WTB: 8950 Tubes
Boe737ing
Im needing (5) 8950 tubes....brand new....if you have any or no where I can get
them please e mail me with price or place and there price....would greatly
appreciate it....
73's
WWC 311
><HTML><PRE>Subject: WTB: 8950 Tube
THERE ARE 2 SOURCES THAT CURRENTLY HAVE
8950 TUBES NEW. BE PREPARED TO PAY 75.00 TO
90.00 PER TUBE . THEY ARE BECOMING A RARE
TUBE. 1. RF PARTS IN CALIFORNIA 2. ANTIQUE
RADIO SUPPLY. IF YOU HAVE PROBLEMS GETTING
THE ADDRESS OR PHONE NUMBER E-MAIL ME
AT WWC311.AOL.COM
drg...@ziplink.net
It aint even worth it unless you have a piece of good, mint radio gear
that takes these things...... if its just an amp, junk it and buy
something with 811s, 572b's, or 3-500z's.... these tubes are mass
produced, much more powerful, and CHEAP compared to an 8950. (well,
maybe not the 3-500, but its more powerful than than the friggan
8950..... )
I own a maco Amateur 200. If I can't retube it with something cheap
when the 8950s die, It goes in the trash! Although, I'll probably
die before it does, they're all in good shape, and I don't really push
the amp hard.....
-Mike
Toll Free
Eimac quit production of the 3-500Z. We are left with RF Parts brand.
--
1-800 Toll Free
One of da Big Johnson Boys in the 'Dome!
Every woman likes a man with a great big Johnson
dennis W. Ostrowski
Toll Free wrote:
>
> Eimac quit production of the 3-500Z. We are left with RF Parts brand.
>
TF,
I didn't know RF Parts was in the tube business!
I know that some folks 'private-label' other manufacturer's products.
I thought EIMAC simply spun-off it's varian division but but the same factory
was still making the same tubes. I'm not sure of that though...
Have a good day,
Dennis
#12
dennis W. Ostrowski
drg...@ziplink.net wrote:
> I own a maco Amateur 200. If I can't retube it with something cheap
> when the 8950s die, It goes in the trash! Although, I'll probably
> die before it does, they're all in good shape, and I don't really push
> the amp hard.....
>
> -Mike
--------------------------------------
Mike,
There are many, many tubes with the same base pin-outs as the 8950. The 6LF6
is one of them, but there are may more.
A trick I have successfully used is to purchase New Old Stock (NOS) of the
higher filament voltage TV sweep tubes, such as the 40KD6, then simply rewire
the sockets to put three tubes in series across the 120vac power coming into the
amp. This gives you an amp that uses the very cheap tubes that no one wants and
it also 'unloads' the power transformer in the unit because it no longer has the
filament 'load' on it.
The result is usually a little higher power output and low maintainance costs.
Dennis
#12
Toll Free
They did spin off the Varian Div., but when CPI bought them, they soon sold
off all glass tube manufacturing, including the licensing of them. A
company back east bought it (Thompson rings a bell, but I don't think that's
right), and they announced a couple months ago that they will not be brining
the lines back up with the 3-500, 3-1000, 4-400 and 4-1000. I believe all
the 4X tubes (old glass predecessors to the 4CX tubes) will not be brought
back, either.
kd5...@flash.net
does this produce clean linear amplification?
If so, that does sound interesting, I know several
people who run maco 750's........
Dale Powell
Why do people still worship those lousy sweep tube linears? For the price
of a handful of 8950's you could go to a ham swap and buy a real linear,
with tubes that are designed to last 20 years-
Boe737ing wrote in message
<199805191820...@ladder03.news.aol.com>...
kd5...@flash.net
On 21 May 1998 02:37:31 GMT, paink...@aol.com (PAINKI6669) wrote:
>if your going to use 3-500s best thing to do is use a 3-5oo zg the graphite
>added ones..thats what i heard anyway.Im not a fan of glass stuff.ill take
>ceramic anyday
a pair of 4cx250b's will do 1000 watts ssb all day for years with
proper air flow. WITH ONLY 3 WATTS DRIVE
a pair of 4cx400's will do 1600 with the same
hmmmm
and they are not THAT expensive
Five Watt Wizard
>Why do people still worship those lousy sweep tube linears? For the price
>of a handful of 8950's you could go to a ham swap and buy a real linear,
>with tubes that are designed to last 20 years-
>
>
Well , actually the 8950 tube is not a "sweep tube". If the
tubes were used within their specs. & the amp made well, 8950's would
last 20 years. There were even several small ham amps that used
8950's...
