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New amp fired up for the first time. 3cx3000A7




 
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Author Topic: New amp fired up for the first time. 3cx3000A7  (Read 2552 times)
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KD6VXI
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« Reply #25 on: March 16, 2017, 11:45:50 PM »

With the proliferation of projects, I'm contemplating the brake, shear, etc for 4 hundred at Harbor Freight.  It's harbor freight, but that sure would make a LOT of strap out of copper sheet!  :-)

I know about cool amp silver rub, used it on a couple tanks before.

My initial reason for braid was multiple.  I wanted flexible, so when things expanded and contracted things wouldn't break or be stressed.  And the original vac cap on CTune was too large, so I was hoping for a bit more inductance.  What I didn't take into account was, all those micro edges between each piece of braid, etc. As you and 'www explained.  Thanks, now I have an understanding of WHY it's bad juju.

The Q is designed at 6......  Another reason CTune had to be so small.  An exciter with predistortion  will be used, with the final pa wrapped into it) so the slight increase in imd wasn't too much of an issue.

When I pull the deck again, I'll take pics, but I used 1/4 inch copper tubing from CLoad to the output relay. It supports the back end of the vac variable.  Punched a 3/4 inch hole and routed top to bottom of chassis.

Got ya on the ceramic post to unload the rear of the vac variable on CTune. I was wondering about a piece of strap bent into a U to somewhat support the rear of the cap? As stated earlier, CLoad is supported front and rear.  CTune only by 3 stand offs on the front.  That seal carries a bit of weight now that you brought it up. 


YES the air filter mesh is intact.  I am thinking of a new home AC air return folded filter in front of it. Other than as a spectator on a bunch of mountain top sites, I've no experience with this type of operation...  The owner has done some repeaters....  I'm leaving the wherewithal of getting cooling  etc. Up to him.  I've increased the blower size.  More air means more cooling, but more dust too.

Wish the service panel was bigger here.  I've got a hundred amp service with a 90 amp feed to the shop.  I'm moving the meter main to the rear of my shop, which will drop my service drop about a hundred feet.  At the same time, I'm upgrading to 200A service so the house will get the 90 amp breaker instead of the shop lol.  Priorities!

--Shane
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KD6VXI
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« Reply #26 on: March 23, 2017, 10:09:12 PM »

Lesson learned about the braid.

Strap came in today, sheared it down and replaced the braid in the tank.

The piece from tube to CBlock had discolored.. The high impedance node from CBlock to CTune was fine, but from the end of the tank coil to CLoad was also discolored presumably from heat / current.

Still waiting on the new cap for the underside / Tuned input. Hopefully this doesn't change the tank much, I'm happy with the coverage.

--Shane
KD6VXI


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w1vtp
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« Reply #27 on: March 23, 2017, 10:38:04 PM »

My California Kilowatt.  IOW, let's make legal limit AM.

Well, almost done.  Did a test fire today  no fires or smoke except into the dummy load!

Power supply is Pete Dahl (new, not original) 4kv 3A CCS xformer, cap input with A FWB of K2AW diodes.

Has 242 volts on standby, 230 volts full power.    As such, it's 7.5 volts on the filament standby and 7 under fire.

I don't think I need the extra emissions of the half volt....

Pics speak for themselves.  I was able to keep the pep value all the way down to a 250 Watt carrier with my assymetry board, but if you don't have a sync detector  or sdr....

--Shane
KD6VXI

Suggestion: move your light source off to one side so the glare from it won't make the meter unreadable

Al
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KD6VXI
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« Reply #28 on: March 23, 2017, 10:51:53 PM »

Yeah, I need to experiment with the lighting.

I just installed a bunch of led shop lights and now it's so bright taking pics is hard.  I may put switches in so I can not light certain areas.  I already did over my primary operating area.

--Shane
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KD6VXI
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« Reply #29 on: March 24, 2017, 08:44:34 PM »

I thought he was going with an ANAN 10 for the exciter  and an 8930 as the driver  in close to  or in class A.

Today, this arrived to set up with the amplifier.  As well as the K3S.

I almost prefer the ANAN so as to be able to wrap predistortion around it, but we will see how this combo fairs......

--Shane
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KD6VXI
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« Reply #30 on: May 01, 2017, 08:05:54 PM »

Got the new capacitors for the tuned input from the past commies.  Wow.  Silver plated, welded plates.  I mean, there has to be as much silver on the caps as what I paid for them!

Anyway, created a couple stress tests.  On the RUSH video, about 3:45 or so, I pan around to the front display and the driver.

The mineral oil was BARELY warm to the touch, but honestly after almost ten minutes of CCS music oil boiling, I don't blame it.

For the RUSH fans:  https://youtu.be/bcViGUR6bS8

And if your a Wall of Voodoo fan, live in California, or otherwise understand the joke:  https://youtu.be/3SHU7G4v0aE  

Some people say the recordings are great, others that it's ragged.  It's a ten thousand Watt bird slug.  

And, for those that say PL259s won't handle legal limit ish.....

Anyway......

--Shane
KD6VXI



(I wanted to record this in the sdrplay...  However, even at 250 watts the sdrplay was full signal.  This was with a clip lead shorting the sma to so239 in a loop or with it using  the same clip to short the antenna input.  I also turned the LNA down as far as possible in HDSDR but that didn't do much, still fully to the right.  Any ideas?  I tried a couple times, since the recording on this cell sounds like a CB radio raped a telephone)

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KB2WIG
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« Reply #31 on: May 01, 2017, 08:11:19 PM »



Wrap it in foil Huh? ??

klc
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KD6VXI
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« Reply #32 on: May 01, 2017, 08:13:14 PM »

I wondered.  There is a guy on ebay selling metallic cases.  Before dropping the money, wanted to see if I could get any real whirl input on real shielding.

