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3-500z/4-400a socket choices




 
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Author Topic: 3-500z/4-400a socket choices  (Read 426 times)
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wa1knx
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« on: July 17, 2017, 08:06:40 PM »

    I've got some 3-500z and 4-400a tubes and thinking about sockets, which is best.  the sk-410 eimac style,
or the johnson 275 mounted a bit below chassis.  Or a metal style, looks intriguing.  included some pics wonder
what others think..



* sk410.jpg (110.16 KB, 750x750 - viewed 26 times.)

* 122-275-204_1.jpg (51.11 KB, 650x556 - viewed 19 times.)

* s-l1600.jpg (60.12 KB, 800x630 - viewed 24 times.)
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KF7WWW
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« Reply #1 on: July 17, 2017, 08:24:53 PM »

I like the sk410's.. I also use oversized blowers and chimneys on tube like the 500z.
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W1ITT
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« Reply #2 on: July 18, 2017, 11:02:42 AM »

At HF, and with continuous modes like AM, cooling is the overriding factor for me.  I like the SK-410 series.  I used that type on a few 4-1000A rigs over the years.
Dayton sells a few blowers that roll at 1800 rpm rather than the more common 3600 rpm units.  The difference in noise is significant, and the air noise produced seems to have fewer high frequency components,  is gentler on the ears and seems to produce a shack ambience that bespeaks confident power.   
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w8khk
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« Reply #3 on: July 18, 2017, 11:28:24 AM »

I prefer the SK-410 style, because it allows better air flow with less resistance.  I used this style for my 4-1000A rig.  As David mentioned, a slow blower with lots of air flow is preferred, and this socket may help you realize that goal more easily.  Any restriction causes more turbulence, thus more noise.

Back in 1969, I built a legal-limit amplifier with a pair of 4-400As using the Johnson 275 sockets.  I did not sub-mount them, just bolted them to the bottom of the chassis top plate.  I put a 5 x 8 x 2 inch chassis up-side-down under the socket area, and one four-inch muffin fan blowing air through the sockets to the tube seals, and over the tube with a chimney.  That amplifier was used heavily for CW, SSB, and RTTY until around 2010, and still works fine with original tubes.

I was advised by Bill Orr that it is unwise to drill holes around the outside of the tube socket, because it is best to have all the air flow cooling the seals around the pins.  With a chimney, there will be sufficient air flow around the plate seal using this method. 
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Patrick J. / KD5OEI
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« Reply #4 on: July 18, 2017, 11:30:31 PM »

I prefer the metal type. The pin mounts are ceramic. No plastic to craze or break.
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wa1knx
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« Reply #5 on: July 19, 2017, 01:30:45 AM »

        The sk-410 is what I have been thinking, however Pat those metal sockets caught my attention
to.  For a couple of reasons, one being the extra spring metal clamping the pins.  I had a couple of 3-500z
failures over the years. One, a TL-922A amp had been in storage for some time.  Upon firing it up
bam.  I lost a 3-500z.  Thats been explained in other notes around the gassing up from shelf life
problems. Its getter is in the anode.

         The other was a Sigma XR-3000D amp.  the solder melted out of the pins.  I resoldered the
tube pins and found the cooling fan had a resistor in series with the fan.  A feature was its quiet
running time in its manual ( ? ).  I jumped the fan resistor and it ran well after. both amps are gone.

         I have sk-406 chimneys, did you use them with the metal sockets Pat? I am not sure if the
pins are located right for those chimneys.   I looked up plate modulating 3-500z's. turns out
they work well if you drive them hard.  Theres a good discussion on redwaveradio.com

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« Reply #6 on: July 20, 2017, 12:26:55 AM »

I used Coleman lamp glass for chimneys, not having the correct items. It is not perfect but the blower is over-large and enough air follows the tube envelope to the anode coolers. I don't know if the Eimac-spec chimneys fit. I guess it would be a matter of measurement. The way the metal ones are made, the air coming up has to hit those metal contacts from all around. I'm not an expert on cooling but I like the results so far with the sockets.
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