Five Watt Wizard
drg...@ziplink.net
>drg...@ziplink.net wrote:
>
>> I own a maco Amateur 200. If I can't retube it with something cheap
>> when the 8950s die, It goes in the trash! Although, I'll probably
>> die before it does, they're all in good shape, and I don't really push
>> the amp hard.....
>>
>> -Mike
>--------------------------------------
>
> Mike,
>
> There are many, many tubes with the same base pin-outs as the 8950. The 6LF6
>is one of them, but there are may more.
>
> A trick I have successfully used is to purchase New Old Stock (NOS) of the
>higher filament voltage TV sweep tubes, such as the 40KD6, then simply rewire
>the sockets to put three tubes in series across the 120vac power coming into the
>amp. This gives you an amp that uses the very cheap tubes that no one wants and
>it also 'unloads' the power transformer in the unit because it no longer has the
>filament 'load' on it.
>
> The result is usually a little higher power output and low maintainance costs.
>
>Dennis
>
>#12
Wait, use three instead of four tubes? (My amp is set up for radio
driving all four, not 1 8950 driving three..... )
You make this sound easy.... theres gotta be a DOWN side to this...
:) Is the output going to get cleaner or dirtier? how about those
nifty "tune" and "load" controls on the amp... I suppose those will
change a ton too... As it is right now I have to turn the load
control all the way to the left till it hits the peg, to get most of
the power out.
-Mike
drg...@ziplink.net
I thought the 4CX250 was a" VHF" transmitting tube. maybe the "b"
version is different?
OTOH, I probably dont have a clue about these and am just babbling!
-Mike
drg...@ziplink.net
>Why do people still worship those lousy sweep tube linears? For the price
>of a handful of 8950's you could go to a ham swap and buy a real linear,
>with tubes that are designed to last 20 years-
Hey!! the 8950 is NOT a Sweep tube!!!
(At least not that I know of, AFAIK, its designed for transmitting,
and I'd doubt youd find one in an old TV set!)
-Mike
drg...@ziplink.net
>Eimac quit production of the 3-500Z. We are left with RF Parts brand.
Irregardless, Toll, that tube is here to stay. the 500-ZG, and other
variants. There are just too many damn amps that take this tube, so
the demand is enough that someone will keep making them.
-Mike
Toll Free
Your right, but the problem lays in that people are buying up the "Better"
graphite tube. In some of the old designs, this has been causing a problem
with parasitic oscillations, as the Penta and Pride and RF Parts re-brand
all have higher Mu (Gain) than the old Eimac tubes. If you keep your amp in
the 10 meter position then you have nothing to worry about (usually), as the
other contacts are (usually) closed. BUT, if you go to 20 or 40 meters,
then the open contacts have the opportunity to burn up, as you get a large
BANG in the amp. That is parasitic oscillations, and they can kill a tube.
One preventative measure is to insert a resistor of a few ohms in line with
the grid. That can protect the grid structure in the case of a parasitic,
as the resistor will open up before the tube is KILLED!
dennis W. Ostrowski
Toll Free wrote:
> They did spin off the Varian Div., but when CPI bought them, they soon sold
> off all glass tube manufacturing, including the licensing of them. A
> company back east bought it (Thompson rings a bell, but I don't think that's
> right), and they announced a couple months ago that they will not be brining
> the lines back up with the 3-500, 3-1000, 4-400 and 4-1000. I believe all
> the 4X tubes (old glass predecessors to the 4CX tubes) will not be brought
> back, either.
--------------------------------------
WOW! That's a lot of shuffling!
I guess all the glass bottles will be 'relabled' overseas production then!
It just made all of my NOS (new old stock) Eimac bottles become that much more
valuable!
Have a good day!
Dennis
#12
dennis W. Ostrowski
kd5...@flash.net wrote:
> On 21 May 1998 02:37:31 GMT, paink...@aol.com (PAINKI6669) wrote:
>
> >if your going to use 3-500s best thing to do is use a 3-5oo zg the graphite
> >added ones..thats what i heard anyway.Im not a fan of glass stuff.ill take
> >ceramic anyday
>
> a pair of 4cx250b's will do 1000 watts ssb all day for years with
> proper air flow. WITH ONLY 3 WATTS DRIVE
> a pair of 4cx400's will do 1600 with the same
> hmmmm
> and they are not THAT expensive
And I have an amp on my bench running 'baised' 3-500Z's ( not even the
Graphite plated ones) that will do over 3000 watts on SSB. ( since it is
grounded grid and not grid-driven; it does take more drive to do the job; and
that's were the conservatively run grid-driven 4CX250 is used!
