Is EL84/6BQ5 = 7189? (possible misrepresentation)
davefr
are strong vintage Zenith 7189".
The amp actually had 4 - Zenith output tubes market 6BQ5/EL84. And
they tested very strong.
It appears that Scott 222's with 6BQ5's were rated at 15 watts, yet
with 7189's were rated at 24 watts. Is the difference just the tubes
or the whole design with "beefier" output Xformers?
The seller otherwise represented the item very accurately and was a
pleasure to deal with.
Was I kind of screwed or is this just a nit. I kind of want to leave
the seller positive feedback because it's in excellent cond.
otherwise. Triode's web site kind of lumps all three of these tubes
in the same bucket.
Thanks!!
OvrReactor
identical to a 6BQ5, except that a 7189 is rated to handle higher plate/screen
dissipation, and higher plate/screen voltage than the 6BQ5.
You can substitute a 7189 into a socket that calls for a 6BQ5, but you CAN'T
sub a 6BQ5 into a socket that calls for a 7189......UNLESS the B+ is low enough
to allow it.
Regards,
Tom Mitchell
hitu...@my-deja.com
plates,and I had the cover off so I could watch them when I was running
it.I would find out what a quad of used 6BQ5s marked Zenith are worth
and subtract that from what the price of a Matched quad of Sovteck
7189s delivered is and tell the seller that he mislead you and give him
some options.The 6BQ5s will fry and could cause damage.Could take a
while,but that pretty blue glow means the voltage is to high.I hope
those "Zeniths" are marked made in USA .
David Thatcher
Sent via Deja.com http://www.deja.com/
Before you buy.
Tim Reese
#are strong vintage Zenith 7189".
#
#The amp actually had 4 - Zenith output tubes market 6BQ5/EL84. And
#they tested very strong.
#
#It appears that Scott 222's with 6BQ5's were rated at 15 watts, yet
#with 7189's were rated at 24 watts. Is the difference just the tubes
#or the whole design with "beefier" output Xformers?
#
#The seller otherwise represented the item very accurately and was a
#pleasure to deal with.
#
#Was I kind of screwed or is this just a nit. I kind of want to leave
#the seller positive feedback because it's in excellent cond.
#otherwise. Triode's web site kind of lumps all three of these tubes
#in the same bucket.
#
#Thanks!!
#
#In article <19990928043220...@ng-fw1.aol.com>,
#OvrReactor <ovrre...@aol.com-nospam> wrote:
#>I can't tell you anything about the Scott's, but i CAN tell you that a 7189 is
#>identical to a 6BQ5, except that a 7189 is rated to handle higher plate/screen
#>dissipation, and higher plate/screen voltage than the 6BQ5.
#>
#>You can substitute a 7189 into a socket that calls for a 6BQ5, but you CAN'T
#>sub a 6BQ5 into a socket that calls for a 7189......UNLESS the B+ is low enough
#>to allow it.
#>
#>Regards,
#>Tom Mitchell
#
Just to add a bit to Tom's reply, the plate voltage of the 222C is about
420V with fixed bias, much higher than the 6BQ5s plate voltage rating. NOS
(new old-stock) US 6BQ5s can generally be subbed for 7189s and not fail,
but they wear out rather quickly - I ran Phillips ECG 6BQ5s in my 222C and
they lasted for about 1.5 years of heavy service.
Using 6BQ5s instead of 7189s won't change the power output of the amp, but
the tubes will be operated at higher dissipation than they are rated for.
The 222 runs a lower plate voltage than the 222C, thus the lower power
rating.
Triode offers the 7189/EL84M which works well in the 222C at ca $50/quad;
this is what my 222C uses currently. All the rest (Tesla, Yugo, Russian)
are 6BQ5s and unsuitable.
hth tr
--
----------------------------------------------------------------------
Tim Reese, MGH NMR Center re...@nmr.MGH.harvard.edu
OvrReactor
I figured that was the difference in the two Scotts, but I didn't want to just
go shooting off at the virtual mouth by guessing that the 7189 fitted Scott had
a higher B+ than the 6BQ5 model. I'm a guitar amp guy after all, and we're
supposed to be know-nothing bumpkins.
