8950 Substitutes - I'm Confused!
DavidC
8950 tube. I found a discussion on DejaNews about this and
there was a suggestion that 6KG6A's are excellent.
I looked closely at the facts and there seem to be several
significant differences between the 8950 and all of the other
suggested substitutes. I don't understand how a 6KD6 or
6KG6 could be "forced into" a 8950 tube socket.
The 6KG6 is a Novar and I suppose the 6KD6 could fit in the
6KG6 socket but I don't think the 8950 is even close.
I think maybe folks meant that after the amp was modified from an
8950 to a 6KG6 one could substitute a 6KD6 for the 6KG6.
Can someone clarify please?
- Thanks again & Happy Thanksgiving to all! DavidC K1YP
**************************************************
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DavidC
;-)
Now, can anyone tell me from direct personal experience what tubes they
have directly substituted without mods for the 8950?
Results?
What tubes have you directly substituted for the 8950 with mods?
What mods did you have to do?
Results?
I'm looking at modifying a Palomar 12v Amp designed for one 8950 driving
three and wish to make the mod that generates the maximum output that is
distortion and garbage-free using the existing power supply (changing caps
or
other small components OK, changing transformers is not).
Thanks for all who have already offered helpful info! 73, DavidC K1YP
> There are many possible substitutes but I know of only 1 tube that will
> substitute without heater voltage modification: M2057 (not cheap) Heater
> voltage on the 8950 and the M2057 is 12.6 volts and is on pins 1 & 12 of
> the 12GW socket.
> Other tubes that use the same (12GW) socket but have different heater
> voltage are:
> 6KD6,6LF6, 6MH6, 20LF6, 30KD6, 36KD6, 40KD6 (there may be
> more that I am not aware of)
> Heater voltage is on pins 1 & 12 on all of these tubes.
> The 6LF6 may be a good substitute for you if can reduce the heater voltage
> to 6.3 volts. Bry
>
>
> Sounds like you are on a 'merry chase' on the 8950 sub quest.
> Here is the little bit I know. "Sweep" tubes derive the name from TV
> application only. It is actually a "horizontal output tube". Tube
> drives a sweep/HV transformer which drives the deflection coils on the
> neck of the CRT which deflects the beam horizontally. Vertical tubes do
> the same thing except for the HV work. Why one is called a 'sweep' tube
> and the other a 'vertical' tube I don't know. As a result of this, just
> about any 'sweep' tube will work, electrically, for just about any other
> sweep tube. Base and internal connections are different. Plate
> dissipation will be about the same for all - 30 to 35 watts. Capacitance
> will be slightly different but can be compensated for. Transconductance
> will be comparable. Dynamic plate resistance will be comparable. The
> reason one might work better in a given application is that the
> characteristics are matched better. The 12 pin 8950 has some internal
> connections to pins which are open on other tubes. That is not a problem
> - simply add an external connection to the socket pins. These tubes will
> all plug into the 8950 socket and, with careful attention to
> neutralization etc., will work just as well: 6LB6, 6JS6, 6KD6, 6LF6,
> 6LX6, and 6LR6. I say this with 'tongue in cheek' as I do not have
> specification data on many of them. But they are all sweep tubes, all
> have about the same characteristics, and all have the same 12 pin base.
> Of the ones where I do have data, the 6JS6A and 6LB6 draw 2.25 amps
> filament current. 6KD6 draws 2.85 amps. Well, here are the specs:
> Ih Cgp Cgk Cpk Zp Gm Ip Ep Pd
> 6JS6A 2.25 .7 24 10 5.6K 11.3K 570 990 30
> 6KD6 2.85 .8 40 16 6K 14K 750 990 33
> 6LB6 2.25 .4 33 18 6.6K 13.4K 560 990 30
>
> I can not speak accurately about tubes I've never used. But I can say
> with confidence that any of those tubes will work, and, with attention to
> detail, work as well as any other tube. Without changing sockets, but
> subtle changes in socket wiring and coupling, decoupling, bypass, and
> feedback capacitors as well as resistors which set biases.
>
> I know! I'm really not much help. Changing sockets to an octal socket
> would open up a great many other sweep tube possibilities and octal
> sockets are much easier to come by. Jim
W5IDX
Most Others Are Not Even 8 Volts
The 8950 Was A Mill Spec Sweep Tube Used In Several Amps Palomar, D&A Etc.
And The Siltronix Radio's In The Finals And A Few Others.
73's W5IDX
Good Luck.
DavidC wrote in message ...
