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Board for WA1GFZ MOSFET Audio Driver




 
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w9jsw
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« Reply #50 on: February 23, 2019, 08:06:45 PM »

Wow! Never was able to hear you in the Midwest during this low solar cycle. Wow...
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w9jsw
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« Reply #51 on: February 23, 2019, 09:37:31 PM »


The FETs and sink barely get warm and I leave them keyed on all the time. (The 4-1000A modulator tubes get T/R keyed in the fil CT)

T

Tom,

Do you do anything with the audio into the driver? Or is your control entirely just cutting the HV to the mod tubes.

John
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K1JJ
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« Reply #52 on: February 23, 2019, 09:59:00 PM »

Tom,
Do you do anything with the audio into the driver? Or is your control entirely just cutting the HV to the mod tubes.
John


John,

Partly.  I use the sequencer unit using time delay key contacts going into the one volt audio input of the MOSFET driver.  Last thing coming on and first thing turning off. No audio spikes or key up noise. I have many relays in the shack and two are very loud HV supply step start contactors, so I need to delay the audio until the very end of the sequence.  Without sequencer keying, the audio clack! is ridiculous.

(I sequencer key the fil CT and the HV to the modulator tubes too, so three ways.)

The only other solution would be using vacuum relays which would cost a fortune to populate.

The reason you haven't heard me, I hate to say, is that I haven't been on the air for a few years... just testing here and there.  I'm focused solely on helping others build their rigs -  or I'm trading the Dow Index futures market. I'm a type A very focused person and have trouble spreading out my attention.  I'm hoping when these new rigs (like yours) get going, I will MAKE the time.

You will hear me. I run a 2-el delta loop at 190' beaming SW.     Calif is easy on 75M when the solar cycle is low.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #53 on: February 24, 2019, 09:27:02 AM »


This is a recording taken from on the air transmitted on 3885 and received thru an R-390 at Jeff/ W2NBC's QTH.  


That sounds incredible, just like a PWMod rig, (sorry). Hard to believe you did that with tubes running linear.  Very well done.

73s Nigel
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A "Tube Free" zone.
w9jsw
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« Reply #54 on: February 24, 2019, 02:35:33 PM »

Updates

* Design Notes - 20190224-1.pdf (3020.27 KB - downloaded 75 times.)
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w9jsw
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« Reply #55 on: March 12, 2019, 11:27:23 AM »

Boards arriving today. Will send them out asap and will send an individual message when on the way.

Extra boards available.
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« Reply #56 on: March 12, 2019, 11:50:21 AM »

thanks John,

is there a final BOM ?
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steve_qix
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Bap!


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« Reply #57 on: March 12, 2019, 04:12:50 PM »

I've layed out a LOT of boards.  Your price is definitely in-line, particularly for the low volume.

When I order boards for the class E PWM modulators, I tend to get at least 40 at a time to keep the price down.  So far, all that I've made have been sold.  I think I'm on my 5th run at this point.

What size is the board that you're having made and where did you finally go to have it done ?

I have used ExpressPCB for everything so far.  Good quality, but I think they're higher in cost than perhaps is out there.

Regards, Steve
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High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
w9jsw
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« Reply #58 on: March 13, 2019, 06:02:07 AM »

Hi Steve,

The board is approximately 133mmx171mm. I used Precision Technologies or eproto.com. I did my layout on EasyEDA. I also use Elecrow for boards if I want to go to China Fab.

They had a $100 setup charge then a sliding scale based on number of boards and fab time. I chose my number based on how many solid orders I had at the time, a few more to sell to late comers and free ones to Frank and Tom for the immense help provided during layout. I also did not want to tie up my money on a huge order with doubts on if I would sell them all.

I then set my price accordingly. Won't get rich for sure but maybe $2 an hour wage for my time if I happen to sell all of them. But hey, when does a hobby ever break even?

John


* Final Boards.JPG (553.83 KB, 3264x2448 - viewed 117 times.)
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w9jsw
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« Reply #59 on: March 13, 2019, 06:50:08 AM »

Boards packed and shipping today. Here is the BOM.

WA1GFZ
K1JJ
KD6VXI
KC2ZFA
W1RKW
W8KHK
KB2WIG
W2WM
KC9LKE
W2XR
KA1SHU

Pending payment - WD5JKO

If I missed anyone, let me know...I tried to keep good records.