By the way, one of my 'favorite' tubes is the 4CX300Y, because of it's
breachblock base and for it's 400 watts plate dissipation in a package as small
as a 4CX250....
Dennis
#12
dennis W. Ostrowski
kd5...@flash.net wrote:
does this produce clean linear amplification?
If so, that does sound interesting,
------------------------------------------------
They are as 'linear' as any other sweep tube amp ever was!
They won't replace the M-2057's for power dissipation, and you may have to 'retune'
the tank circuits, but the XXKD6 , XXLR6 , XXLB6 , and XXF6 tubes will all do a
respectable job of replacing the 8950 tubes in any of those old sweep tube amps....
XX being the new and higher filament voltage....
I have successfully converted many amps over without any reduction in power out or
functionality.
Dennis
#12
dennis W. Ostrowski
Toll Free wrote:
> Your right, but the problem lays in that people are buying up the "Better"
> graphite tube. In some of the old designs, this has been causing a problem
> with parasitic oscillations, as the Penta and Pride and RF Parts re-brand
> all have higher Mu (Gain) than the old Eimac tubes. If you keep your amp in
> the 10 meter position then you have nothing to worry about (usually), as the
> other contacts are (usually) closed. BUT, if you go to 20 or 40 meters,
> then the open contacts have the opportunity to burn up, as you get a large
> BANG in the amp. That is parasitic oscillations, and they can kill a tube.
>
> One preventative measure is to insert a resistor of a few ohms in line with
> the grid. That can protect the grid structure in the case of a parasitic,
> as the resistor will open up before the tube is KILLED!
-------------------------------------
TF,
The REALLY old Eimacs were also higher MU tubes, and so are the Amperex. It
was only relatively recently, (the last 15 years or so) that the Eimac 3-500Z's
had a lower MU ( reduced to 40 from 100).
An old ham friend from the West coast came up with a pretty nice 'fix' for the
parasitic problems in the 3-500Z and also the 3CX1500/8877. He uses Nichrome
wire to wind the parasitic chokes...... And it seems to work.
Dennis
#12
dennis W. Ostrowski
drg...@ziplink.net wrote:
> >#12
>
> Wait, use three instead of four tubes? (My amp is set up for radio
> driving all four, not 1 8950 driving three..... )
If you need 4, adjust the filament voltage... 120/4 = 30 volt filament 120/3 = 40
volt filament , etc...
You may not find a 30 volt tube available, but could use a 36 instead and not
notice the undervolted filament because it is not that critical when you get over 24
volts.... Or you could use 24 volt tubes and a series current limiting resistor to
drop the additional voltage .
> You make this sound easy.... theres gotta be a DOWN side to this...
You have to be familiar with the amp and know what you are doing; because some amps
(actually most of them) tap off the filament supply for keying circuit voltages and
grid bias voltages. You have to move those circuits because the 120volts would
certainly destroy them. You also need more RF bypass caps across the filament pins
to ground and some rf decoupling from the power line feeding the filaments so that
you do not send the RF into the power system of your house....
Any reasonably compitent tech should be able to do the job...
> :) Is the output going to get cleaner or dirtier?
It should stay about the same.
> how about those
> nifty "tune" and "load" controls on the amp... I suppose those will
> change a ton too...
That depends on which tubes you use.
If you replace 6lq6's with 24 lq6's, the controls should remain exactly the same..
If you replace a 8950 with a 36LB6, the controls may tune differently and you may
even have to change the inductance value in the tank circuit to compensate for tube
capacitance variations along with transconductance variations..
> As it is right now I have to turn the load
> control all the way to the left till it hits the peg, to get most of
> the power out.
Is that with the loading capacitor plates fully meshed or fully unmeshed?
and where is the tune capacitor tuning? Just slightly meshed, half way meshed, or
where?
Dennis
#12
>
Toll Free
Sounds like your talking about Rich Measures??????
dennis W. Ostrowski
Toll Free wrote:
> Sounds like your talking about Rich Measures??????
>
Nope!
His name is Joe Funderburg, and I don't know his call letters but he
was in the 805 area code...
I believe he and Bill Orr co-wrote a few articles in QST dealing with
the problem and the solution as applied to 8877 tubes.
Dennis
#12
Bill Nelson
drg...@ziplink.net wrote:
:
: I thought the 4CX250 was a" VHF" transmitting tube. maybe the "b"
: version is different?
If it will work at VHF, then it most likely will work fine at HF.