>I recently asked about substitutes for the incredibly costly
>8950 tube. I found a discussion on DejaNews about this and
>there was a suggestion that 6KG6A's are excellent.
>
>I looked closely at the facts and there seem to be several
>significant differences between the 8950 and all of the other
>suggested substitutes. I don't understand how a 6KD6 or
>6KG6 could be "forced into" a 8950 tube socket.
>
>The 6KG6 is a Novar and I suppose the 6KD6 could fit in the
>6KG6 socket but I don't think the 8950 is even close.
>
>I think maybe folks meant that after the amp was modified from an
>8950 to a 6KG6 one could substitute a 6KD6 for the 6KG6.
>
>Can someone clarify please?
>
>- Thanks again & Happy Thanksgiving to all! DavidC K1YP
>
>**************************************************
>
>
>
>
Donnie
>I recently asked about substitutes for the incredibly costly
>8950 tube. I found a discussion on DejaNews about this and
>there was a suggestion that 6KG6A's are excellent.
>
>I looked closely at the facts and there seem to be several
>significant differences between the 8950 and all of the other
>suggested substitutes. I don't understand how a 6KD6 or
>6KG6 could be "forced into" a 8950 tube socket.
>
>The 6KG6 is a Novar and I suppose the 6KD6 could fit in the
>6KG6 socket but I don't think the 8950 is even close.
>
>I think maybe folks meant that after the amp was modified from an
>8950 to a 6KG6 one could substitute a 6KD6 for the 6KG6.
>
>Can someone clarify please?
>
>- Thanks again & Happy Thanksgiving to all! DavidC K1YP
>
>**************************************************
>
> What about a M2057 I think that will swap but as hard to find as 8950's 73 n4jzh Donnie
Bill Eitner
--
W5IDX wrote:
>
> There Are No Substitute's For The 8950 Mill Spec 8 Volt Tube....
> Most Others Are Not Even 8 Volts
> The 8950 Was A Mill Spec Sweep Tube Used In Several Amps Palomar, D&A Etc.
> And The Siltronix Radio's In The Finals And A Few Others.
> 73's W5IDX
> Good Luck.
--
-------------------------------------------------------------------
-=[Bill Eitner]=-
Link to A.M. Tutorial, rec.radio.cb FAQ
and The Dark Side:
http://kd6tas.conk.com
-------------------------------------------------------------------
Bill Eitner
>
> Wow! I think I am getting less confused ... a small Thanksgiving miracle!
> ;-)
>
> Now, can anyone tell me from direct personal experience what tubes they
> have directly substituted without mods for the 8950?
M2057.
> Results?
Works fine.
> What tubes have you directly substituted for the 8950 with mods?
6LF6, 6MH6, 6LX6, 6KD6, 6JS6.
> What mods did you have to do?
Filament rewiring and sometimes additional tank
capacitance. If you're using the tall versions
in an amp where the tubes are vertical, you have
to lower the board or chassis where the tube
sockets are and lengthen the plate leads. Some
of the amps where the tubes are horizontal
require mods to fit the longer tubes, and some
won't work with the longer tubes at all. The
long tubes are 5 inches long, and you need an
eighth of an inch of clearance above the plate
cap. The 6KG6/EL509 that's reasonably priced
is one of the tall types.
> Results?
They work fine.
> I'm looking at modifying a Palomar 12v Amp designed for one 8950 driving
> three and wish to make the mod that generates the maximum output that is
> distortion and garbage-free using the existing power supply (changing caps
> or
> other small components OK, changing transformers is not).
None of the sweep tube amps are especially clean, so don't
expect perfection when it comes to distortion. The crap
content in sweep tube amps is usually 5 to 10 dB higher
than in an equivalent ham amp that uses transmitting tubes.
The 6KG6/EL509 is the most powerful and is available for
a reasonable price, but it also requires the most effort
to make it work. The sockets have to be changed. They
use European 9-pin sockets--not Novar sockets. You can
force them into Novar sockets, but the sockets will never
hold the thinner-pinned Novar tubes afterward. The 6KG6
is a tall tube; you have to make sure you can fit them
in without shorting the plate cap to the chassis.
Personally, I wouldn't spend any money or time on a 12 volt
tube amp. They're big, noisy, wasteful, unreliable, costly
to repair, outdated piles in my opinion. I've had two 1-
driving-3 sweep tube mobiles: a Palomar 310M, and a PAL
350MDX; I converted them both to base amps by gutting out
the unreliable DC to DC power supplies and using 117CX
Swan power supplies that are separate from the amp itself.
