LA2A ECC99???

[ilfungo]

Can I use ECC99 in place of 12BH7 in LA2A?
I have to make modifications to the circuit?
Thanks

 

[[silent:arts]]

You can.
At least I do.
Without modifications.

 

[CJ]

i am using a 12SN7, no mods, sounds great, cheaper also,

6913 also works but nobody has those in the tube caddy,

CV5042 should also work,

12BH7 is based on the 6SN7, octal socket is easy to wire compared to 9 pin,

http://www.groupdiy.com/index.php?topic=50096.msg633910#msg633910

600:600 for input only works for hot signals,

 

[ruffrecords]

12BH7 is based on the 6SN7, octal socket is easy to wire compared to 9 pin,

The 6CG7/6FQ7 is the B9A equivalent of the 6SN7 with characteristics near indistinguishable  from its namesake.

The 12BH7 is a different beast altogether, lower mu and plate resistance and inferior distortion characteristics.

Having said that, in this application there's no reason why it should not perform admirably.

Cheers

Ian

 

[CJ]

from Tube Lore  by Ludwell Sibley,

now there's a bar room name for ya,

 

[ruffrecords]

from Tube Lore  by Ludwell Sibley,

now there's a bar room name for ya,

Just does to show you cannot believe everything you read on the net.

I have emailed him to ask for the source of this info.

Cheers

Ian

 

[CJ]

well, he could be wrong too,

most of the stuff i post is wrong, that's why you see "modified 6,754 times" next to all my posts, 

 

[ruffrecords]

well, he could be wrong too,

most of the stuff i post is wrong, that's why you see "modified 6,754 times" next to all my posts, 

Can you check out what the book says about the 6CG7 and 6FQ7 because my own tests have shown they are almost indistinguishable from a 6SN7.

Cheers

Ian

 

[CJ]

i did already and Mr. Ludwell has somehow forgotten to include these in his cool book,

he lives in Ashland Oregon now, maybe i should go have a word with him

tubes are more forgiving than transistors as far as substitution, all you have to do is look in the tube catalog, match up the plate resistance, plate current, bias voltage  and amplification factor and you can try out different tubes for substitution,

i do have this from a book of equivalents, now this book is really questionable so your mileage might vary with this one,

group 244>

 

[ruffrecords]

Here's what the man himself said in reply to my email:

Well, I can't recall my state of mind in 1996 while writing up this type,
but it was pretty clear that it had pointed toward the large and expanding
market for the ()SN7GT - "every" North American TV set used three ( )SN7s at
the time.  In many (most?) cases it was a functional equivalent, hence I
don't think "based on" is too much of a stretch.  Other types were closer
equivalents of the ( )SN7, but the differences found in the 12BH7 weren't
necessarily a bad thing.

Now that more is known, here's how Hytron promoted its tube (they developed
and registered it) in their 1951 news release E-149A:

"The increase in perveance over types like the 6SN7GT or 12AU7 is such as to
make one section of the 12BH7 suitable for use as a vertical deflection
amplifier in television receivers using wide deflection angles.  The tube is
designed to withstand relatively-high peak positive plate potentials, and
accordingly is specifically rated for use in the vertical deflection socket
as well as being rated for the usual Class A applications." {The peak rating
was 1350 V.]

RCA didn't have to be so charitable in-house.  Here's how their internal
product-management record (TCA Data Cache DVD-ROM) put it:

"The A-4616 (12BH7) is a 9-pin miniature equivalent of the 6SN7GT but with
transconductance increased by use of a formed grid.  The increase in
transconductance is desirable for vertical deflection service where
performance of the 6SN7GT is marginal in certain applications.  . . .
Published ratings are higher for voltages and as the 12BH7 becomes
available, it is expected that new receiver designs will use this type to
replace the 6SN7GT."

This looks like a classic product-improvement case, so I don't think "based
on" is a wild claim.

Ludwell Sibley

Fascinating stuff. This guy really has the inside track on how tubes developed. Seems to me to be a generally updated version of the 12SN7 intended for use with bigger TV screens. I guess it means we are both right!!