The limitation usually goes the other direction. The UPPER frequency
limit comes when there is too much interelectrode capacitance.
An example of using tube at much lower than design frequencies is the
"golden ear' crowd using sweep tubes (and even higher power ceramics)
in their audio amps.
--
Bill Nelson (bi...@peak.org)
Toll Free
No, the 4CX250 tube isn't that expensive, but the sockets are nearly the
same price as the tube! I have a dual 250B amp that I am building now, and
I expect 1400 out of it (My old Pride DX300 would do 300 Bird, 700 PEP).
That is with 2200 on the plate (A little high), 350 screen, 6.0 filament and
near -80 grid. I am just trying to round up all the transformers to do the
job (Peter Dahl has a X-Former, but it is WAY to high, in my book).
I got my sockets from RF Parts, and they where used, but $45.00 for the
pair.
Toll Free
Toll Free
With the tube run properly, you can get 20 plus years out of it. My SB220
has a date on the receipt of 1971 and it has the original tubes in it. It
will run 1700 watts output, and that is on 110 volts! You are right, the
tubes will continue to be made, BUT not by Eimac.
RH3333
RIchard Hale NOTE: I have 8950 for $60
THE TUBE MAN 8908 for $80
850 386-2729 3-500Z Graphite-$105
850 386-2560 FAX 6JE6/6LQ6-$18 Used for 10+
RH3...@aol.com 4CX250B-$80
I currently have over 200,000 new tubes in stock including Transmitting,
Receiving, Audio, TV, Antique, Ceramic.
I do not have a Web Site nor a price list. Suggest that you Email/FAX a list
of the tubes that you are looking for as well as a quanity of each needed. I
will check my inventory and advise you of current availibility and cost.
Also have a good supply of tube tester, tube caddies, and used tube equipment.
Thank you for your interest.
dennis W. Ostrowski
Toll Free wrote:
> No, the 4CX250 tube isn't that expensive, but the sockets are nearly the
> same price as the tube! I have a dual 250B amp that I am building now, and
> I expect 1400 out of it (My old Pride DX300 would do 300 Bird, 700 PEP).
That's pushing those 250B's WAY too hard! Even too much for 250R's!
Take a look at the 4CX1500B. It will work in the same circuit with the same
bias voltages
and easily give you that power output, DEAD KEY!
> That is with 2200 on the plate (A little high), 350 screen, 6.0 filament and
> near -80 grid. I am just trying to round up all the transformers to do the
> job (Peter Dahl has a X-Former, but it is WAY to high, in my book).
>
> I got my sockets from RF Parts, and they where used, but $45.00 for the
> pair.
Next time try Fair Radio sales in Lima Ohio. If the used sockets you got at RF
partsare the ones I think they are, they bought them from Fair Radio.
Dennis
#12
drg...@ziplink.net
>> As it is right now I have to turn the load
>> control all the way to the left till it hits the peg, to get most of
>> the power out.
>
> Is that with the loading capacitor plates fully meshed or fully unmeshed?
I forget..... I think it probably is fully unmeshed.
> and where is the tune capacitor tuning? Just slightly meshed, half way meshed, or
>where?
Its in between, id say about halfway, changes depending upon the
channel im using, etc.
dennis W. Ostrowski
drg...@ziplink.net wrote:
> >> As it is right now I have to turn the load
> >> control all the way to the left till it hits the peg, to get most of
> >> the power out.
> >
> > Is that with the loading capacitor plates fully meshed or fully unmeshed?
>
> I forget..... I think it probably is fully unmeshed.
Then you need less load capacitance or a smaller plate tuning inductor.
First check and see if there is a 'fixed' value of capacitance in parallel with your
output load capacitor. They sometimes add 'padder' capacitors to resonate a tank
circuit. If there is one there, remove it and see what happens.
> > and where is the tune capacitor tuning? Just slightly meshed, half way meshed, or
> >where?
>
> Its in between, id say about halfway, changes depending upon the
> channel im using, etc.
That's an indication that the tune capacitor and loading coil are more or less the
correct values.
But I prefer a little more inductance in the tank circuit so I would probably squeeze
the coils of the tank circuit inductor together a little more so that I could use less
plate tuning capacitance....
And I would once again look for a 'padder' capacitor across the loading capacitor.
One last possibility is that the grounding connections on the loading capacitor have
become resistive. I often add a braided strap of solder wick to connect the ground of
the capacitors (tune and load) directly to the chassis. I do this to improve the
circuit 'Q'.
Hope this helps,
Dennis
#12