Best Regards,
Tom Mitchell
Punkerdubh
davefr <dav...@REMOVETHISpacifier.com> wrote in message
news:37f01d6a...@news.giganews.com...
> I bought a Scott 222C on EBAY. The description said "The output tubes
Hey, I was bidding on that one, but wasn't able to get online when
the auction was closing, and you (and a few others) outbid me.
Congratulations on the purchase, it looks like a fine piece. How
do you like the sound? Anyways, as others in this thread have
pointed out, 6BQ5's really aren't *supposed* to be used here, but
many NOS ones will work fine. I'd just get a backup quad of the
EL84M (Tesla?) and run the Zeniths until the conk out.
Enjoy the amp,
- Punkerdubh
John Byrns
re...@larmor.nmr.mgh.harvard.edu (Tim Reese) wrote:
My tube manual specs both the 7189 and the 6BQ5 at 12 Watts plate
dissipation, only the Voltage ratings are higher on the 7189.
With respect to the Scott 222 and 222C, it wouldn't surprise me at all if
the plate dissipation at idle is higher in the 222(b), than it is in the
222C. That's just a seat of the pants guess, I would have to calculate it
to be sure. The 222(B) uses cathode bias, and while the plate Voltage is
lower, due to both a lower supply Voltage, and the loss across the cathode
"resistor", the 222(B) runs the 6BQ5's at a much higher idle current than
does the fixed bias 222C.
Regards,
John Byrns
Surf my web pages at, http://www.enteract.com/~jbyrns/index.html
Tim Reese
Maybe I'm the bumpkin here - my point about the increased dissipation is
apparently wrong. His post hasn't shown up on the Harvard server yet, but
John Byrnes points out that the dissipation of the 6BQ5 and the 7189 are both
12W ... so John, where does the higher power rating come from - fixed bias?
humbly tr
John Byrns
re...@larmor.nmr.mgh.harvard.edu (Tim Reese) wrote:
> In article <19990928132725...@ng-ci1.aol.com>,
> OvrReactor <ovrre...@aol.com-nospam> wrote:
> >>the plate voltage of the 222C is about 420V with fixed bias
> >
> >I figured that was the difference in the two Scotts, but I didn't want
to just
> >go shooting off at the virtual mouth by guessing that the 7189 fitted
Scott had
> >a higher B+ than the 6BQ5 model. I'm a guitar amp guy after all, and we're
> >supposed to be know-nothing bumpkins.
> >
> >Best Regards,
> >Tom Mitchell
>
> Maybe I'm the bumpkin here - my point about the increased dissipation is
> apparently wrong. His post hasn't shown up on the Harvard server yet, but
> John Byrnes points out that the dissipation of the 6BQ5 and the 7189 are both
> 12W ... so John, where does the higher power rating come from - fixed bias?
Yes, both fixed bias, and the fact that the 222C(D) doesn't need to run a
high idle current to heat the preamp tube heaters, allowing a higher B+
supply Voltage, results in the higher power output.
The fixed bias allows the 222C(D) to run deeper in class AB, with a higher
plate Voltage, and lower idle current, for a higher power output. The
closer you can get to class B operation, to more power you can get out of
a given pair of tubes. The 222(B) uses cathode bias, and because of bias
shift, can't run as deep in class AB, also the 222(B) must run a rather
high idle current to heat the preamp tube heaters which are in the cathode
circuit of the output tubes. Even if the 222(B) had fixed bias, the
higher idle current would mean that the amp was running closer to class A
operation, which means a lower maximum power output.
Gabe Velez
Tim Reese wrote:
> Maybe I'm the bumpkin here - my point about the increased dissipation is
> apparently wrong. His post hasn't shown up on the Harvard server yet, but
> John Byrnes points out that the dissipation of the 6BQ5 and the 7189 are both
> 12W ... so John, where does the higher power rating come from - fixed bias?
>
> humbly tr
I do not have the specs in front of me, bt i do believe that you are correct. I
do happen to have a lot of experience with the 6BQ5/EL84/7189 family and in my
search for the best one for the job found that the 6BQ5/EL84 has a 300 volt plate
rating, at 12 watts dissipation, where the 7189 has a 400 volt plate rating at 12
watts dissipation. So, the 7189 could be driven to 12 watts with better longevity
for the 24 watt output rating than the 6BQ5, likely because of the higher voltage
rating. The 7189-A has a 13.5 watt dissipation.
