If things get really tough, try what I've done. I have some 12JB6's and
some 18JB6's. The final filaments can be re-directed and run via an
external xformer. It works fine. However, I just bit the bullet and
bought several pairs from reasonable sources. Given the number of hours
I use the Drake C-line each month or year, I'm sure I'll be OK until I
"check out of the net".....

Noone has raised the issue of how long 6JB6s last.

If they are used with caution they last for a long time, but if one =
tries to squeeze the last watt out of them (and the 6JB6s invite you to =
do so, thanks to their strong cathode emission) they can last for a VERY =
short time.

The 6146 have a lower cathode emission and do not then lend themsleves =
to be squeezed so badly as the 6JB6s. So there is less harm to =
inadvertently destroy them.

To my experience the Sylvania 6JB6s (those sold by Drake as spares) =
perform better than the GE 6JB6s, and are are easier to neutralize. The =
RCA 6JB6s, luckily much less common, were no good.

73

Tony, I0JX

------------------------------------------------------
Antonio Vernucci, I0JX US call: K0JX
50-MHz beacon: 50.004 KHz FSK 10W 5/8 vertical antenna
home page: http://www.qsl.net/i0jx
e-mail: k0jx {at} amsat {dot} org
------------------------------------------------------
"RadioGuy" ha scritto nel messaggio =
...
The thought came to me the other day whle thinking about the cost of =
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at =
AES back
in the 1970's and I got plenty of spares. Why did Drake use those =
cheap ass
sweep tubes in their final instead of the old standard 6146 to begin =
with?
=20
Sure, back then it seemed in vogue to use sweep tubes in amateur gear =
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda =
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.
=20
(Yes... I have a complete Drake station (including amplifier)---the =
whole
line-up in pristine, vitrually unused condition in crisp factory =
cartons
including accessories, catalogs and a handful of the right-angle =
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)
=20
RG
=20

Antonio Vernucci wrote in message
...
Noone has raised the issue of how long 6JB6s last.

If they are used with caution they last for a long time, but if one tries to
squeeze the last watt out of them (and the 6JB6s invite you to do so, thanks
to their strong cathode emission) they can last for a VERY short time.

The 6146 have a lower cathode emission and do not then lend themsleves to be
squeezed so badly as the 6JB6s. So there is less harm to inadvertently
destroy them.

To my experience the Sylvania 6JB6s (those sold by Drake as spares) perform
better than the GE 6JB6s, and are are easier to neutralize. The RCA 6JB6s,
luckily much less common, were no good.

73

Tony, I0JX

Absolutely Tony... I share the same experiences as you. I've recently
listened to the youngsters getting their hands on the Drakes but not knowing
how to tune the pi-network with the consequence that they destroy the 6JB6's
in short order---and having to put out $100 for another set. Those sweep
tubes weren't very forgiving... If I remember, we never really worried
about hurting the 6146's as they seemed to keep on working. Furthermore,
correct me if I am wrong, I don't think we ever considered having matched
6146's like we did with the sweep tubes.

RG

Its very simple. POWER sells. Sweep tubes have that extra output for the
bigger price tag. A $9.00 sweep tube in the 70's cost a dealer $3.00. Cant
imagine what the low cost would be to a manufacturer. Bottom line for all
companies......PROFIT.......PROFIT........PROFIT.

--
Regards,
Gary...
"RadioGuy" wrote in message
...
The thought came to me the other day whle thinking about the cost of
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at AES
back
in the 1970's and I got plenty of spares. Why did Drake use those cheap
ass
sweep tubes in their final instead of the old standard 6146 to begin with?

Sure, back then it seemed in vogue to use sweep tubes in amateur gear
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.

(Yes... I have a complete Drake station (including amplifier)---the whole
line-up in pristine, vitrually unused condition in crisp factory cartons
including accessories, catalogs and a handful of the right-angle
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)

RG

"RadioGuy" wrote in message
...
The thought came to me the other day whle thinking about the cost of
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at AES
back
in the 1970's and I got plenty of spares. Why did Drake use those cheap
ass
sweep tubes in their final instead of the old standard 6146 to begin with?

Sure, back then it seemed in vogue to use sweep tubes in amateur gear
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.

(Yes... I have a complete Drake station (including amplifier)---the whole
line-up in pristine, vitrually unused condition in crisp factory cartons
including accessories, catalogs and a handful of the right-angle
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)

RG


When the Drake vacuum tubes rigs were designed, the sweep tubes were being
mass produced for the TV market and WERE very cheap.