I have asked about the omission of the 6CG7/6FQ7 from 'Tube Lore'. I'll let you know what he says.

Cheers

Ian

 

[CJ]

wow!  gerat work Ian!  and full props going out to Sidney too!
Tube Lore is a great book, he even has CRT's from TV sets in there, and a lot of other weird tubes,

 

[ruffrecords]

wow!  grat work Ian!  and a pretty rapid response considering...

Tube Lore is a great book, he even has CRT's from TV sets in there, and a lot of other weird tubes,

I would love to get a copy but they seem as rare as hen's teeth right now. The cheapest I have found on this side of the pond is over 1000GBP!!!!


Cheers

Ian

 

[CJ]

he has EMIAC's in there also,

there might have been a supplement with the 6CG7 in there, a few pages that probably fell out of the back,  ???

review>

"What do you do with your leg immobilized in a cast for the better part of a year? If you're Lud Sibley you produce the "ultimate" tube resource book -- Tube Lore.

There are already histories, tube manuals, substitution guides, and collectors' reference books, new and old. This book complements all of them. You won't find in it a history of the Audion, but there is an amazing amount of material on later tubes. You won't find the level of detail found in a tube manual, but there are major specs for almost every tube ever made in the U. S. (some post-1950 TV types excepted). You won't find an oversimplified list of substitutions, but there are cross-references to all variants, including 4-digit types with upgraded characteristics. You won't find the concentration on one subject as in Tyne's Saga of the Vacuum Tube or Stokes' 70 Years of Radio Tubes and Valves, but a collector will have this book dogeared in a week.

What more will you find? The list goes on and on: Manufacturers' date codes; EIA registration (introduction) dates; model numbers of military gear and broadcast transmitters that use certain tubes; comparative specs for sweep tubes, and lists of ham gear and audio amplifiers that use each type; compiled auction prices for collectible tubes; rejuvenation data; tube testing; manufacturer code numbers (who really made those tubes?); explanations of the numbering systems; trivia and not-so-trivia galore. It's all here, over and above the play-by-play on the tubes themselves.

I was slightly disappointed to find nothing on several vertical-output tubes that have audio applications: 6BL7, 6BX7, 6EA7, 6CK4; the 6CK4 was even promoted by Sylvania for audio use. Granted this data is all in standard tube manuals, but the EIA registration dates might have been instructive, since other "worthless" TV types made the roster.

There are a few mistakes and typos, but considering the sheer quantity of information, the error rate must be down around 0.0001 percent.

Lud and I have an ongoing discussion about indexing and organization. Editors like to categorize (all the RCA 2000-series in one section; all the EIA 5500-series listed in order, etc.), while users would be better served by a single alphanumerical listing, so they wouldn't have to decipher the author's classification scheme before looking up a tube each time.

The historian or browser who wants an overview of, say, the RCA 800-series transmitting tubes will appreciate the chosen format. The guy who finds an S856 in a box of tubes and wonders what it is (an 0-A2) will have to search for it in the "general" section, while an SB846 appears in the "Sylvania developmental" section.

Yes, there is an index, but it says all "800" tubes are in the RCA listing, and does not show any "S" prefixes. Looking up an S856 would require knowing beforehand that it is "nonregistered" (the chapter heading "general" does not appear in the index). This indexing dilemma may be insoluble, but the reviewer's job is to point these things out.

Do you really need the specs on an 8568 (20-megawatt klystron used in the Stanford Linear Accelerator)? Maybe not, but if you were given a pair of 8122s, it might be useful to know that they fit a National NCL-2000 linear. Do you need to know the manufacturing date of a tube? Yes, if you wonder if a radio still has any of its original tubes. Can't recall where you saw that article on rejuvenation voltages or times? No matter, it's all here in one place. Wish Tyne and Stokes in their books on tubes hadn't stopped in 1930 and 1940 respectively? Right up to Nuvistors and Compactrons, there's a lot of later tube lore in Tube Lore."