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triode vs tetrode

359 said:
I keep following links for cheap YC-156's and they aren't there, which is making my brain hurt even more :glare:
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I keep telling people this. Unless you have a source for good used thats reliable... these tubes are worthless to lust after. For all its merits it is still an odd ball tube with limited availability.

This is why I try to steer folks towards tubes that are readily available from a multitude of sources with warranties that have a future.

I hope you can build it though. It would be a fun project.
 
To bad you guys missed the YC-156 boat.

I bought a pile of them :D

If they ever dry up in my lifetime I'll look around for another large triode.

Of course that will never happen because I dont beat my stuff to death.
 
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linearone said:
I keep telling people this. Unless you have a source for good used thats reliable... these tubes are worthless to lust after. For all its merits it is still an odd ball tube with limited availability.

This is why I try to steer folks towards tubes that are readily available from a multitude of sources with warranties that have a future.

I hope you can build it though. It would be a fun project.
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This was my line of thought. I was looking at some ebay history, and they appear to have gone up ~$50 or so over the last 6 months, very roughly speaking. Even if I could get my hands on 2 for $800-$1000, run them as speced out by Eimac, not +10%, or plus 20%, but at spec and 200pep drive, one tube and a spare should last a guy a very long time.
 
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359 said:
How much surface rust does it take to hinder heat dissipation?

yc156.jpg
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This tube just went for $338.

I'm figuring $300-$400 for a working pull, and $400-$500 for a tested and guaranteed pull. For how long, I don't know.
 
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linearone said:
I keep telling people this. Unless you have a source for good used thats reliable... these tubes are worthless to lust after. For all its merits it is still an odd ball tube with limited availability.

This is why I try to steer folks towards tubes that are readily available from a multitude of sources with warranties that have a future.

I hope you can build it though. It would be a fun project.
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Actually, the only real drawback that I can see so far is that Econco does not rebuilt this tube.

The YC-156 is out of production but can still be purchased new for $800 and change, and used for less than $400 (which will eventually dry up). The 3cpx5000a7 is still in production and be purchased new for $700 and change.

So compare those prices and gain to the popular 3cx3000a7 or equivalent and I still think the YC-156/3cpx5000a7 is a viable option.
 
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Nice tube doesnt require tons of drive or a socket.But requires 6 mins before hv is applied.I wouldnt mind having a couple any still left for sale guarenteed full output.
 
Shockwave said:
Start asking most 11 meter amp builders questions like how do you handle negative screen current, what impeadance transformation and Q is appropriate for the grid input circuit, how to regulate the screen and bias supplies, or how to safely neutralize a large tetrode and you get that "duhhhh" look! Sure the tetrode has significant advantages over the triode in terms of gain and reduced drive power. The number of large broadcast tetrodes properly working on this band can probably be counted on your fingers.

Simple protection of any grid can be done without significant added cost. All it requires is the use of inexpensive opto-couplers that interrupt your keying relay and are triggered off existing meter shunt resistors. Ameritron has grid protection with an add on board for $30 that could be adapted for screen grid use on a tetrode.

Those pesky screen bypass caps blowing up just when the amp starts making good output has plagued tetrode builders for years. This is a big tetrodes way of insisting you build it a shunt regulator for it's screen grid. It's all about secondary emissions and negative screen current that wants to drive the screen voltage up towards the anode voltage through this second current path within the tube. Strict control over the screen voltage is the way to get the tetrode linear to "take off" without a bang.

No matter how well you design a tetrode amp it almost always requires neutralization because of the high gain. This has to do with the inter-element capacitances within the tube that tends to couple the input stages to the output stages, causing the amplifier to oscillate. Neutralization cancels this problem by taking a small sample of the output, feeding it through a cap or coil to invert it's phase 180 degrees and applying this signal back to the input.
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Yes tetrodes are tricky,Im almost finished with a large grid driven tetrode which i built from scratch.As far as i know its the first one of its kind on this band.It has taken me over 2 years to complete i had brain surgery which slowed me down a bit.Im waiting for my custom front panel which is being cut by the same guys who make the rollers for the landing cable on the aircraft carriers.They have a cnc machine so the 7 holes for the 3.5 inch custom modutec meters will come out perfect.

Tetrodes are very fragile you must have protection.Screen regulation isnt as important on am as sideband.Yes there could be some negative screen current but its the imds which will cause you to stand out on the ham bands if the screen and bias supplies arent rock solid.I have a regulator which consists of 20 zener diodes and 20 bipolar transistors mounted on a heatsink which i may use.The screen transformer has 4 secondary taps so i can switch the screen voltage around via vacuum relays to adjust the gain of the tube.Of course i would have to readjust the bias voltage setting for the proper no signal plate current.

If you have the right bypass caps around the screen ring you wont have any problems.But if you have cheap mexico caps and the tank circuit is way out of tune then yes you will pop some caps.But as long as you have the proper protection the box will not key and it will be ok.But there is a way around this you could always ground the screen like rich measures explains on his website and use a center tap filament transformer to much to explain.I think his site is somis.org.

If the box is built right it will last a very long time.Theres nothing like not needing a driver.Lots of work but also alot of fun.

Proper neutralization of a tetrode isnt that hard to acomplish and can be done with the tube totally cold not a single voltage applied.Same with the setup of the input circuit.

For procedures please feel free to drop me a pm and i will do my best to help.
 
First you can buy ready made boards to make this easier.....The real thing is the cost factor. Old Surplus Russian tubes that function fantastically easy in super simple grounded grid format make it too affordable to play with anything else.

I am a first time builder and I am playing with triodes, tetrodes and pentodes but almost all of them are Russian because you can afford to play! Tubes Eimac makes are too darn expensive end of story.I can buy a 3500, 7000watt, 10,000watt tube for under $200off ebay.
 
ElectronTubesRule said:
First you can buy ready made boards to make this easier.....The real thing is the cost factor. Old Surplus Russian tubes that function fantastically easy in super simple grounded grid format make it too affordable to play with anything else.

I am a first time builder and I am playing with triodes, tetrodes and pentodes but almost all of them are Russian because you can afford to play! Tubes Eimac makes are too darn expensive end of story.I can buy a 3500, 7000watt, 10,000watt tube for under $200off ebay.
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Last time I looked the only really easy Russian tube to work with was the GS-35B.

Ceramic tetrodes usually will not work by tying the control and screen grids together so that is out.

The higher dissipation triodes seen for sale from Russia are medium to lo mu and will not behave well in grounded grid.
 
Best of luck with a YC-156. I have one that has to go with the amplifier project it was supposed to be installed into. It's been here for 6 years or more. The amp was made with a 4CX1000, but the mechanical rearranging to fit the larger tube and chimney has been done. It's a part-completed amplifier someone else had started. But just to make sure the whole thing goes away, the amp and tube together will go for $1200 cash.

And if someone asks "how much for just the tube" it will be $2400. Gotta provide incentive to get the whole thing out of my way. If they'll pay double to skip hauling away the hulk, I can afford to pay someone to make the rest of it go away.

73
 
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nomadradio said:
Best of luck with a YC-156. I have one that has to go with the amplifier project it was supposed to be installed into. It's been here for 6 years or more. The amp was made with a 4CX1000, but the mechanical rearranging to fit the larger tube and chimney has been done. It's a part-completed amplifier someone else had started. But just to make sure the whole thing goes away, the amp and tube together will go for $1200 cash.

And if someone asks "how much for just the tube" it will be $2400. Gotta provide incentive to get the whole thing out of my way. If they'll pay double to skip hauling away the hulk, I can afford to pay someone to make the rest of it go away.

73
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Thinking about this.
 

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