The power supply connects to the amp through a jones plug
(similar to the Palomar 300A design). With the stock
power supply gone there's plenty of room for a fan to
help keep the tubes from overheating.
If you're curious and just can't resist making that amp
work, buy the cheapest tubes you can get ahold of, play
with the amp until you've learned all you can, and then
sell it for as much as you can. If the switching tran-
sistors in the power supply are still good, and you didn't
have to pay too much for the tubes, you may just be able
to come close to breaking even when you sell it.
If you need them, I have 6JS6As that will work in that
amp (once you rewire the filaments) for $20 each. They
are NOS, matched for gain (transconductance) RCAs in
their original 1966 vintage boxes. The "A" version of
the 6JS6 will produce as much power as an 8950, but has
a lower plate dissipation spec. What that means is you
have to be more careful when tuning the amp or the tubes
will overheat. When tuning the amp for the first time
you should have the cover off so you can make sure the
peak power output happens before the tuning caps reach
either minimum or maximum capacitance. In other words,
you want to make sure you can see both sides of the
peak before the plates on the air-variable caps (there
is one in the driver stage and two in the output stage)
are either fully meshed (maximum capacitance) or fully
unmeshed (minimum capacitance). If you don't do that
there very often is a false peak at either the minimum
or maximum capacitace position that makes you think
the amp is properly tuned, when in reality the output
isn't at maximum and the tubes are overheating because
they have to dissipate too much power.
Here's an applicable case history: I put a set of my
6JS6As in a Palomar Skipper 300. The Skipper 300 is a
1-driving-3 amp that is similar to the Palomar 310M
mobile amp. When tuning it for the first time I saw
both sides of the peak when tuning the driver cap, but
both output stage caps ended up at their minimum capa-
citance positions at what seemed to be maximum peak
(modulated) output. The maximum peak output was about
550 watts (measured on a powered, peak-reading meter
feeding a dummy load). I noticed that it only took
about 10 seconds of key-down time before the tube plates
began to glow. I knew the tubes wouldn't last long
running like that. I experimented with different
techniques to make the the output tank circuit (the
two air-variable caps and the coil in between them)
resonate with the caps near their half-meshed areas.
I didn't want to cut plates off of the caps, so I
tried other things. In the end, adding 30 pF to the
antenna load cap brought both caps back to near their
half-meshed areas. In other words, I could see both
sides of the peaks of both caps. The peak output
went up to 620 watts and it takes 2 to 3 times more
transmit time to make the tube plates glow. The amp
went back into service and the customer is happy with
it. The customer runs it on low (420 peak watts) to
keep the tubes cool and his neighbors happy.
> Thanks for all who have already offered helpful info!
You're welcome. I hope this helps.
> 73, DavidC K1YP
Toll Free
That guy was full of shit all the way around!
--Me
Bill Eitner <kd6...@netzero.net> wrote in message
news:383DF199...@netzero.net...
> The 8950 is a 12 volt filament tube.
> --
> W5IDX wrote:
> >
> > There Are No Substitute's For The 8950 Mill Spec 8 Volt Tube....
> > Most Others Are Not Even 8 Volts
> > The 8950 Was A Mill Spec Sweep Tube Used In Several Amps Palomar, D&A
Etc.
> > And The Siltronix Radio's In The Finals And A Few Others.
> > 73's W5IDX
> > Good Luck.
>
Donnie
>And the M2057 was the "Mil-Spec" version.
>
>
>That guy was full of shit all the way around!
>
>
>
>Wha!! You talkin to me?
Toll Free
Toll Free
''Donnie'' <n4...@amsat.org> wrote in message
news:383edda5....@news.mindspring.com...
Donnie
Toll,
I was the fellow that threw the M2057 into the equation.
8950's were a good tube BUT the M2057 was better.
Wished I had a truckload.
It would be me making the clay pots and hitting on the chick
in the commercial instead of Donald Trump. 73 op Donnie N4JZH
Michael A. Terrell
stated, Other than the filament rating, the internal structure is identical. I
sold a lot of 6KD6's for conversions at hamfests, and had hams bugging me for
more, for several years.
DavidC wrote:
> I recently asked about substitutes for the incredibly costly
> 8950 tube. I found a discussion on DejaNews about this and
> there was a suggestion that 6KG6A's are excellent.
>
> I looked closely at the facts and there seem to be several
> significant differences between the 8950 and all of the other
> suggested substitutes. I don't understand how a 6KD6 or
> 6KG6 could be "forced into" a 8950 tube socket.