I had the pleasure of being able to get 7189-A's for my first tube amp way back
when tubes were still available and tube testers were still in local pharmacies (the
'70's).
I may be wrong but not much. I will double check tonight. The 7189 is, if memory
serves, a military version 6BQ5, where the EL84 is the European version.
--
Have Fun!
Gabe
Gabe's Tubes 'n' Stuff
Brian McAllister
<gve...@richmond.infi.net> wrote:
>
> I may be wrong but not much. I will double check tonight. The 7189 is, if memory
>serves, a military version 6BQ5, where the EL84 is the European version.
Actually, I think that 6BQ5 is the American version of the EL84. I
don't recall seeing US made ones until after the EL84 had been out for
quite a while.
Brian McAllister
Durham NC
Vintage Radio and Audio Web Pages
http://mcallister.simplenet.com
Steve Robertson
manufactured) and 6BQ5 (U.S. Designator) are supposed to be true pentodes. The 7189 (U.S.
"industrial" designator) is electrically similar but is a beam tetrode. Supposedly to get
a bit more power out at a higher plate voltage and often with fixed bias, the 7189 was
designed. The article also stated, I believe, that some U.S. branded 6BQ5 were also beam
tubes (maybe to avoid a royalty payment??)..
Bottom line, 7189 should work anywhere an EL84/6BQ5 is specified, but EL84/6BQ5 may or
may not work where a 7189 is specified.
I have several EL84/6BQ5 amps that are designed to run 360v plate and screen voltage
(which is way over the stated 300v max) with no problems. This is with recent Tesla/JJ
and Sovtek as well as a variety of old used U.S. and Japanese versions.
The Sovtek EL84M is supposed to be able to take the higher voltages that 7189 can (over
400v). I don't have any amps that get up there, so I haven't tried them. However, if it
means anything, I'm using Sovtek EL84 in an amp and am very pleased with the sonics and
the longevity.
Best regards,
Steve Robertson
rober...@saic.com
Darryl
You were saying......
>I have several EL84/6BQ5 amps that are designed to run 360v plate and screen voltage
>(which is way over the stated 300v max) with no problems. This is with recent Tesla/JJ
>and Sovtek as well as a variety of old used U.S. and Japanese versions.
Yes, the Pioneer amp i have just (almost finished) restored uses 360v
in it's El84 PP output stage. I have had Sovtek, Telefunken, Hitachi,
Tesla and one unknown in there and all survive quite well. (The
Hitachi's were the originals - that's nearly 40 years old)
__ \ \ __ /__ / \
| | _ \ / / _ \
| | ___ \ / / ___ \
____/_/ _\____|____|_/ _\
Gabe Velez
Darryl wrote:
> Hi Steve Robertson,
>
> You were saying......
>
> >I have several EL84/6BQ5 amps that are designed to run 360v plate and screen voltage
> >(which is way over the stated 300v max) with no problems. This is with recent Tesla/JJ
> >and Sovtek as well as a variety of old used U.S. and Japanese versions.
>
> Yes, the Pioneer amp i have just (almost finished) restored uses 360v
> in it's El84 PP output stage. I have had Sovtek, Telefunken, Hitachi,
> Tesla and one unknown in there and all survive quite well. (The
> Hitachi's were the originals - that's nearly 40 years old)
Same Here. My old Magnavox states a voltage of 350 at the plates (I have the Sams for
it). Actual measurement was about 330. Before I tinkered with it the original BQ5's were
still in there. Thta is 18 yeas without a hitch. So, I guess Tim (I think he said his
lasted 1.5 years) has an amp that idles at too high a current. In My amp, recently
redesigned using the old magnavox circuit, idles at 32 milliamps each tube. With 310 volts
at the plates that means that they are idling at 9 watts. Not bad. It is within spec. And I
am using JJ/Teslas. They sound real nice. Oh, that original Magnavox saw at *least* 5 hours
a day duty. It was part of a console TV. 5*365*18=32850 hours. That is a testimony to the
longevity of tubes, and the quality of manufacture of those days (Not to mention the
excessive viewing of TV! ;-) ).
Well, enough of my ranting.
