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Another 813 Build




 
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w9jsw
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« Reply #125 on: August 03, 2019, 02:16:28 PM »

Hi Tom,

You have convinced me - again.

I plan to use the same unit you used - ACS712, I believe. It puts out an analog signal with it at VCC/2 for zero current. How did you hook this up to the latching relay? Did you use a comparator circuit like is described in the application note that allows you to tune the current trip points? Since I am using a Arduino for my sequencer, I am really tempted to use one of the analog inputs and monitor the voltage directly. I can do this in a loop while I am in PTT mode. If I see any of the currents go past normal, I can shut off PTT directly. I have a small TFT display so I plan to also display the data digitally.

My only concern is what happens if the Arduino messes up. Using the Arduino is an untested approach as I don't see anyone else doing it. If RF scrambles it's brain I may lose the whole rig. So I am tempted to also have a failsafe discrete system that watches the same sensors and drags PTT low outside of the sequencer.

I just don't know...

On Spark gaps. I was planning on gaps on the mod secondary tap 4, the other side of the mod reactor secondary tap 5 and the 2 primary connections that go to the mod tube plates taps 1 and 3. Does that sound correct?

John
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K1JJ
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« Reply #126 on: August 03, 2019, 06:37:56 PM »

Hi John,

If you put everything in an aluminum box and then bypass the input leads with .001's (and toroids if needed) , there should be no RF in the circuit.

This six relay latching board below for $9.37 should work FB.

https://www.ebay.com/itm/6-channel-12V-latching-relay-module-Switch-controls-the-high-voltage-H-current/121951095953?hash=item1c64da0c91:g:oVYAAOSwAvJXCcQQ


It will take a low level signal to trigger.


A sensor like you suggested  below may work OK -  or some other derivation. These are only $3.95 so worth the try.  Order the six relay board and then see what sensor works best with it. Play around.

https://www.ebay.com/itm/30A-range-Current-Sensor-Module-ACS712-Module-Arduino-module-NEW/382824575626?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D57476%26meid%3Dec2b38a14a9541fd80c52ea43f41aaff%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D202681517336%26itm%3D382824575626%26pg%3D2047675&_trksid=p2047675.c100005.m1851

You can generally use a 0.5 to 2 ohm resistor in the negative DC lead for the grid, screen and plate to get a tiny DC current sample.  A pot across the resistor sampler can then adjust the trigger point. At least that's what I did here.  My particular current sampler has an opticoupler in it, but I cannot determine what kind it is due to no labeling of value on it.

I did not use a comparator, but that would work fine.

This really is a cool system once working. For example, I can tune my 4-1000A finals off resonace, drive it for too much grid current or load the final for more screen current and off goes the PTT. Even a bad antenna, forgetting to turn on the HV, etc etc, will trip it. Not to mention when I mess up and hit the audio too hard, the PTT drops out due to the modulator current(s) (grid, screen or plate).  I realize there is a slight delay due to using a relay and the PTT unlatching, but with tubes it is plenty fast enough without causing damage.  When the rig has been pretuned and turned on again, you don't even know the protecton circuit is there other than the trip lights are off.  When it trips, I know exactly what circuit (of six) tripped by the LED being lit. Just reset it and try again or adjust the current sensor a little until the rig runs flawlessly at normal parameters.

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."
K1JJ
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« Reply #127 on: August 03, 2019, 11:12:34 PM »


On Spark gaps. I was planning on gaps on the mod secondary tap 4, the other side of the mod reactor secondary tap 5 and the 2 primary connections that go to the mod tube plates taps 1 and 3. Does that sound correct?

John,

I think you have it, but just to be sure:    Four sets of gaps are used. Round ball gaps are best.  One set across pins 4-5 secondary.    One set across pins 3-2  primary.    One set across  pins 2-1 primary.    One set across the modulation reactor, L1.    I also put a small one across my screen choke as a precaution after having unkeying spark problems in general, but is probably not needed there.

Also remember that later on in testing if you have unkey sparking, a vacuum relay that puts a 5K 100 watt resistor across the mod reactor when unkeyed will quench the sparks. It solved all my sparking problems despite having a sequencing system.   No matter how we look at it, that energy stored in the mod choke has to go somewhere during shutdown and if it doesn't  eventually find its way out to the antenna in the form of RF, it will spark instead at the reactor. Bad sparking is what damages our iron in the form of internal insulation arc-overs.. (both mod xfmr and choke)   Normally commercial BC iron is safely turned on once a day or less. Hams beat the crap out of it with the rapid PTT. We gotta have it set up right or get your wallet out again.

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 #128 on: August 04, 2019, 07:41:03 PM »

Ian's (G3SEK) has a tetrode protection board that does exactly what you're looking for.

Schematics are freely available for the googling.  Would give ideas in pictures on what is being discussed.

--Shane
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w9jsw
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« Reply #129 on: August 06, 2019, 05:05:58 PM »

What about using either 1 or two of these to regulate the grid current to 80ma - IXCP10M90S
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K1JJ
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« Reply #130 on: August 06, 2019, 09:54:06 PM »

What about using either 1 or two of these to regulate the grid current to 80ma - IXCP10M90S


An interesting thought... using a solid state current regulator device to limit the maximum current thru the screen to 80 mA. It should be invisible until current hits >80 mA.