>
> The 6KG6 is a Novar and I suppose the 6KD6 could fit in the
> 6KG6 socket but I don't think the 8950 is even close.
>
> I think maybe folks meant that after the amp was modified from an
> 8950 to a 6KG6 one could substitute a 6KD6 for the 6KG6.
>
> Can someone clarify please?
>
> - Thanks again & Happy Thanksgiving to all! DavidC K1YP
>
> **************************************************
>
Skipp comments on this guys post
:> have directly substituted without mods for the 8950?
: M2057.
:> Results?
: Works fine.
Would be the first time I've heard of a tube that directly crosses. The
M2057 is relatively unknown. You have a data sheet and source to look at?
A close cousin to the 8950 is the 6.3 volt heater 6HF5.
:> What tubes have you directly substituted for the 8950 with mods?
: 6LF6, 6MH6, 6LX6, 6KD6, 6JS6.
A lot of work I'm sure... I've done the classic swan mods from 6HF5 to
the 8950 which can be reversed. They are all similar, but require work. I
believe the 6HF5 is the closest cousin. Look at an old copy of the ARRL
Hints and Kinks Publication for the conversion.
:> What mods did you have to do?
: Filament rewiring and sometimes additional tank
: capacitance. If you're using the tall versions
: in an amp where the tubes are vertical, you have
: to lower the board or chassis where the tube
: sockets are and lengthen the plate leads. Some
: of the amps where the tubes are horizontal
: require mods to fit the longer tubes, and some
: won't work with the longer tubes at all. The
: long tubes are 5 inches long, and you need an
: eighth of an inch of clearance above the plate
: cap. The 6KG6/EL509 that's reasonably priced
: is one of the tall types.
Reads like he's actually done it, more by guessing... In supercathode
drive amplifiers (like Dentron and Amp Supply), the bias has to be
changed, the tube pins have to be routed to their proper functions.
Siltronix Radios used the 8950 in pentode high gain mode, the screen
voltage needs to be changed. The tank change in capacitance was not a big
deal. The bias and screen voltage was...
:> Results?
: They work fine.
If you really know what your doing... The EL-509 is a current production
from Svetlana. Kind of pricey, but so are the new-old-stock tubes. With
NOS sweep tubes, you will see slightly reduced gain vs the better 8950
operation values. The newer EL-509 and 519 might provide an attractive
retrofit.
:> I'm looking at modifying a Palomar 12v Amp designed for one 8950 driving
:> three and wish to make the mod that generates the maximum output that is
:> distortion and garbage-free using the existing power supply (changing caps
:> or other small components OK, changing transformers is not).
: None of the sweep tube amps are especially clean, so don't
: expect perfection when it comes to distortion. The crap
: content in sweep tube amps is usually 5 to 10 dB higher
: than in an equivalent ham amp that uses transmitting tubes.
Sounds like cannon fodder... what do you offer up as proof..? Sweep tube
amplifiers can be quite linear. Simple improvements (resistors in the
cathode leads) make them quite usable. My Amateur Sweep tube amplifiers
are very clean. I've measured the outputs.
: Personally, I wouldn't spend any money or time on a 12 volt
: tube amp. They're big, noisy, wasteful, unreliable, costly
: to repair, outdated piles in my opinion. I've had two 1-
: driving-3 sweep tube mobiles: a Palomar 310M, and a PAL
: 350MDX; I converted them both to base amps by gutting out
: the unreliable DC to DC power supplies and using 117CX
: Swan power supplies that are separate from the amp itself.
Time to learn something is never wasted...
What a waste of a classic mobile amplifer or two by you. Quite the work of
art to run an old Palomar Mobile Amplifier in your car. The old Palomar
300 drew 36 amps in transmit. Goodness it was glorious to drain a
battery with. Now he has boaring old converted base amps...
That inverter whine let you know things were honking along...
: The power supply connects to the amp through a jones plug
: (similar to the Palomar 300A design). With the stock
: power supply gone there's plenty of room for a fan to
: help keep the tubes from overheating.
A fan never hurt on top of any tube type mobile amplifier. Boaring mod,
you should have been able to make the mobile and base power supplies
operate the amp. Works out pretty well if you know what to do...
: If you're curious and just can't resist making that amp
: work, buy the cheapest tubes you can get ahold of, play
: with the amp until you've learned all you can, and then
: sell it for as much as you can. If the switching tran-
: sistors in the power supply are still good, and you didn't
: have to pay too much for the tubes, you may just be able
: to come close to breaking even when you sell it.
