4-400a vs NL10277-1

[k7iou]

I have a NOS NL10277-1 Tube and I wanted to know the interchangeability with the 4-400a?
I am considering using it in my Johnson 500.
Here is a link to the PDF
http://www.rell.com/filebase/en/src/Datasheets/NL10277%20Series.pdf
Thanks

[WQ9E]

That should work fine in your Viking 500, the NL is clearly a relative of the 4-400 family.  The -1 variant appears not to have the metal base surround but the cooling system in the 500 is definitely low tech so that shouldn't matter.

A 4-250 will also work fine in your 500, mine came with an Amperex final that appears to be their version of the 4-250 and I have been using it for 8 years.  If you use it on SSB at rated input the 4-400A or similar is desirable but a 4-250A is easily within its ratings for AM/CW usage.  For longest tube life a bit of air across the plate seal is desirable.  That omission along with lack of 160 meter coverage (but a VFO scale that shows 160) are the only things I dislike I about my 500.

Make sure to address the delay relay problem in the 500 if you aren't using a vacuum T/R relay, otherwise as the delay relay slowly loses its delay characteristic the properly adjusted protective arc gap will file upon PTT release and if the gap isn't set properly the arc will occur somewhere else and may prove destructive.  I added a small capacitor and isolating diode across the relay coil to provide a short antenna relay delay upon PTT release.  Outside of correcting the delay relay problem the only other failure in my 500 was an open mic gain control that I repaired over Thanksgiving.

[k7iou]

Thanks Rodger, mine came with the 4-400a and the delay mod along with a small audio mod were done by the previous owner. The 4-400a seems a little soft but it works.
Thanks for the info.
Very nice desk!
73 de k7iou

[W2PFY]

[Make sure to address the delay relay problem in the 500 if you aren't using a vacuum T/R relay, otherwise as the delay relay slowly loses its delay characteristic the properly adjusted protective arc gap will file upon PTT release /quote]

So I gather that a vacuum relay is the answer? I hope to put the Desk KW on next summer. Any suggestions are appreciated and I note that the Russian VR's can be had for little money...

Just a side note. Windows 8.1 for what ever reason will not handle the QUOTES very well? It always groups my comments in the same box as the quote?

[Opcom]

http://www.rell.com/filebase/en/src/Datasheets/NL10277%20Series.pdf

wow. Holy laser beams Batman!

[Pete, WA2CWA]

[Make sure to address the delay relay problem in the 500 if you aren't using a vacuum T/R relay, otherwise as the delay relay slowly loses its delay characteristic the properly adjusted protective arc gap will file upon PTT release/quote]
So I gather that a vacuum relay is the answer? I hope to put the Desk KW on next summer. Any suggestions are appreciated and I note that the Russian VR's can be had for little money...

Just a side note. Windows 8.1 for what ever reason will not handle the QUOTES very well? It always groups my comments in the same box as the quote?

Has nothing to do with Windows 8.1.

Left bracket in front of Make is in the wrong place. Shouldn't be there
At the end of the quote (the word release), there should be the left bracket which is missing .

A quote should always have a left bracketQUOTEright bracket (no spaces) at its beginning and a left bracket/QUOTEright bracket (no spaces) at the end.
A extra left or right bracket or a left or right bracket in the wrong place, will screw up a quote. If you put the quote brackets in their correct location, your post will look like this:

Make sure to address the delay relay problem in the 500 if you aren't using a vacuum T/R relay, otherwise as the delay relay slowly loses its delay characteristic the properly adjusted protective arc gap will file upon PTT release

So I gather that a vacuum relay is the answer? I hope to put the Desk KW on next summer. Any suggestions are appreciated and I note that the Russian VR's can be had for little money...

Just a side note. Windows 8.1 for what ever reason will not handle the QUOTES very well? It always groups my comments in the same box as the quote?

[W2VW]

Terry, r u going to call it the empire buster?

[W2PFY]

Pete, I just hit the INSERT QUOTE BUTTON or hit the button to the top right of the post if the topic or comments are not to large. In the first instance its copy and paste. I never had this problem until I got this new computer. So what ever the problem is, it started when I purchased this machine and it happens no matter what browser I use, be it a 32 bit or 64...Firefox, IE and the list goes on..So I will try it manually and see what happens? Now back to the regularly scheduled program

[W2PFY]

Terry, r u going to call it the empire buster?

I'm not sure. Come to think  of it, I haven't put names in any of my equipment. I know some people do that with their vehicles..

[W2PFY]

Terry, r u going to call it the empire buster?

this is just  a test...Looks like the copy and paste is working now...

[Pete, WA2CWA]

Ah! The miracles of proper placement.

Also make sure when you quote something and then go to add your message, you're not typing within the quoted message. How do you know: After you quote a message, and then add your response after it, look a line or two above where you start. You should see left bracket /Quote right bracket. If you don't see that, you're probably typing within the quote.

[WQ9E]

Terry,

I use a vacuum relay with my Desk KW but a regular relay with heavy contacts can be used.  I don't care for Dowkey relays because most of them are getting old with unknown hours on them and a failure can create damage.  The key thing for the Desk KW is to add some delay upon release for the T/R relay and unlike the Viking 500 the Desk KW wasn't meant to provide that delay control.

Johnson specifies adding a rectifier, capacitor, and suitable dropping resistor to power a standard Dow Key relay that has a 120V AC coil.  The capacitor must be sized to provide a slight delay upon PTT release while the resistor is chosen to provide reliable relay operation without overheating the AC coil now being powered by DC.

For mine I built an external relay box using a RJ1 series vacuum relay for antenna switching along with a standard cube relay to handle muting.  The relay is powered by a small transformer operated supply I built into the switch box and it is powered by the switched 120VAC provided by the Desk when the PTT is pressed.  I chose a filter capacitor/bleeder resistor combo to provide the amount of delay I needed.

Perhaps the biggest caution with the Desk KW, other than safety around HV, is the rails that the mainframe rolls upon inside the pedestal can spread outwards and if this happens everything drops to the bottom of the pedestal and then the pedestal must be cut open to retrieve the works.  The most typical approach is to wedge wood pieces between it and the side of the pedestal so that they cannot spread outward.  I replaced this part in mine with angle steel and roller bearings during rebuild.

[W2PFY]

Thanks Roger. I will follow you lead and replace the rail. Heading out now to the camp Maybe I will catch you and others around 7.290 Saturday & Sunday morning from about 11:30 to 12:30 eastern........

[k7iou]

I have a NOS 110v Dow Key still in the original package.   But I decided to build a 24vdc T/R relay. I used a 24v 10 amp relay and I purchased a 24v wall wart from electronic surplus for $6.95. I plugged it into the 110v plug for the Dow Key relay. I also used some double shielded coax which is same size as RG-58 but is rated for hi power HF for wiring the relay in a aluminum box. I had a spool of it laying around. Grounding the ends of the shield at the chassis mount SO-239. Works like a champ.