMP lol

 

 

another smokey day

Well, the brick cooked 2 more FETs today, who knows. Power supply interference maybe I don’t know . also an input filter cap popped along the way, due to? cause of? who knows but i am looking at a better RF choke on the power supply line coming right into the amp. This pic shows whats there and what popped, it cooked a cap into pieces and there is only supposed to be 50vdc on it and no RF. well, I think maybe there is a ton of RF on it over 14mhz..so tomorrow I’ll try that direction. FETs replaced and re-biased. its working again but i’m not running it over ~50 out until I figure out how the smoke is getting out of these……FETs!!! I cleaned the board up, installed some 3.1kv .01 and a 6kv .001 cap in there. if that pops there is some serious shit going on in there!!!

 

 snap! Crackle POPferrite beads around the power lines coming in..maybe not helping?

 

FOLLOWUP —-

found out the caps they had in the kit were under rated. ah HA! a gotchya….

Hiding the filter board in back

I came to the conclusion to hide these in separate RF compartments (it didnt work as well as I thought it would) but its still this way. The filter board is in back, the brick in the middle and now the controller and Micro are in housings in the front, with filtering on all the leads. I used some Feed Thru caps and also those LC t devices. I have not powered it up again as the last time I was probing the controller RF hit it and opened the relays on back quick enough to pop 2 of the FETS and 2 stacks of 7.5 ohm 1w resistors. Its not bad I have spares I just don’t like letting the smoke out..

 

 feed thrus  filter LCtworking on the controller

More on the AMP…adding a few more pictures.

The last post was some pictures of what I did to eliminate the rf from getting in, its kind of interesting, tho it should work, not for any high speed work, the LC T parts cause some mutual pulse coupling if you run the leads close and you can see it in the adjacent leads..I noticed this when I setup the Micro to pulse the outputs so I could see if they were going to the correct pins and also the port was correct for selecting the filter relays, there are 6 filter groups on the filter board, when you select one group you have to deselect the rest and I was watching all the lines, the relays clicking don’t help as the de-energized clicks the same time as the energized so you cannot tell. here are some pics of more of the amp…enjoy!

 

Time to become one with the couch or grow a root as some folks say…

I spent a lot of time today on this beast again. Cleaning up this cabling mess. There is RF getting in everywhere over 14 mhz (20m Band in Ham-lingo) so I put the controller and the Micro , which is an Arduino Mega, in a shielded box..more on that later too. I’ll finish posting the 80 pictures I have taken and some other documents as time permits. Yea, no job I got time 🙂

As Shemp once said, “No wonder the water isn’t running , these pipes are full of wires!!!” well, we certainly have a few here.

The BRICK! yikes…it does weigh a lot, a lot of copper and a lot of Aluminum!

What your looking at here was the first thing we worked on, Peter KA1QEK found some copper and aluminum heat sink. He had a machinist friend work it out so they were connected pretty flat. Lots of hardware on top and underneath to hold it together, our concern was dissipating 1kw off this thing.  The fan would be moving air thru the bottom, I’ll post a picture later to show you the openings underneath it. I was still undecided at this point how I would mount it in my case i had gotten many years ago just for this project! I knew someday it would come in handy! Yea I tend to hold onto things! the FETS are the 250w SD2933’s, we got them as pulls.  You do need to test them first as some can get damaged, but all mine were fine.

//www.utm.edu/staff/leeb/mostest.htm

this works but instead of your finger, for these you will need to put the positive lead on it as you’ll need a higher voltage.

Believe me, this has been going on a year we will get into it later on how I know this , I cooked the first set last week (~52 weeks into this haha)