If you didn't lose your behind buying parts, you should be able to sell it
for a small profit providing it works well. If it works well for you and
makes you happy to run it, why sell it unless you want the bucks or
tradeup.
: If you need them, I have 6JS6As that will work in that
: amp (once you rewire the filaments) for $20 each. They
: are NOS, matched for gain (transconductance) RCAs in
: their original 1966 vintage boxes. The "A" version of
: the 6JS6 will produce as much power as an 8950, but has
Good price deal, but I don't believe the gain statement. Close maybe, but
not as much. How do you match the transconductance..? On a tube tester..?
Care to tell us how that can change at 28MHz..? Do you hi-pot test the
tubes for gas..?
: a lower plate dissipation spec. What that means is you
: have to be more careful when tuning the amp or the tubes
: will overheat.
Any amplifier for that matter... If your exceeding the tubes ratings at
anytime, something should be changed or your a gambling fool with money to
burn.
: When tuning the amp for the first time
: you should have the cover off so you can make sure the
: peak power output happens before the tuning caps reach
: either minimum or maximum capacitance. In other words,
: you want to make sure you can see both sides of the
: peak before the plates on the air-variable caps (there
: is one in the driver stage and two in the output stage)
: are either fully meshed (maximum capacitance) or fully
: unmeshed (minimum capacitance). If you don't do that
: there very often is a false peak at either the minimum
: or maximum capacitace position that makes you think
: the amp is properly tuned, when in reality the output
: isn't at maximum and the tubes are overheating because
: they have to dissipate too much power.
Looks like he's trying to describe tank circuit operation... If you've
got Pi-Net problems, more help is required. An ARRL Handbook is a good
place to start off. His description reads like the proper homework wasn't
done...
: Here's an applicable case history: I put a set of my
: 6JS6As in a Palomar Skipper 300. The Skipper 300 is a
: 1-driving-3 amp that is similar to the Palomar 310M
: mobile amp. When tuning it for the first time I saw
: both sides of the peak when tuning the driver cap, but
: both output stage caps ended up at their minimum capa-
: citance positions at what seemed to be maximum peak
: (modulated) output. The maximum peak output was about
: 550 watts (measured on a powered, peak-reading meter
: feeding a dummy load). I noticed that it only took
: about 10 seconds of key-down time before the tube plates
: began to glow. I knew the tubes wouldn't last long
: running like that. I experimented with different
: techniques to make the the output tank circuit (the
: two air-variable caps and the coil in between them)
: resonate with the caps near their half-meshed areas.
What was the drive mode, AM..? Drive Level..? Modulated or straight
carrier..?
Experimented..? Could have used the ARRL Handbook as a guide and figured
out what needed to be changed. A look at amplifier pi-nets would have been
in order. What were your "different techniques?"
: I didn't want to cut plates off of the caps, so I
: tried other things. In the end, adding 30 pF to the
: antenna load cap brought both caps back to near their
: half-meshed areas.
He changed the Q of the circuit and I'll be he doesn't know which
way it went. Wasn't the best way to go...
: In other words, I could see both
: sides of the peaks of both caps. The peak output
: went up to 620 watts and it takes 2 to 3 times more
: transmit time to make the tube plates glow. The amp
: went back into service and the customer is happy with
: it. The customer runs it on low (420 peak watts) to
: keep the tubes cool and his neighbors happy.
I don't know if I buy those numbers... Peak output as in peak carrier
power..? SSB operation with a big fan and low duty cycle maybe..? AM
continous operation..? I think not for any length of time at 100 duty
cycle.... Three or four tube sweep tube amplifer tubes will go
quickly go flat when you abuse them much.
:
:> Thanks for all who have already offered helpful info!
: You're welcome. I hope this helps.
:> 73, DavidC K1YP
: -=[Bill Eitner]=-
life goes on... hope he has spares.
cheers
sk...@pilot.ucdavis.edu
http://sonic.ucdavis.edu
Bill Eitner
>
> :> Now, can anyone tell me from direct personal experience what tubes they
> :> have directly substituted without mods for the 8950?
> : M2057.
> :> Results?
> : Works fine.
>
> Would be the first time I've heard of a tube that directly crosses. The
> M2057 is relatively unknown. You have a data sheet and source to look at?
I have a data listing for the tube. And besides,
anectdotal evidence is all that's necessary in
this case. The amplifiers in question are very
forgiving of minor differences in tube character-
istics.
> A close cousin to the 8950 is the 6.3 volt heater 6HF5.
The 6MH6 and the 6LF6 are the closest 6 volt
filament replacement for the 8950 and M2057.