I've never tried a current regulator so not sure if it makes sense in this application.  Maybe one of the guys with circuit modeling software can simulate it. Make sure it will handle 500V X2 if it is referenced to ground...

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 #131 on: August 07, 2019, 05:48:20 AM »

Here is the article - http://amfone.net/Amforum/index.php?topic=30947.0

I am also looking closely at the tetrode board. It has a lot of really nice features...
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DMOD
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« Reply #132 on: August 09, 2019, 11:18:38 PM »


Quote
An interesting thought... using a solid state current regulator device to limit the maximum current thru the screen to 80 mA. It should be invisible until current hits >80 mA.

I've never tried a current regulator so not sure if it makes sense in this application.  Maybe one of the guys with circuit modeling software can simulate it. Make sure it will handle 500V X2 if it is referenced to ground...

Tom, were you thinking of something like this?

R3 senses the Isg current and develops a voltage drop which switches Q1 on and startes to pull down the gate voltage. One trims R3 for the threshold sensitivity and current limit.


Phil - ACC0OB

* Regulator FET with Current Limit.pdf (106.87 KB - downloaded 34 times.)
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w9jsw
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« Reply #133 on: August 12, 2019, 06:57:39 AM »

thanks Phil. I will breadboard this soon. Since it is very close to the regulator you designed for the mosfet board, I am going to take one of those PCBs to build it. With a few jumpers and some extra holes for the 2N3904 I think it will fit up nice.

I think I will scrap the 75V bias design using the VR tube as well and build up another regulator board for the -75V.

Thinking about all of the PCBs and silicon on this transmitter I think I have an idea for what I will call it. With these 2, the 2 for the mosfet board, the mosfet board itself, the RF driver that will be silicon based, the sequencer that will be an arduino with relay board -  it is adding up.

The name is The Borg...

If you are familiar with the Star Trek canon, this makes sense. Take technology from other species and craft it into a new being that is technologically superior to the prior beings. With the amount of silicon crafted on to a hollow state design it kind of makes sense, I hope...  Grin

John
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« Reply #134 on: August 12, 2019, 05:43:12 PM »



"     If you are familiar with the Star Trek canon  ... "
   

I worry about these 'hybrids'. You never know what they'll do.....   As Capt. Kirk would say, " whose your daddy, Nomad? "

klc
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DMOD
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« Reply #135 on: August 12, 2019, 07:45:52 PM »

thanks Phil. I will breadboard this soon. Since it is very close to the regulator you designed for the mosfet board, I am going to take one of those PCBs to build it. With a few jumpers and some extra holes for the 2N3904 I think it will fit up nice.

I think I will scrap the 75V bias design using the VR tube as well and build up another regulator board for the -75V.

Thinking about all of the PCBs and silicon on this transmitter I think I have an idea for what I will call it. With these 2, the 2 for the mosfet board, the mosfet board itself, the RF driver that will be silicon based, the sequencer that will be an arduino with relay board -  it is adding up.

The name is The Borg...

If you are familiar with the Star Trek canon, this makes sense. Take technology from other species and craft it into a new being that is technologically superior to the prior beings. With the amount of silicon crafted on to a hollow state design it kind of makes sense, I hope...  Grin

John


Or, how about "GLASSFET?"   Grin  The Borg is not only exhilarating but also assimilating! Cool


Phil
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w9jsw
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« Reply #136 on: September 22, 2019, 07:16:43 PM »

Still plugging along. Mostly mechanical work...

First chassis is in place - power control. Will start mounting low voltage stuff as soon as the HV is done. Probably have around 2 hours more on the HV to complete it. Still spending a lot of time outside and not in the shack. Hopefully this will start to move more once the nasty weather starts.

John


* IMG_0313.JPG (117.35 KB, 568x757 - viewed 72 times.)
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K8DI
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« Reply #137 on: September 24, 2019, 09:23:37 AM »

First chassis is in place - power control.

John, I see the picture, and the chassis. Have you considered using stuff like this for chassis instead? To me, while it is a commercial product, it is neater and screws right to the rack rails like it should.


https://www.middleatlantic.com/products/accessories/rackmount-storage/chassis/ch2.aspx




https://www.middleatlantic.com/products/accessories/rackmount-storage/chassis/ch3.aspx



Big giant caveat:  my company is a dealer for this product. But I am happy to sell to anyone with a callsign for 5% over cost, plus shipping. And, I have been using them in my own projects for years -- these and their economy models (all steel, not as deep).

Ed

Note to mods: if this is inappropriate, please delete and let me know.
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Ed, K8DI, warming the air with RF, and working on lighting the shack with thoriated tungsten and mercury vapor...
w9jsw
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« Reply #138 on: September 25, 2019, 06:39:19 AM »

Thanks for the info, but I like the direction I am already taking. Plus I already bought what I need.
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« Reply #139 on: September 26, 2019, 03:33:22 PM »

Looking good, John.