RGray19520
voltage. The two tubes that are built today are so similar that i doubt are
different at all except the branding
Richard Gray
Audio Line Source
Darryl
You were saying......
> Same Here. My old Magnavox states a voltage of 350 at the plates (I have the Sams for
>it). Actual measurement was about 330.
Mine actually measured 360, even before recapping.
>Before I tinkered with it the original BQ5's were
>still in there. Thta is 18 yeas without a hitch. So, I guess Tim (I think he said his
>lasted 1.5 years) has an amp that idles at too high a current.
Exactly. The high voltage on it's own won't kill them (provided they
don't arc over or something (which they don't).
>In My amp, recently
>redesigned using the old magnavox circuit, idles at 32 milliamps each tube. With 310 volts
>at the plates that means that they are idling at 9 watts. Not bad. It is within spec. And I
>am using JJ/Teslas. They sound real nice. Oh, that original Magnavox saw at *least* 5 hours
>a day duty. It was part of a console TV. 5*365*18=32850 hours. That is a testimony to the
>longevity of tubes, and the quality of manufacture of those days (Not to mention the
>excessive viewing of TV! ;-) ).
Hehe. I have bravely put mine into the main entertainment system in
our house. This means that the Pioneer gets used as the front
channels of a small surround sound system when I'm not playing CD's or
vinyl. The EL84's are gonna clock up some hours, but hey, they're a
cheap valve. The matched quad Tesla's I got from Ned are nice sounding
as well. (free plug !)
Steven L. Bender
Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
Tue, 28 Sep 1999 02:04:11 GMT
I bought a Scott 222C on EBAY. The description said "The output tubes
are strong vintage
Zenith 7189".
The amp actually had 4 - Zenith output tubes market 6BQ5/EL84. And they
tested very
strong.
It appears that Scott 222's with 6BQ5's were rated at 15 watts, yet
with 7189's were rated at
24 watts. Is the difference just the tubes or the whole design with
"beefier" output Xformers?
The seller otherwise represented the item very accurately and was a
pleasure to deal with.
Was I kind of screwed or is this just a nit. I kind of want to leave
the seller positive feedback
because it's in excellent cond. otherwise. Triode's web site kind of
lumps all three of these
tubes in the same bucket.
Thanks!!
-- 6BQ5's that are NOS, are identical to 7189's in EVERY WAY.
The fact that 7189's were rated for a higher voltage than 6BQ5's
just goes to show that 6BQ5's could be rated for higher voltage
too, but simply weren't for reasons that had nothingv to do with
reality.
- SB.
Article:
2 of 9
From:
OvrReactor <ovrre...@aol.com-nospam>
Subject:
Re: Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
28 Sep 1999 08:32:20 GMT
I can't tell you anything about the Scott's, but i CAN tell you that a
7189 is identical to a
6BQ5, except that a 7189 is rated to handle higher plate/screen
dissipation, and higher
plate/screen voltage than the 6BQ5.
You can substitute a 7189 into a socket that calls for a 6BQ5, but you
CAN'T sub a 6BQ5
into a socket that calls for a 7189......UNLESS the B+ is low enough to
allow it.
Regards, Tom Mitchell
-- Both tubes have equal Pd ratings.
- SB.
Article:
3 of 9
From:
Tim Reese <re...@larmor.nmr.mgh.harvard.edu>
Subject:
Re: Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
28 Sep 1999 11:11:08 -0400
I bought a Scott 222C on EBAY. The description said "The output
tubes are strong
vintage Zenith 7189".
The amp actually had 4 - Zenith output tubes market 6BQ5/EL84. And
they tested very
strong.
It appears that Scott 222's with 6BQ5's were rated at 15 watts, yet
with 7189's were rated
at 24 watts. Is the difference just the tubes or the whole design
with "beefier" output
Xformers? The seller otherwise represented the item very accurately
and was a pleasure
to deal with.
Was I kind of screwed or is this just a nit. I kind of want to leave
the seller positive
feedback because it's in excellent cond. otherwise. Triode's web
site kind of lumps all
three of these tubes in the same bucket.
Thanks!!