> :> What tubes have you directly substituted for the 8950 with mods?
> : 6LF6, 6MH6, 6LX6, 6KD6, 6JS6.
>
> A lot of work I'm sure... I've done the classic swan mods from 6HF5 to
> the 8950 which can be reversed. They are all similar, but require work. I
> believe the 6HF5 is the closest cousin. Look at an old copy of the ARRL
> Hints and Kinks Publication for the conversion.
You're wrong about the 6HF5. It is not
as close a match to the 8950 as the 6LF6
and 6MH6. My info is from experience and
is backed up by the RCA Receiving Tube
Handbook.
> :> What mods did you have to do?
> : Filament rewiring and sometimes additional tank
> : capacitance. If you're using the tall versions
> : in an amp where the tubes are vertical, you have
> : to lower the board or chassis where the tube
> : sockets are and lengthen the plate leads. Some
> : of the amps where the tubes are horizontal
> : require mods to fit the longer tubes, and some
> : won't work with the longer tubes at all. The
> : long tubes are 5 inches long, and you need an
> : eighth of an inch of clearance above the plate
> : cap. The 6KG6/EL509 that's reasonably priced
> : is one of the tall types.
>
> Reads like he's actually done it, more by guessing... In supercathode
> drive amplifiers (like Dentron and Amp Supply), the bias has to be
> changed, the tube pins have to be routed to their proper functions.
What is that supposed to mean? I have actually
done it--so how could I be guessing? Your 6HF5
bullshit is an example of guesswork.
> Siltronix Radios used the 8950 in pentode high gain mode, the screen
> voltage needs to be changed. The tank change in capacitance was not a big
> deal. The bias and screen voltage was...
You're talking apples and oranges here. The amplifiers
in question are not like Siltronix (Swan) radios. The
amplifiers have very simple goals in their biasing.
Using similar yet different numbered tubes don't effect
those goals.
> :> Results?
> : They work fine.
>
> If you really know what your doing... The EL-509 is a current production
> from Svetlana. Kind of pricey, but so are the new-old-stock tubes. With
> NOS sweep tubes, you will see slightly reduced gain vs the better 8950
> operation values. The newer EL-509 and 519 might provide an attractive
> retrofit.
The current production 6KG6 falls into that catagory too.
I've posted info on that retrofit to this newsgroup several
times in the past.
> :> I'm looking at modifying a Palomar 12v Amp designed for one 8950 driving
> :> three and wish to make the mod that generates the maximum output that is
> :> distortion and garbage-free using the existing power supply (changing caps
> :> or other small components OK, changing transformers is not).
>
> : None of the sweep tube amps are especially clean, so don't
> : expect perfection when it comes to distortion. The crap
> : content in sweep tube amps is usually 5 to 10 dB higher
> : than in an equivalent ham amp that uses transmitting tubes.
>
> Sounds like cannon fodder... what do you offer up as proof..?
My own spectrum analysis results.
> Sweep tube
> amplifiers can be quite linear. Simple improvements (resistors in the
> cathode leads) make them quite usable. My Amateur Sweep tube amplifiers
> are very clean. I've measured the outputs.
My statement was a generalization. You have an amateur
sweep tube amp, so you're going to defend it based on
that fact alone. Your objectivity in this situation is
suspect.
> : Personally, I wouldn't spend any money or time on a 12 volt
> : tube amp. They're big, noisy, wasteful, unreliable, costly
> : to repair, outdated piles in my opinion. I've had two 1-
> : driving-3 sweep tube mobiles: a Palomar 310M, and a PAL
> : 350MDX; I converted them both to base amps by gutting out
> : the unreliable DC to DC power supplies and using 117CX
> : Swan power supplies that are separate from the amp itself.
>
> Time to learn something is never wasted...
> What a waste of a classic mobile amplifer or two by you. Quite the work of
> art to run an old Palomar Mobile Amplifier in your car. The old Palomar
> 300 drew 36 amps in transmit. Goodness it was glorious to drain a
> battery with. Now he has boaring old converted base amps...
> That inverter whine let you know things were honking along...
Nice troll.
> : The power supply connects to the amp through a jones plug
> : (similar to the Palomar 300A design). With the stock
> : power supply gone there's plenty of room for a fan to
> : help keep the tubes from overheating.
>
> A fan never hurt on top of any tube type mobile amplifier. Boaring mod,
> you should have been able to make the mobile and base power supplies
> operate the amp. Works out pretty well if you know what to do...
Yeah, right.