John

* BOM_WA1GFZ Mosfet Audio Driver.xls (11 KB - downloaded 51 times.)
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W1RKW
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« Reply #60 on: March 13, 2019, 04:07:52 PM »

John,
Thank you for your work and sharing.
Looking forward to starting a new phase for my 813 rig.
Bob
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Bob
W1RKW
Home of GORT. A buddy of mine named the 813 rig GORT.
His fear was when I turned it on for the first time life on earth would come to a stand still.
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« Reply #61 on: March 13, 2019, 08:20:12 PM »

I hear that there are some questions on how to mount the fets. I will work on that over the next few days. I don't yet have some of the larger FETs but i think I can show you using TO-220 fets and you will be able to figure it out. Here is a non-pic overview...

First step is to lay the board on the heat sink, and spot the six holes for the mounts. Once they are tapped or drilled, then you can mount it and spot the FET holes. If you are a good machinist, you can spot them all at the same time. I am not.

The FETs are mounted under the board, with the tabs flush to the heat sink. Don't forget silpads and insulators for the screws. Approx 18mm away from the hole, you bend the wires up 90 degrees. Then you poke them thru the board and bend them slightly. Then mount the board on the sink. You should see the fets thru the large holes. Screw them down. Then wiggle the pins to reduce stress on them and solder the 3 pins on the board.

From then on, you can take the screws out, remove the board, and remount it and it will fit just right.

Frank thinks 1/2 in or 3/8 in nylon spacers. I prefer 3/8 bit I don't have any fets to look at right now to see which one is best. The spacers should be available at any good hardware store.

John
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K1JJ
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« Reply #62 on: March 13, 2019, 10:44:22 PM »

Heathkit would be proud.  When stuffed, it will look as good as any commercial board.

Nice job, John!

I see Bruce, W2XR is building one too.   His 4-400A rig is one of the great sounding ones and I'm looking forward to him dropping the tube driver and pimping it out.

Yeah that's the ticket - everybody be pimping out their rigs!

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
w9jsw
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« Reply #63 on: March 14, 2019, 06:24:21 AM »

7 boards left. $35 each includes shipping to lower 48.
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w9jsw
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« Reply #64 on: March 14, 2019, 01:23:50 PM »

5 boards left.

Since most of the purchasers are from the east of the country, I think we can safely say that we are “Redefining East Coast Sound”!

Right, Tom?
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w9jsw
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« Reply #65 on: March 14, 2019, 02:47:59 PM »

3 boards left
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« Reply #66 on: March 14, 2019, 04:20:59 PM »

They are going fast!  To the west coast or east???   If I didn't know better, I would think your name was Bill Cullen "The Price is Right"!  How many of us remember him?

Good job, and thanks for making these available. I have always  wanted to try the WA1GFZ driver circuit, but I did not want to wire point-to-point.  This should make a very professional looking implementation!
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Rick / W8KHK  ex WB2HKX, WB4GNR
K1JJ
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« Reply #67 on: March 14, 2019, 04:24:00 PM »

5 boards left.

Since most of the purchasers are from the east of the country, I think we can safely say that we are “Redefining East Coast Sound”!

Right, Tom?


Wow, 3 left. They will go fast now that that's that on that!

Well, you might say we are doing our best to help out and point the way to better audio.  Cheesy    

A lot still depends on what the MOSFET board is driving. If a tube modulator has non-linearities and/or if the mod transformer is not of hi-fi quality, then we still have bottlenecks. At least we are removing SOME of the distorsion with a clean audio driver and overall NFB.

That said, I know of many big plate modulated rigs on the air that are built well and have high quality modulation components. They sound very good. Many use tube audio drivers with inter-stage transformers or 8 ohm hi-fi amplifiers driving backwards connected speaker/output transformers.  When these rigs receive the all-new, disco-duck GFZ driver board with audio negative feedback, they will sound even better.  Perhaps cleanly pass 50-100 Hz triangle waves that they could not before...  AND generate a cleaner signal on the air!
(lower IMD)

Over the next few months I hope we hear at least  1/2 of these boards on the air.   I'm sure there will be plenty of questions and optimizing work going on - here on the AM BB.

These group projects are the best!