Suggestion: mount your power resistor(s) vertically for better convection cooling.
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Bob
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w9jsw
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« Reply #140 on: September 26, 2019, 08:23:15 PM »

Thanks. Been trying to decide where to put them.
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« Reply #141 on: September 26, 2019, 10:44:33 PM »

Good use of the sides of the rack though.
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w9jsw
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« Reply #142 on: September 28, 2019, 02:30:53 PM »

ok, hope to fire up the HV tomorrow. Please offer advice so that I do not fail to cover an aspect of this bringup. This is the plan of attack.

I have a 4 wire panel using a ganged breaker feeding a properly grounded 4 wire cable into the frame.

I plan to bring this up in stages.  

The old iron I will be using is a Gates transformer and matching swinging choke, into 64mfd of oil filled caps. The only load will be the 100K bleeder. I will be using a 24V separate supply for the control voltage to the main HV relay2.

I will have a validated HV meter across the bleeder that is connected such that I don't have to probe it. I will not be touching anything in or near the frame while under power. The HV will not be connected to anything beyond the bleeder at this point.

Referring to the schematic - I plan to first disconnect the output side of the circuit breakers and connect the VOM across those open contacts to monitor 240V.  I should then be able to test the RLY1 fail-safe part of the circuit to insure that it actuates the relay when on then off. Also will cycle the breaker to see if it drops but does not restart the power.

Then I will shut off the breaker and unplug the unit. I will reconnect the output 240v from the CB to the Relay2. Will set the rheostat to minimum. Will plug the unit back in and activate the breaker. Will press the ON with a wooden stick. Hopefully no smoke and I will hear nothing. Then actuate the 24V HV control. I should hear a click of that relay, then shortly thereafter a click of the softstart RELAY9 and see some indication of HV on the external meter. Since my internal meter will not be calibrated, hoping for some deflection there.

If I hear no softstart, shut down the main power and the breaker. Then advance the rheostat to close to mid point. Try again. At some point I should see some HV. Alternatively, I could install the Rheostat bypass and bypass that part to prove the softstart works with normal 240V.

Now what? The trans and choke are insulated on the mounting platform board. How do I check for leakage to the frame safely?

At some point, I should be able to convince myself that all is working, and I should be able to then safely calibrate the internal HV meter. I will do this very methodically such that I am sure there is no HV in the rack when I reach in to turn the pot on the back of the meter.

Hopefully this all goes well and we get a solid 2500V out of the bringup.

John

* 813 Transmitter.pdf (185.53 KB - downloaded 12 times.)
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K8DI
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« Reply #143 on: September 28, 2019, 02:37:40 PM »

John, if you have the means to do so, sub in an undersized/smaller main breaker while you do this...something that will blow if something’s wrong before enough current flows to break parts.

Also consider hanging some lamps on various points to verify you have 240 and 24 as you power up.

Ed Walters
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w9jsw
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« Reply #144 on: September 28, 2019, 02:43:22 PM »

This is a 30A circuit. I was planing to use a 20A to start. Should I go to 15A?

24V is coming from a cheap switcher supply that I purchased and has it's own power LED. I will be able to test the actuation of the HV relay with everything else off.

The main switch has a built-in 240V light that is wired after the CB. Not shown on the schematic. I will place a second VOM across the trans primary to see that 120-240 voltage. Don't have any 240V lights. Good suggestion.

Thanks for the ideas.

John

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« Reply #145 on: September 28, 2019, 04:46:16 PM »

John,

You could follow Phill KA4KOE's example of when he powered up his BC1-T for the first time.

https://youtu.be/fpnKwQVJN5A

Having someone away from close proximity to the rig with access to the power plug would be a good idea.

I remember once when I had an AM KW, one time the PTT relay fused together while the plate current meter was pegged, and final tubes putting an orange glow on the ceiling. I had to run through the house, into the garage, and flip the breaker! Problem was, I had push pull cross neutralized triodes. The neutralizing caps at the feedthrough null were too close together. I got this really bad idea to add 3" diameter Weston meter glass between the neutralizing cap plates. The setup null with just drive was perfect! When I keyed the B+, I darn near burned the house down...The glass shattered into a million pieces.  Cry

Jim
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* Backup_Buddy.jpg (106.9 KB, 977x570 - viewed 45 times.)
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w9jsw
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« Reply #146 on: September 29, 2019, 07:48:51 AM »

Watching the video - a fire extinguisher seems like a good idea!

On the floating iron - should I ground the frames of the trans and choke and only float the modulator and mod reactor?

For this test, I think I will ground the frames. That way if there is a winding failure it should take out the breaker hopefully without a lot of smoke?
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« Reply #147 on: October 02, 2019, 01:30:01 AM »

If by 4-wire breaker you mean you will break the electrical ground, I believe that is unsafe.
How about keeping a solid ground from the mains GND to the chassis and just breaking L1-N-L2?
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w9jsw
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« Reply #148 on: October 02, 2019, 06:30:17 AM »

A 4 wire panel with separate G and N. Breaker cuts off L1 and L2.
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