> : If you're curious and just can't resist making that amp
> : work, buy the cheapest tubes you can get ahold of, play
> : with the amp until you've learned all you can, and then
> : sell it for as much as you can. If the switching tran-
> : sistors in the power supply are still good, and you didn't
> : have to pay too much for the tubes, you may just be able
> : to come close to breaking even when you sell it.
>
> If you didn't lose your behind buying parts, you should be able to sell it
> for a small profit providing it works well. If it works well for you and
> makes you happy to run it, why sell it unless you want the bucks or
> tradeup.
Chances are, once he hears that horrid sound it makes,
he'll want rid of it.
> : If you need them, I have 6JS6As that will work in that
> : amp (once you rewire the filaments) for $20 each. They
> : are NOS, matched for gain (transconductance) RCAs in
> : their original 1966 vintage boxes. The "A" version of
> : the 6JS6 will produce as much power as an 8950, but has
>
> Good price deal, but I don't believe the gain statement. Close maybe, but
> not as much.
Plenty enough to produce full output.
> How do you match the transconductance..? On a tube tester..?
Yes.
> Care to tell us how that can change at 28MHz..?
Frequency of operation is irrelevent in this
situation.
> Do you hi-pot test the
> tubes for gas..?
No. You can do that in a working circuit.
Say what you will, but I'm not going on the defensive
over your trolling.
>
> : a lower plate dissipation spec. What that means is you
> : have to be more careful when tuning the amp or the tubes
> : will overheat.
>
> Any amplifier for that matter... If your exceeding the tubes ratings at
> anytime, something should be changed or your a gambling fool with money to
> burn.
Thank you for re-stating the obvious.
> : When tuning the amp for the first time
> : you should have the cover off so you can make sure the
> : peak power output happens before the tuning caps reach
> : either minimum or maximum capacitance. In other words,
> : you want to make sure you can see both sides of the
> : peak before the plates on the air-variable caps (there
> : is one in the driver stage and two in the output stage)
> : are either fully meshed (maximum capacitance) or fully
> : unmeshed (minimum capacitance). If you don't do that
> : there very often is a false peak at either the minimum
> : or maximum capacitace position that makes you think
> : the amp is properly tuned, when in reality the output
> : isn't at maximum and the tubes are overheating because
> : they have to dissipate too much power.
>
> Looks like he's trying to describe tank circuit operation... If you've
> got Pi-Net problems, more help is required. An ARRL Handbook is a good
> place to start off. His description reads like the proper homework wasn't
> done...
More trolling.
> : Here's an applicable case history: I put a set of my
> : 6JS6As in a Palomar Skipper 300. The Skipper 300 is a
> : 1-driving-3 amp that is similar to the Palomar 310M
> : mobile amp. When tuning it for the first time I saw
> : both sides of the peak when tuning the driver cap, but
> : both output stage caps ended up at their minimum capa-
> : citance positions at what seemed to be maximum peak
> : (modulated) output. The maximum peak output was about
> : 550 watts (measured on a powered, peak-reading meter
> : feeding a dummy load). I noticed that it only took
> : about 10 seconds of key-down time before the tube plates
> : began to glow. I knew the tubes wouldn't last long
> : running like that. I experimented with different
> : techniques to make the the output tank circuit (the
> : two air-variable caps and the coil in between them)
> : resonate with the caps near their half-meshed areas.
>
> What was the drive mode, AM..? Drive Level..? Modulated or straight
> carrier..?
> Experimented..? Could have used the ARRL Handbook as a guide and figured
> out what needed to be changed. A look at amplifier pi-nets would have been
> in order. What were your "different techniques?"
You're just envious as Hell of me aren't you?
> : I didn't want to cut plates off of the caps, so I
> : tried other things. In the end, adding 30 pF to the
> : antenna load cap brought both caps back to near their
> : half-meshed areas.
>
> He changed the Q of the circuit and I'll be he doesn't know which
> way it went. Wasn't the best way to go...
It's a mono-band amp--the Q is irrelevant--just like
your trolling.
> : In other words, I could see both
> : sides of the peaks of both caps. The peak output
> : went up to 620 watts and it takes 2 to 3 times more
> : transmit time to make the tube plates glow. The amp
> : went back into service and the customer is happy with
> : it. The customer runs it on low (420 peak watts) to
> : keep the tubes cool and his neighbors happy.
>
> I don't know if I buy those numbers...
That's your problem.
> Peak output as in peak carrier
> power..? SSB operation with a big fan and low duty cycle maybe..? AM
> continous operation..? I think not for any length of time at 100 duty
> cycle.... Three or four tube sweep tube amplifer tubes will go
> quickly go flat when you abuse them much.
