Author Topic: Microwave TWT  (Read 1240 times)

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Online coppercone2

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Re: Microwave TWT
« Reply #25 on: May 24, 2020, 05:38:16 pm »
I think the grid is used for gain control and AM modulation.


Look like the T184-20 relies on a preamplifier rather then actual control on the helix tube. More modern I guess.
« Last Edit: May 24, 2020, 05:50:44 pm by coppercone2 »
 

Offline Jay_Diddy_B

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Re: Microwave TWT
« Reply #26 on: May 24, 2020, 05:57:58 pm »
Hi,
Look at this diagram:

http://www.pa0ply.nl/articles/Varian/highvoltage.jpg

Remember that body is at ground potential.

The cathode and the filament are at -2kV to -4kV with respect to ground.

The power supplies must be sequenced up and sequenced down.

I believe that the Helix supply has to be very low ripple or it will modulate the RF output.

It is not easy to make a power supply for a TWT.

Regards,
Jay_Diddy_B

 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #27 on: May 24, 2020, 08:58:48 pm »
Hi,
I have this exact PCB, since It was scavanged from the instrument.
But i can't figure how to turn It on, since this PCB look the same, but the others (voltages section an Logic) are from a different revision
 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #28 on: May 24, 2020, 09:23:40 pm »
The squence should be

Filament, soft start, 5 Min to warm It up

Collector voltage

Catode voltage

Helix voltage

Gnd Is the body that Is also shorted with the helix 1ohm resistance


This Is what I found on this TWT, using the tp points in the schematic that you sent to me
 

Online coppercone2

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Re: Microwave TWT
« Reply #29 on: May 25, 2020, 01:14:55 am »
3000 v to gnd by 1ohm??

sounds a little broken. I think that tube had a flash over and died.

How could, 3000V+, be connected to chassis??

please be more clear, this is starting to sound like it can kill you.

Do you mean the helix supply, or the actual helix itself? (as in, the work coil), which I would say RFin to GND and RFout to GND since all the literature calls the helix the plate.

So you are calling the helix voltage the cathode voltage, the helix the helix, ? so its cathode supply now?

so anode, cathode, actual helix assembly. fucking boiler plate
« Last Edit: May 25, 2020, 04:31:36 am by coppercone2 »
 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #30 on: May 25, 2020, 04:30:52 am »
It's like in the link that you sent to me

https://lh3.googleusercontent.com/proxy/QfEbqLuuCSN12lfmz4eJZ4Zi9TGvdbr8Q-58uLK-e_skMRjRnvFTP0sWn1ewUyd9dxqtAf66czC-MmaVYmxi5djV

The helix supply Is in common with the chassis
 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #31 on: May 25, 2020, 04:32:29 am »
https://www.cpii.com/docs/related/19/OIMPCWTWT_Iss.pdf

Here also, the helix supply Is in common with the chassis
 

Online coppercone2

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Re: Microwave TWT
« Reply #32 on: May 25, 2020, 04:34:20 am »
you mean the cathode supply positive is connected to ground by 1 ohm, since the cathode connection voltage is negative?

is it the depressed or non depressed collector?
 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #33 on: May 25, 2020, 05:05:42 pm »
Yes
 

Offline NiaDebesis

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Re: Microwave TWT
« Reply #34 on: June 01, 2020, 05:51:14 am »
I am now starting to create the HV transformer.
I have found a massive E E core transformer.
It has 2 x 4 turrets and is 12cm long.
Don't have the datasheet of the core, but I know Is used to make actually hv Transformers.
The doubt Is, Is better to wound the coils on the opposite sides of the transformer, or to make a single coil in the middle with primary secondary and primary configuration, with the primarys in series, a sandwich coil.

 

Offline Gerhard_dk4xp

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Re: Microwave TWT
« Reply #35 on: June 01, 2020, 12:17:38 pm »
There was a switch mode power supply in DUBUS by CT1DMK.
IIRC it was presented at the EME meeting in Paris in 1998.
I have not tried it, but CT1DMK things are said to work.

http://www.dubus.org/
https://www.qsl.net/ct1dmk/tw_twt1.pdf


Cheers, Gerhard
« Last Edit: June 01, 2020, 12:19:59 pm by Gerhard_dk4xp »
 


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