I mean, it couldn't HURT.   The rx is in plasdick now.

--Shane
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w1vtp
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« Reply #33 on: May 01, 2017, 11:18:24 PM »

[...snip...]





(I wanted to record this in the sdrplay...  However, even at 250 watts the sdrplay was full signal.  This was with a clip lead shorting the sma to so239 in a loop or with it using  the same clip to short the antenna input.  I also turned the LNA down as far as possible in HDSDR but that didn't do much, still fully to the right.  Any ideas?  I tried a couple times, since the recording on this cell sounds like a CB radio raped a telephone)



There's an accessory that does a perfect job of sampling high power.  It's a Coaxial Dynamics 7999 sampler. It gives you roughly 40 dB of attenuation which you can further reduce with something like a KAY step attenuator to get the signal just right.  The price is a little under $200 but well worth the investment - you'll have it the rest of your life.  I have a setup where I can with the sampler (in my case a Bird 4273) along with 90 dB of attenuation connect directly to my receiver.

You can buy these used for around $125 at RF Martin Supply, I think
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KD6VXI
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« Reply #34 on: May 02, 2017, 12:02:24 AM »

Al,

I get front end overload with the antenna connector shorted.

Would a sampler actually cut that down?

I was looking to purchase one about the time I got an ANAN, but if that will help this problem.....

I've already added common mode chokes to the USB line.  Maybe I need more, as well as an aluminum enclosure?

The pc speakers hooked up to the computer that was feeding the audio had barely discernable rf ingress.  Not bad, they shared the chassis ground.

The speakers on the bench pc I had to turn off.  Those are older Altec Lansing, and the rf immune where 39 bucks at wal mart.  My reason for bringing it up is, there's not THAT much residual rf.  99 cent store 1/8 inch to rca 6 foot cable with little to no shielding, etc and no feedback problem.

The sdrplay was connected to USB only, and the ant input shorted.

--Shane
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« Reply #35 on: May 02, 2017, 12:23:49 AM »

Shane,

I use the SDRplay for my station receiver, and you're right.  During TX, it totally gets wiped out.  It's not good for recording. 

What is great for recording is the REA modulation monitor.  In the software, it allows you to record sampled audio from the inline RF pickup into an audio file. 

I'll do my on-air transmitter experimenting for 75 meters around noon so that nobody can hear me and use the mod monitor for audio checks.

For the price, you can't beat it.  Oh, and it gives you your positive and negative peak percentages. 
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« Reply #36 on: May 02, 2017, 11:19:03 PM »

Sure is a nicely made amp. Compact as well. It's all about the plate transformer there, and no need for band switching.
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« Reply #37 on: May 02, 2017, 11:41:20 PM »

I have another one to start, going to be my personal amp.  A 3000 for 20 to 80 and an 8877 for 6 to 20, if all works out.  The owner is picking this one up in two weeks.  I can start mine finally!

Just as the maunder minimum is ready to set in.

--Shane
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« Reply #38 on: May 03, 2017, 07:56:27 PM »



Wrap it in foil Huh? ??

klc

Foil is so useful. Makes shields, pie plates, even hats! 


Shane, would you be so kind as to share the 0-40V variable bias circuit? All I can think of is a pass transistor as a bias regulator or a very stout DC supply in series with the cathode.
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« Reply #39 on: May 03, 2017, 08:41:55 PM »

I can, but it's basically W4ZT bias board. I also have 15 10A10 diodes that I can switch in the cathode return line.  The variable bias is also switchable.

When using the variable, I can go from 4 to 30 some volts.  The additional 10A10s take care of the rest.

The bias circuit has the ability to add additional in.  The bias board was an afterthought, so I left it as is.  

Taking son to Karate, I'll post the schematic when I get home.

--Shane
KD6VXI

Bah, have the Internet on the phone.

http://bias.gs35b.com/docs/060923.html

Link to entire page describing board, etc.
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« Reply #40 on: May 03, 2017, 11:22:35 PM »

I've used the W4ZT method also... really liked it on a single 3-500.. I have a stockpile of 50w zeners though, so I usually use the quickest method.
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« Reply #41 on: May 05, 2017, 01:16:36 AM »

Thank you!
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KD6VXI
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« Reply #42 on: May 05, 2017, 08:58:50 PM »

Patrick,  no problem.   

Jon,

I've ordered a metal case, purpose punched for the sdrplay.  I'll let ya know what, if any, decrease in stray rf I get.

I want to do some screen shots of the band with, but I can't see it yet myself!  Lol

--Shane
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« Reply #43 on: May 06, 2017, 09:21:43 AM »

Shane, have you tried it in class C? since you got that much bias. Anyway after investigation I think a different circuit may be better for me and allow keying via cutoff if the HV transients can be whipped. I'm still impressed with how nice your amp looks.
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KD6VXI
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« Reply #44 on: May 06, 2017, 11:03:59 AM »

Pat,

Thanks for the compliment on the amp. 

I have rolled the bias back as far as I can, but on the 6.4 kv DC tap, I still pull some plate current.  I'm going to go back to the 4.2kv DC tap and then I can get it in cut off.  On the high tap, I can only bring it do about 100 mils, iirc.

I have a chart I started at home of operating parameters vs bias.  It sure makes a hell of a difference in efficiency as you roll more bias on!

It also has a 10kohm cutoff resistor in the cathode circuit for cutoff on rx.

--Shane
KD6VXI
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