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 Post subject: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 11:27 am 
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Location: Phila Pa
The set I am working on is a 10 tube Zenith from 1937....10-S-153
It calls for a pair of 6F6 output tubes, But it is running a set of nice ST 6L6s which look pretty good in there, BUT I am wondering since I havent been finding much info on these different tubes,
Which draws the least current so I can be kind to the transformer?
Which sounds best? Not that I could hear the difference and which do you prefer and why?
There are so many subs for this tube it surprises me...... Too many options.
OK, I will check back, Off to that Job thing.
Peter


Last edited by pred on Dec Sun 11, 2011 5:22 pm, edited 1 time in total.

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 1:27 pm 
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Those tubes are somewhat similar-- the series started off with the 6F6 which may be a rebased 42-- it's a pentode. Then RCA stole or bought the rights to the "beam power" design and made the 6K6, which is okay, the screen current is lower anyway. Then they souped it up a little and called it the 6V6, then souped it up a lot more and made it the 6L6 and not long afterward rebased it as the 807, then later with the plate scooted out a bit and the beam plates scooted in, as dozens of very slightly different TV sweep tubes. The plate had to go out to handle the retrace voltage peaks and the beam plates scooted in so the tube could "bottom" better.

Quite often, like almost always, the audio tubes are used with cathode or B- bias, so the bias adjusts itself to a reasonably safe level no matter which one of these tubes you plug in. Some of us have been known to replace 6K6's and 6F6's with 6V6's, just because the 6V6's are more common and one might get a smidgen more volume and power out.

But for best authenticity, you should strongly consider starting to look for the original tubes.


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 2:10 pm 
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There is not a lot of difference in the bias requirements at 250V between the 6F6 and 6L6 and it is not uncommon to see a 6L6 in a 6V6 hole. The latter is more likely to cause issues as the 6V6 uses less grid bias.

6L6 is a beam tetrode, technically a "renode" as it has no actual grid structure. It is normally used with a much lower plate load (2500 vs 7000 for 6F6) as it has greater plate dissapation and will in that configuraton put out nearly twice the output of a 6F6.

I would also consider it better to put the set back too original.

Marc


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 2:44 pm 
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Joined: Oct Mon 02, 2006 5:18 pm
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Location: Central Michigan
pred wrote:
The set I am working on is a 10 tube Zenith from 1937....10-S-153
It calls for a air of 6F6 output tubes, But it is running a set of nice ST 6L6s which look pretty good in there, BUT I am wondering since I havent been finding much info on these different tubes,
Which draws the least current so I can be kind to the transformer?
Which sounds best? Not that I could hear the difference and which do you prefer and why?
There are so many subs for this tube it surprises me...... Too many options.
OK, I will check back, Off to that Job thing.
Peter


Peter, the schematic actually calls for 6L6/6L6G's. I have a 10S155 which uses the same 1004 chassis and IIRC the tube sockets are actually marked 6L6/6F6, so Zenith says you can run either tube. The 6L6 has a heater current of .9 amps and the 6F6 has a heater current of .7 amps.

BTW, note that the schematic specs the line voltage at 112 volts for this chassis.

http://www.nostalgiaair.org/Resources/682/M0024682.htm

Another interesting fact about this chassis is that it is one of the few Zenith chassis which were spec'd to use either glass or metal tubes.

Have fun with your radio.

Ed

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 6:12 pm 
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Ancient_Hacker wrote:
Those tubes are somewhat similar-- the series started off with the 6F6 which may be a rebased 42-- it's a pentode.


No maybe about it, 6F6 is an octal 42.

Quote:
Then RCA stole or bought the rights to the "beam power" design


one or the other . . .

Quote:
and made the 6K6


BZZT. As the 6F6 is to the 42, the 6K6 is to the 41. 6K6 is a rebased fat-pin pentode, it is not a beam tube.

Quote:
Then they souped it up a little and called it the 6V6, then souped it up a lot more and made it the 6L6


Souped...?

The 6L6 preceded the 6V6. The 6L6 was the first beam power tube, meaning the it's suppressor grid was substituted with an element that formed a concentrated electron beam

Quote:
and not long afterward rebased it as the 807


true

Quote:
then later with the plate scooted out a bit and the beam plates scooted in, as dozens of very slightly different TV sweep tubes.


There were a number of sweep tubes with and without plate caps that were internally identical to the 6L6/807: 6AH6, 6AL6 and 6BG6 all have 6L6 ratings.

Quote:
The plate had to go out to handle the retrace voltage peaks and the beam plates scooted in so the tube could "bottom" better.


Um...[in unison] Yes, Mr. Garrison. :lol:

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 9:22 pm 
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That's how we keep history fresh-- by slightly rearranging the timelines.

You are of course correct, the 6L6 was introduced about a year before the 6V6.


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Fri 05, 2011 10:24 pm 
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Quote:
stole or bought
I believe the term you're searching for is "cross-licensed," from their British affiliate. Sorry I don't recall off the top of my head who the patentee was. They chose not to develop the beam-power principle, but RCA did.


