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4-400 noise




 
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Author Topic: 4-400 noise  (Read 1328 times)
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Detroit47
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« on: January 24, 2018, 11:17:01 AM »

Hi all

I have a couple of 4-400's that look real nice and check out good with an ohm meter. There are no loose pieces floating around inside the glass. My concern is that if I turn the tube over end over end I can hear movement inside the tube. Unless I am wrong there should be zero noise. Being that the grid and screen are supposed to be totally rigid. I was hoping to use them in my 500 but me thinks this may be a bad idea. If so I must find a new 4-400. I think that mine may be a little low. So what do you folks think about the noise.

John N8QPC
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« Reply #1 on: January 24, 2018, 01:52:14 PM »

I think that if you hook up a VOM and set it on the lowest scale and turn on the tone signal you then could clip leads from the filament, and to all other elements in the tube one at a time, then turn it over, gently bang on the side and do everything possible in gyrating in every possible position, maybe stand on your head? If you don't hear any beeps from the meter, it's probably ok. When the tube is at operating temperature, it may have taken up the slack and perhaps there would be no loose parts sound if you could test it when its really hot? In operation, the first thing I would look for is the grid current meter going off scale in the negative direction indicating a control grid to filament short.

Bad things can happen really fast in a tetrode to the associated circuitry, so you need to have your settings rehearsed before you hit the big switch! I hope this helps you qualify the tubes Grin Grin
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WD8KDG
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« Reply #2 on: January 24, 2018, 02:18:50 PM »

Had a few 4-250's a while back, might of been 4-125's. Anyway tapping on the glass I heard a sound that was not good. Placing the clip leads of a VOM onto the pins told the tale. Shorts

Long ago someone told me to always store the toobs standing upright, no sag of the elements.

Gud Luck with the noise,
Craig
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Detroit47
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« Reply #3 on: January 24, 2018, 03:12:21 PM »

I checked it every which way with clip on leads on high scale of Simpson 260. I tapped it and turned it all around no deflection. I  took my adjustable bench supply and set it for 300vdc and went from grid to screen. as well as grid to cathode no current. I bitch slapped it a couple of times for good measure. I may just make up a test jig to go on my tv-7. I had one for my I-177 and I sold it. The old story I aint ever gonna need that. Duh. I am too chicken to just stick it in my rig I just got it running.

John
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WD8KDG
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« Reply #4 on: January 24, 2018, 04:02:38 PM »

Magic smoke drifting thru the shack is never good Grin

Craig,
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Jim, W5JO
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« Reply #5 on: January 24, 2018, 04:24:12 PM »

There is a company in Florida that will test them for you and provide performance figures.  Check for them on eBay.   If you plan to keep and use them a small investment to be sure of their condition is better than smoke from something in the transmitter.
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KC4VWU
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« Reply #6 on: January 25, 2018, 02:45:14 AM »

Yeah, don't roll them right into the tx. for testing. Ask me how I know. Should'a known better!

I ran across a nice pair of used Eimac 4-250's at Benson last year at a good price. Need to really get serious about lashing up a test circuit to go through what transmitting tubes that are here. I do try to store them upright, but just curious that if the specs say they can be operated in either vertical or horizontal (generally speaking), does it really matter during non-use periods?
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Detroit47
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« Reply #7 on: January 25, 2018, 01:31:42 PM »

Well I made up a little test jig. It filled with smoke as soon as I lit the filament. Turns out to be a gas bottle. I am glad I didn't just plug it in the rig. So I am on a quest for a 4-400.

John N8QPC
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« Reply #8 on: January 25, 2018, 02:25:09 PM »

Quote
Well I made up a little test jig. It filled with smoke as soon as I lit the filament. Turns out to be a gas bottle. I am glad I didn't just plug it in the rig. So I am on a quest for a 4-400.
  AW, a seal is broken! Just hook up an air hose to the plate cap and blow the smoke out! Good to go for another 500 hours Grin Grin Grin

