Eimac 254W

[W8ACR]

I recently fired up a new hombrew rig which has an Eimac 254W in the final. At 1400V and 150mA plate current, the plate was a moderately bright red. I am unfamiliar with this toob and didn't know if this was normal. I was wondering if anyone out there has experience with this toob. I haven't had this rig on the air yet, just making some initial observations and adjustments. Got some tweaking to do yet and gotta get the modulator up and running as well.

Thanks,  Ron W8ACR

[WQ9E]

Ron,

Is that a tantalum anode in the 254W?  If so, once you approach its 100 watt dissipation rating that bright red will change to orange.

According to the RCA air cooled transmitting tubes manual, tantalum plates will show some color even when operating under a fairly light load and will begin to glow orange red when running near rated power.

Rodger WQ9E

[KM1H]

That was their ruggedized WW2 response to the H&K 254. It later morphed into the 4E27 with little or no change.

Carl
KM1H

[N3DRB The Derb]

http://home.comcast.net/~n6jv/254w.html

254 is a triode. couldnt have become a 4e27.

throw about 2500 volts on that tube and watch it sing for it's supper.

[KM1H]

Sorry about that! Gee whats a few digits between friends anyway; 254 or 257

I can find only a few Eimac references to a 254 and it doesnt list operating data or why the W (ruggedized) designator. However the H&K 254 is well represented below and is in between a 100TH and 100TL for gain.

http://scottbecker.net/tube/sheets/114/h/HK254.pdf

And some nice Eimac photos

http://www.tubecollection.de/ura/eimac.htm

And one is currently on Fleabay with no bids

140371705752

Carl
KM1H

[KE6DF]

Here is the Penta Labs version:

[N2DTS]

Looks like an ugly 100TH to me.

I remember early in the learning curve, a friend telling me he could not get any power out of his 4-125 rig, something was wrong with it, when he went over not much power out, the plate started glowing red hot!

Well, tubes like 100TH's make the 4-125 look cold!

Its very cool to run tubes with almost white hot plates and watch them pulse under modulation!

813's are great, but dont look like much.
811's also work great, but better with no color, along with most other tubes.
4-xxx series tubes look good glowing, but only orange (wimpy).
But it would be very cool to have a homebrew rig using all 100TH/TL type tubes with the plates looking like they have to melt when you run the rig.
I have a push pull paralell 100TH mod deck, that thing scares me sometimes...
Why dont those plates vaporize?
They look like they are almost see through...crazy stuff, but very impressive.

Brett

[W2PFY]

I was wondering if anyone out there has experience with this toob

Would you please post some pictures of that amplifier? I have seen that tube in a 1941 had book for a HF amplifier.

About thirty years ago a guy gave me a couple that came out of a Link VHF transmitter that was used on the Tennessee Gas Pipe line. They looked like a rather modern tube for the era. I started collected them for a future projects I have various brands and some are NOS and others used. To date I have about 15 of them. They show up on ebay once in awhile. One is on there now but I think air might have gotten into that one. If you live near a pipe line, you could stop by and see the maintenance guys and ask them what old radios they may have in the back room. You may think there's nothing left. You'd would be wrong. People are pack rats by nature

Fleabay

I like that! May I use  your word??

[W2PFY]

H&K 254

Nice PDF on the H & K version. Nice data for construction of grid  tank circuits as well.

[w1vtp]

I was wondering if anyone out there has experience with this toob

Would you please post some pictures of that amplifier? <snip>...

Fleabay

I like that! May I use  your word??

YES! YES! PLEEEZE, PRETTY PLEEZE?

That sort of pic might even make a good Wondoz desktop background especially if it were taken with ambient light with the toobs glowing

Al

[N3DRB The Derb]

datasheet for the H&K version.

[W8ACR]

Thanks for the replies. Yes this tube has a tantalum anode, so maybe it's supposed to run red hot. As I recall, 304TH's run red hot plates, so maybe this is the same type of deal. I'll post some photos of the rig when I get it done, but don't expect it to look like that professional job at W5HRO - I'm not that good!

Ron W8ACR