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 2:22 pm 
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Now that the missinformation has been straightened out lets get back to the original question.

The easiest way to keep the transformer happy is to use 6V6's as the filament and plate current draw will be less while providing very close performance. The only caveat is to be sure the 6V6 plate and screen voltages are within spec as some manufacturers ran the 6F6 right at the 375V edge.

Carl


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 3:30 pm 
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Location: Phila Pa
OK, I will try and dig up some ST 6V6s for this set,
These old Zeniths seem to need lower voltages to keep the transformer happy and at 112 V like the schematic says the transformer sits at 120* after a couple hours of use in a 78* house.
I would think that with a set of 6V6s in place of the 6L6s the trans temp may drop a degree or few.
Peter


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 6:32 pm 
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Posts: 3010
Location: Boston, MA USA
pred wrote:
OK, I will try and dig up some ST 6V6s for this set,
These old Zeniths seem to need lower voltages to keep the transformer happy and at 112 V like the schematic says the transformer sits at 120* after a couple hours of use in a 78* house.
I would think that with a set of 6V6s in place of the 6L6s the trans temp may drop a degree or few.
Peter

Please use the correct tubes for the set. Please do not use a 6V6 in a circuit designed for a 6L6. The ratings of the 6L6 far exceed those of the 6V6. In this set the plate voltage (320V) exceeds the spec for the 6V6 (315V design-center).

You can download the data sheets for the 6L6 and 6V6 and compare for yourself, if you like.

This set was designed for the 6L6 for a reason. If the designers had intended the set to use lower-rated tubes they would have specified them.

-David


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 6:53 pm 
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different tubes different specs different applications http://tdsl.duncanamps.com/tubesearch.php
gotta have some flexibility :shock:

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 7:09 pm 
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tubeAMP wrote:
different tubes different specs different applications http://tdsl.duncanamps.com/tubesearch.php
gotta have some flexibility :shock:

No, as long as you are lucky enough to be able to get the right tubes, use them. Don't EVER run tubes above their ratings. No flexibility on that.
tubeAMP wrote:
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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 8:48 pm 
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flexibility is manufacturing different tubes for different applications. use the right one :shock:

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 9:42 pm 
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Well, good to see that this isn't a debate over which one sounds the best!
Of course, we all know which one that is.. :lol:

- It's the one that's right for the application! 8)

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sat 06, 2011 11:45 pm 
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Simple, if you're dealing with the big black dial Zeniths from 1936 to 1938:

1936: 6F6G
1937: 6L6G
1938: 6V6G

Bob


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sun 07, 2011 12:43 am 
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I am that I am :shock:

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sun 07, 2011 1:01 am 
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I meant 6AH5(G) above not 6AH6, sorry. Dang typos.


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sun 07, 2011 1:30 am 
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dberman51 wrote:
.......The ratings of the 6L6 far exceed those of the 6V6. In this set the plate voltage (320V) exceeds the spec for the 6V6 (315V design-center)......


-David


I wonder why Fender engineers never paid any attention to this?I worked on a 1964 Princeton guitar amp a while back and the two 6V6s were being fed 420 volts to the plates,just a stated in the service literature..The tubes were original to the amp and didn't seem to mind the excessive voltage.


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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sun 07, 2011 1:35 am 
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dberman51 wrote:

This set was designed for the 6L6 for a reason. If the designers had intended the set to use lower-rated tubes they would have specified them.

-David


Apparently David you missed a post back up a few. This chassis came in Several different cabinets. Some console cabinets with 12 inch speakers and one in a large tombstone with only an 8 inch speaker.

If you look at the Tube Sockets it says on them 6L6 / 6F6 notice no G on the tubes so yes Zenith on this chassis said you could actually use metal tubes in it. Strange as that may seem. And of course if you look at the tube books the 320 volts is a bit over for the 6F6 even though some companies were known to run them that high. Its also 1937 the year before the 6V6 G tube came about.

So Zenith themselves said its OK to run 6F6 tubes in this chassis. Since at the time the chassis was built the 6V6 didn't exist yet guess I don't see the problem with using them rather than really overtaxing the 6F6 tube.

"Quote from Mike C.. "I wonder why Fender engineers never paid any attention to this?I worked on a 1964 Princeton guitar amp a while back and the two 6V6s were being fed 420 volts to the plates"

Same reason as Zenith feeding 320 Volts to the plates on a pair of 6F6 tubes!

John k9uwa

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 Post subject: Re: 6V6,6L6,6K6 and 6F6, WHat's the diff?
PostPosted: Aug Sun 07, 2011 3:14 am 
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I looked at the schematic from Nostalgiaair and it indicates 6L6. It didn't indicate, or I didn't notice, any alternatative tube types for the power stage.

Regardless of what Fender might have done, I do not recommend exceeding rated plate voltage on any tube. Flashover can destroy not only the tube but also an output transformer instantly.

The original 6L6 and 6V6 types were metal. Not sure when the glass versions were introduced. For many years they were sold alongside each other and you had your choice of glass or metal.

-David


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