As a side note, I wouldn't be afraid if I had a 500 to use a 4-250 in there in place of the 4-400. Lots of them around and usually less costly for them. I plan to use a pair of 4-250's in my Desk KW. I am not going to use it for side band so 500 watts of plate dissipation is more than enough for a 350 watt output power. Originally, the Desk KW was furnished with 4-250's. Per Eimacs spec's A 4-250 at 2500 vdc with 200 ma plate current will render 375 watts output. Another interesting tube that will plug and play is the PL-175 by Penta Labs or the 175A by Eimac will work, It is a pentode and the metal ring around the base must be grounded by those clips that are provided in the Desk KW. That ring is the suppressor grid. They are supposed to be a more efficient tube and will render more output with the same parameters. I am going to get my Desk going this summer and try the 4-250, 4-400 and the PL-175 and record the findings. Please stand by for the report...
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Detroit47
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« Reply #9 on: January 25, 2018, 03:12:00 PM »

On a side note since the tube is junk. I am going to open it up and look at the grid and screen structure. This should be interesting. I want to know where the noise came from. I will supply pics if there is an interest.

John N8QPC
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« Reply #10 on: January 25, 2018, 03:16:23 PM »

I would be interested in seeing the pictures. I would also like to know how you did the opening of the tube and not destroy the elements in the process. A couple nights ago I was reading about the very special glass they use to make hi power vacuum tubes. It might take a bit more of something to open one of those things?
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Detroit47
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« Reply #11 on: January 25, 2018, 03:46:16 PM »

I will try and cut it the same way I would cut a bottle or glass tube. I will score it with a glass cutter around the base, and tap it it should break clean. I could also score it and warm it with a candle along score. My other hobby is stained glass. I am sure that the glass is just corning glass. It has to have been annealed to take the heating and cooling.

John
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WD8KDG
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« Reply #12 on: January 25, 2018, 05:01:26 PM »

Quote
Well I made up a little test jig. It filled with smoke as soon as I lit the filament. Turns out to be a gas bottle. I am glad I didn't just plug it in the rig. So I am on a quest for a 4-400.
  AW, a seal is broken! Just hook up an air hose to the plate cap and blow the smoke out! Good to go for another 500 hours Grin Grin Grin

As a side note, I wouldn't be afraid if I had a 500 to use a 4-250 in there in place of the 4-400. Lots of them around and usually less costly for them. I plan to use a pair of 4-250's in my Desk KW. I am not going to use it for side band so 500 watts of plate dissipation is more than enough for a 350 watt output power. Originally, the Desk KW was furnished with 4-250's. Per Eimacs spec's A 4-250 at 2500 vdc with 200 ma plate current will render 375 watts output. Another interesting tube that will plug and play is the PL-175 by Penta Labs or the 175A by Eimac will work, It is a pentode and the metal ring around the base must be grounded by those clips that are provided in the Desk KW. That ring is the suppressor grid. They are supposed to be a more efficient tube and will render more output with the same parameters. I am going to get my Desk going this summer and try the 4-250, 4-400 and the PL-175 and record the findings. Please stand by for the report...


Unless one has a means to monitor the screen current on the Desk KW, consider using the recommended loading. Several bulletins were issued to original owners regarding this issue. Loading at recommended settings, low power will give about 225 watts output. Hi power is great for elbow room, 700 watts ++++. Grin Low power is more that enough for surrounding states and then some.

I use 4-400A's in the Junkston "500" sounds great last long time. The KW gets 4-250A's, been pick'en them up at fest for $10-$20 a toob. Pair of 4-250A's in the KW run at low power, toobs never break a sweat.

Craig,
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KD6VXI
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« Reply #13 on: January 25, 2018, 05:45:38 PM »

A piece of nichrome / toaster wire around the jug.  Use a variac to vary the voltage and the heat.  Makes a FINE bottle opener!

I've also got Dremel.diamond bits to do it with, but a piece of nichrome works fb.

I'd like to see the picks. 

--Shane
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WD8KDG
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« Reply #14 on: January 25, 2018, 09:18:55 PM »

Here is a link to the service bulletins that came with my Desk KW, link to BAMA

http://bama.edebris.com/manuals/johnson/deskkw/service

Enjoy,

Craig
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« Reply #15 on: January 26, 2018, 11:03:09 AM »


Quote
Here is a link to the service bulletins that came with my Desk KW, link to BAMA


Thanks Craig, I have owned the Desk KW for 12 years now and it would only take a few hours to get it going. At the rate I do things, I will need another 560 years to get my projects done! Some may take more than 1000 years. I'm kinda slow Cry Cry Cry
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