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
w9jsw
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« Reply #68 on: March 14, 2019, 10:18:08 PM »

1 board left
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K6IC
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« Reply #69 on: March 14, 2019, 11:16:07 PM »

John,   Thank you very much for laying out this board,   getting it fabbed,   shipped,  and for sharing your efforts to this AM community.

Thanks,  too,   to GFZ Frank,   JJ Tom,  and all of the others who contributed to getting this project designed and built.

This is eggziting !

73,  THANKS,    Vic
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w9jsw
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« Reply #70 on: March 15, 2019, 06:43:32 AM »

All boards sold, pending payment....

Here is a datasheet on the fuses. Tom says 100ma is normal for his rig. The actual value you use depends on the tube that the board is driving.

John

* Littelfuse_Fuse_201P_Datasheet.pdf.pdf (583.95 KB - downloaded 40 times.)
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« Reply #71 on: March 15, 2019, 09:15:06 PM »

Now that we are officially into the construction phase, it's time to move on:

Taken from the board notes posted in this thread by John, the voltages on the MOSFETS below will give you a good idea if the board is operating correctly.

Connect two resistor loads to simulate the tube grids.  (Set the bias to -5 volts as the 300 volts is reached.)

When first built and tested, bring up the -+ 300VDC very slowly.  Sample the individual MOSFET voltage points below to make sure they are roughly tracking the 300VDC.  Once up to 300 VDC these voltage readings should be close.

Do a touchy-feely of all parts to be sure nothing is overheating. Be sure to respect the +- 300V supply when feeling around. Remember that - + 300V = 600 VDC when across them both.

Run some audio tones thru.  20 HZ triangles are a tough test and should easily pass.  Make sure everything is FB before hooking up the modulator tube grids.  

** As stated below, when connected to the real tube grids, be careful not to fry them since this is a low source impedance driver.  Be careful when applying negative feedback and the potential for the modulator and driver board to take off in audio oscillation when the NFB is overdone.  After 10 years of actual use with the prototype hand-wired version, I have never blown a grid fuse nor fried any grids.

The first person (guinea pig) to get one going should post his results since these boards have not been tested yet. You may be able to save others some time.   Wink

Refer to the notes for more details.

Thanks.

T



Additional info and WARNING:

“My design was modeled after the Gates quad 807 audio driver. The fifth stage was because Tom wanted a stage referenced to ground to make feedback easier. The 11N90 source impedance is a lot lower than an 807 cathode follower so you have to be careful not to fry the tube grids.”  

[The grid fuses will help if they are "fast-blo" and are sized right]


Frank / WA1GFZ:

Troubleshooting and pre test data - I recorded the operating voltages at each FET in simulation. This is assuming the output bias is set at -5 volts and the power supply is +/- 300 VDC.

M1: Gate = -.47 (set by bias pot ), Drain= +295.7, Source = -4.92

M2: Gate = -.47 (set by bias pot) , Drain +295.7, Source = -4.92

M3: Gate == -157.3, Drain = +160.7, Source = -161.7

M4: Gate = +5.86,  Drain = +135, Source = +1.5

M5: Gate = -292, Drain = -53, Source -296
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
w9jsw
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« Reply #72 on: March 16, 2019, 08:25:30 AM »

Boards packed and shipping today. Here is the BOM.

WA1GFZ
K1JJ
KD6VXI
KC2ZFA
W1RKW
W8KHK
KB2WIG
W2WM
KC9LKE
W2XR
KA1SHU

Pending payment - WD5JKO

If I missed anyone, let me know...I tried to keep good records.

John

For this first shipment, you will either receive them today or got them yesterday. Please post your build progress!

Let me know if there were any issues with packaging. This is the first time I have tried the Mylar packing envelopes. They seem to be always good with stuff I get from China so decided to give them a try on boards.

A second shipment of 3 packs of 2 boards each went out on Friday for K3YA, W3GMS and KC9LKE. Should get them on Monday.

John
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« Reply #73 on: March 16, 2019, 10:54:20 AM »

Thanks John!

Joe-W3GMS
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« Reply #74 on: March 16, 2019, 11:10:00 AM »

has the schematic implemented by the board been posted ?

a silly question: can the BOM, as posted above, be uploaded
to a parts vendor ?
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