More re-stating of the obvious.
> :
> :> Thanks for all who have already offered helpful info!
> : You're welcome. I hope this helps.
> :> 73, DavidC K1YP
> : -=[Bill Eitner]=-
>
> life goes on... hope he has spares.
> cheers
> sk...@pilot.ucdavis.edu
> http://sonic.ucdavis.edu
Bye-bye troll.
Sean
everything is dialed in correctly. They are also WAY more money and even
harder to find. Sean
>
Skipp comments on this guys post wrote in message
<81vqhi$1a6$7...@mark.ucdavis.edu>...
Fresh air for the tired 8950 thread
: The M2057 is a direct drop in for the 8950 and will EASILY outperform it if
: everything is dialed in correctly. They are also WAY more money and even
: harder to find. Sean
Hi Sean,
So who made the M2057 and where can we find them..? Any idea what they
sell for..?
thanks
sk...@pilot.ucdavis.edu
Toll Free
if
> : everything is dialed in correctly. They are also WAY more money and
even
> : harder to find. Sean
>
> So who made the M2057
Most of the companies that made tubes made the M2057, although the ECG /
Phillips seem to do best in RF.
and where can we find them..?
You really can't.
Any idea what they
> sell for..?
Over a hundred dollars a piece.
Toll Free
>
> thanks
> sk...@pilot.ucdavis.edu
>
Put this 8950 thread to bed at last
We keep running into each other... Thanks for the tube availability info.
We can sum up the M2057 by saying Bill didn't offer up any type of
reasonable substitute if the tube isn't really available anymore.
Bill also offered up some pretty faulty amplifier hack information. One
would do much better to Pick up a copy of the ARRL Handbook and pour
through the real McCoy about amplifier pinet operation.
I'm also not surprised to receive a few Newsgroup Reader Emails telling me
Bill has been cited by the FCC and had his Ham ticket taken away... Any
truth to that Bill. I just think his faulty information might do damage
and ruin the fun for others.
cheers
sk...@pilot.ucdavis.edu
: Toll Free <toll...@bigradios.com> wrote:
:> So who made the M2057
The Landshark
>
> The M2057 is a direct drop in for the 8950 and will EASILY outperform it if
> everything is dialed in correctly. They are also WAY more money and even
> harder to find. Sean
>
Nice to hear from ya Sean, Merry Christmas & Happy New year
in advance............
The Landshark
--
"Ah it's a Buell-tiful day for a perfect ride"
98 Buell S3 Thunderbolt
83 Honda 1100F
99 Ford F150 Supercab
rffl...@gmail.com
doncar...@gmail.com
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lu3...@gmail.com
LU3AGI
lu3...@gmail.com
> 8950 tube. I found a discussion on DejaNews about this and
> there was a suggestion that 6KG6A's are excellent.
>
> I looked closely at the facts and there seem to be several
> significant differences between the 8950 and all of the other
> suggested substitutes. I don't understand how a 6KD6 or
> 6KG6 could be "forced into" a 8950 tube socket.
>
> The 6KG6 is a Novar and I suppose the 6KD6 could fit in the
> 6KG6 socket but I don't think the 8950 is even close.
>
> I think maybe folks meant that after the amp was modified from an
> 8950 to a 6KG6 one could substitute a 6KD6 for the 6KG6.
>
> Can someone clarify please?
>
> - Thanks again & Happy Thanksgiving to all! DavidC K1YP
>
> **************************************************
>
>
>
>
> * Sent from RemarQ http://www.remarq.com * The Internet's Discussion Network *
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tramdr
The M-2057 is the military or heavy duty or ruggedized verion of the 8950. It is the same tube and pinout, but it is bigger and heavier. Since it is physically and electrically bigger, it is not quite a direct drop in. It does use the same 12v filament for one, but it draws a bit more filament current than the 8950. The capacitances would be somewhat off from an 8950 too. It will take more abuse, take more voltage and put out more than an 8950 but it is somewhat different.
Here's a clip and paste of a tube chart I made of the 12 pin sweep tube:
12 PIN large (Palomar Maco)
6LF6 40 6V 2A
6LX6 40 6LF6, 6LX6, and 6MH6 are said to be virtually identical except for size
6MH6 38.5
6JS6 28
6JS6A 28
6JS6B 28
6JS6C 30
6KD6 33
6KN6* 30
6LB6 30
6LR6 30
6JM6A 17.5
8950 33 12V Filament 1.1A
M2057 40 12V Filament 1.3A