However, there may have been another reason.
If I remember correctly, the advertised power output of the TR3/TR4 and the
T4X, etc was higher than the 180 watts input/100 watts output that was
typical from a pair of 6146's. A pair or trio of sweep tubes is capable of
a much high PEP rating than is a pair of 6146's - albeit maybe not for
long....


Thus there was a marketing race at the time.
Each manufacturer was claiming higher and higher power levels for their
"bareful" rigs.
Swan was surely the champ with that - claiming up to 700 watts input and
about 500 watts output for some of their rigs.
Drake didn't go so far but probably still wanted to claim more power than
the 180 watts input/100 watts output of Collins and Heathkit.

National also used sweep tubes in their transceivers. For example, they used
the 6GJ5 in their NCX-3 and the NCX-5 and at first were conservative with
their rating, also claiming just 180 watts in/about 100 watts out. Later
they joined the PEP race with their NCX-500, etc.

Thus part of the answer may simply be marketing.

73,

Doug/WA1TUT

DOUGLAS wrote in message
k.net...

"RadioGuy" wrote in message
...
The thought came to me the other day whle thinking about the cost of
6JB6's
nearly $100 for a set; I paid $18.00 for a matched set of three at AES
back
in the 1970's and I got plenty of spares. Why did Drake use those cheap
ass
sweep tubes in their final instead of the old standard 6146 to begin
with?

Sure, back then it seemed in vogue to use sweep tubes in amateur gear
(yea,
sure, Swan gear...) but as I recall, we thought that Drake was kinda
cheesy
to use those tubes anyway. I gonna stick my neck out and say Drake
engineering wasn't the end all that the youngsters think nowadays.

(Yes... I have a complete Drake station (including amplifier)---the
whole
line-up in pristine, vitrually unused condition in crisp factory cartons
including accessories, catalogs and a handful of the right-angle
Switchcraft
microphone (black cap) and key (red cap) plugs that Drake originally
supplied not that PL-whatever. Original owner---me---so it's not sour
grapes.)

RG


When the Drake vacuum tubes rigs were designed, the sweep tubes were being
mass produced for the TV market and WERE very cheap.

However, there may have been another reason.
If I remember correctly, the advertised power output of the TR3/TR4 and
the
T4X, etc was higher than the 180 watts input/100 watts output that was
typical from a pair of 6146's. A pair or trio of sweep tubes is capable
of
a much high PEP rating than is a pair of 6146's - albeit maybe not for
long....


Thus there was a marketing race at the time.
Each manufacturer was claiming higher and higher power levels for their
"bareful" rigs.
Swan was surely the champ with that - claiming up to 700 watts input and
about 500 watts output for some of their rigs.
Drake didn't go so far but probably still wanted to claim more power than
the 180 watts input/100 watts output of Collins and Heathkit.

National also used sweep tubes in their transceivers. For example, they
used
the 6GJ5 in their NCX-3 and the NCX-5 and at first were conservative with
their rating, also claiming just 180 watts in/about 100 watts out. Later
they joined the PEP race with their NCX-500, etc.

Thus part of the answer may simply be marketing.

73,

Doug/WA1TUT

Well said Doug... I forgot about that---there was a power race back in the
70's. Some of us did get 'big eyes' when Swan came out with the 500. And
now that you mentioned it, I remember some of us looking at the Drake's 300
watt (input) tranceiver as a selling point ( I think the power race ended
somewhat with the advent of solidstate and the fairly uniform 100 watt
specification).

Drake had a problem meeting their power claim later for the TR-4C/CW/CW+RIT
(I don't know about the older models), resulting from the changes to FCC
regs regarding spectral purity (97.73). Drake had a notice that the final
could not be loaded to more that 350 ma. so as to remain within the new
spec. The older tune-up procedure reached maximum output with a plate
current of 380 to 500 ma. I am not going to venture to say if the 6JB6's
had anything to do with having to go to a reduced output as opposed to using
the 6146's in their place regarding spectral purity but I sure would like to
hear comments on this point.

I like the note in the operators manual regarding tune-up:

3-7. TUNE UP. Do not allow plate current to exceed 0.1 Amperes for more
that 6 seconds with the PLATE control not tuned for minimum plate current or
maximum output.

CAUTION Failure to observe the warning above will result in rapid final
amplifier tube deterioration due to excessive plate dissipation.

RG