600W linear

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Sangoma
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Joined: Thu May 28, 2020 4:04 am
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600W linear

Unread post by Sangoma »

This is now set to be my next major project.

No doubt it will be a long one, as it will be built in basic form first, and completed on the go, ie manual band selection with automatic to follow, simple auto tuner, and better one with memories.

Sequencing and control will be logic, but protection circuits will be linear.

I have decided not to make it too small, it will be about 250W X 350D X 120H.
This will allow fairly quiet cooling for 400W on a 50% duty cycle, and 600W capability on a 30% duty cycle, which means it should handle 600W SSB all day :)

I think I will end up making a main board to handle the protection and power supply, a processor board to handle the sequencing, band selection and rig control, and of course another board for the tuner. The logic board and the tuner only need to communicate band data, which I will do with Yaesu 4 bit BCD

It will be fully automated with the FT-991, FT-817, X5105, IC-703 and the IC-7300.

It will have 3 antenna ports, 2 HF and one 6m/4m, though as yet I am not certain of the amplifiers performance on 4m, may be limited to 300W.

It will NOT have full break in for CW, absolutely no use to me :)

Two protection circuits; SWR, high input power, over current will cut the main power requiring a power cycle to reset, over temperature will cut all low voltage supply except the fans, meaning it will be re-enabled when the temperature comes down, and can't be reset.

I have started designing another tuner board, which will be stackable with the LPF board (bought as a kit, capacitors I need are on order and won't be here for months maybe, can't wait that long :) )

It is a lot more complex than the 1.2kW amps, so at the moment there seems a lot to do :)
Last edited by Sangoma on Tue Nov 17, 2020 6:32 am, edited 1 time in total.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: 600W linear

Unread post by Sangoma »

The tuner and LPF is complete, tuner work a dream, and the FL-7000 is totally happy with it on every band.
600t1.jpg
600t3.jpg


But, (there's always a but isn't there) after a few minutes of 550W carrier, the inductors and the inductor relays are getting quite warm, The air cored ones are nearly too hot to touch.

I've redesigned the board for bigger relays, and will have to up the wire to 1.5mm, I just hope I can fit the turns on the cores, and the inductors will fit between the relays. I don't want to make the board wider, as I want it to fit on the LPF as in the photo.

I'm quite surprised, as the 1kW one uses 1.5mm wire, and 16A relays, so I thought it would be fine at half the power.

The capacitors are fine, which is good, as they are not the ideal for RF, but the only 3kV ones I have.

So this morning, the new tuner looks like this :D
bits.jpg

Don't think I will get the board made for a couple of days.

Pity, but I want it right.
Will not pinch bits off the old one, can box it up one day and use it, will be fine for the legal limit.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: 600W linear

Unread post by Sangoma »

Board made, and the box of bits now a tuner board
600t4.jpg
Soldered the high current tracks to increase current to be on the safe side
600t5.jpg
Took a chance on using 0.6mm tracks, but the software and router did the job, despite the fact I used a blunt bit which I thought was new.

The wire is thicker on the toroids, and much thicker on the air cored inductors.
600t6.jpg
Made a couple of extra minor changes to the board just to tidy it up a bit, and to include improvements.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: 600W linear

Unread post by Sangoma »

So pleased with it, made the final control board with decent connectors.
600t7.jpg
I like it better than any commercial tuner I have or have had, wish it had been around earlier, would never buy a commercial one again :)

Now to get on with the linear protection circuits.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: 600W linear

Unread post by Sangoma »

Designed, built and tested the input protection, SWR protection, filter select protection and the 50V switch with three 12V supplies, one resettable..

Busy doing the board for the auto and manual filter selection.

All the above can be used on a 1.2kW amp if I decide to put it together. I have the amplifier modules, so may happen.

Quite different in many respects to how I did it before (that was using ready made boards).

Then it all the metal work, which takes as long as the rest of it.

No wonder linears are so expensive to buy !
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
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Re: 600W linear

Unread post by Sangoma »

Made all new boards this morning, still another 50V protection cut out, but waiting for a new device, but the original works fine.
Couple of the boards had minor changes I decided on after building the first ones.
ab.jpg
I see the amp module is in the post customs dispatch in Russia now, so should be here later in the month.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
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Re: 600W linear

Unread post by Sangoma »

Well the amp arrived today
amp2.jpg
12V power supply finished, input protection board finished, filter switch board (both auto and manual) finished and the high current 50V cutout finished.
12Vpsu.jpg
input.jpg
600bs2.jpg
50Vcut.jpg
And the tandem match that will go between the amp and filters, gives ALC for the TX and SWR for the high SWR protection circuit (which is in fact on the input protection board)
tandem.jpg

Now it is a case of making a mock up to get the exact case size, then ordering the aluminium, that is when the time consuming part starts.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: 600W linear

Unread post by Sangoma »

Now the slow part comes.

This morning drilled the copper heat spreader and drilled and tapped the heatsink.

All fits nicely, won't solder the mosfets in place yet.
au1.jpg
G 3 E J S
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