In article <19990928043220...@ng-fw1.aol.com>,
OvrReactor
<ovrre...@aol.com-nospam> wrote:
I can't tell you anything about the Scott's, but i CAN tell you
that a 7189 is identical to
a 6BQ5, except that a 7189 is rated to handle higher plate/screen
dissipation, and
higher plate/screen voltage than the 6BQ5. You can substitute a
7189 into a socket
that calls for a 6BQ5, but you CAN'T sub a 6BQ5 into a socket that
calls for a
7189......UNLESS the B+ is low enough to allow it.
Regards,
Tom Mitchell
Just to add a bit to Tom's reply, the plate voltage of the 222C is
about 420V with fixed bias,
much higher than the 6BQ5s plate voltage rating. NOS (new old-stock) US
6BQ5s can
generally be subbed for 7189s and not fail, but they wear out rather
quickly - I ran Phillips
ECG 6BQ5s in my 222C and they lasted for about 1.5 years of heavy
service.
Using 6BQ5s instead of 7189s won't change the power output of the amp,
but the tubes will
be operated at higher dissipation than they are rated for. The 222 runs
a lower plate voltage
than the 222C, thus the lower power rating.
-- USING Tubes above their rated voltage and dissipation will fry them
relatively quickly.
Still, best to keep the voltages down, on all small [power tubes. Current
AC line voltages
are about 15 volts higher than when most older tube sets were made in the
1960's, so the
Plate voltages will tend to be 10% to 15% higher today... OTOH, I've run
10BQ5's ( 6BQ5 with a
different filament ) at 270 volts and 154 mA. which is 41.0 Watts of Plate
Dissipation without
any indications of red plates, melting or problems. Whatever its number...
6BQ5, 10BQ5, EL84,
7189, those NOS vintage tubes were quite well made, can't say the same for
any current versions.
Triode offers the 7189/EL84M which works well in the 222C at ca
$50/quad; this is what my
222C uses currently. All the rest (Tesla, Yugo, Russian) are 6BQ5s and
unsuitable.
hth tr --
----------------------------------------------------------------------
Tim Reese, MGH NMR Center
re...@nmr.MGH.harvard.edu
Article:
4 of 9
From:
OvrReactor <ovrre...@aol.com-nospam>
Subject:
Re: Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
28 Sep 1999 17:27:25 GMT
>the plate voltage of the 222C is about 420V with fixed bias
I figured that was the difference in the two Scotts, but I didn't want
to just go shooting off at
the virtual mouth by guessing that the 7189 fitted Scott had a higher
B+ than the 6BQ5
model. I'm a guitar amp guy after all, and we're supposed to be know-
nothing bumpkins.
Best Regards, Tom Mitchell
Article:
5 of 9
From:
Punkerdubh <punk...@newsguy.com>
Subject:
Re: Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
Tue, 28 Sep 1999 13:37:30 -0400
davefr <dav...@REMOVETHISpacifier.com> wrote in message
news:37f01d6a...@news.giganews.com...
I bought a Scott 222C on EBAY. The description said "The output
tubes are strong
vintage Zenith 7189".
[snip]
Hey, I was bidding on that one, but wasn't able to get online when the
auction was closing,
and you (and a few others) outbid me. Congratulations on the purchase,
it looks like a fine
piece. How do you like the sound? Anyways, as others in this thread
have pointed out,
6BQ5's really aren't *supposed* to be used here, but many NOS ones will
work fine. I'd just
get a backup quad of the EL84M (Tesla?) and run the Zeniths until the
conk out.
Enjoy the amp, - Punkerdubh
Article:
6 of 9
From:
<hitu...@my-deja.com>
Subject:
Re: Is EL84/6BQ5 = 7189? (possible misrepresentation)
Date:
Tue, 28 Sep 1999 19:21:09 GMT
David Thatcher
-- Pretty Blue Glow only means the tubes are working properly. Pink Glow or
Yellow Flashes, followed
by internal flames blackening the glass would mean trouble !!!
- SB.
--
Steven L. Bender, Designer of Vintage Audio Equipment
Amp Info Page: http://www.gis.net/~slbender
"I think your analysis is basically correct, and the "white paper" is
excessively stained
with snake-oil and is of little use for anything other than starting fires
intended to
barbecue overzealous marketing departments." -Dave Platt
-**** Posted from RemarQ, http://www.remarq.com/?c ****-
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