Sweep tubes, 6lf6, 8950 30 watt and 6lw6, 8908, and M2057 40 watt tubes compared.
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- Опубликовано: 13 сен 2024
- There is still a lot of misinformation out there on linear amplifier sweep tubes. Even some tube data listed on the net is wrong. Here is a comparison of common 12 pin sweep tubes used in amps like Maco and Palomar vs the hard to find 40 watt tubes the 6lw6, 8908, and M-2057.
Back in the day, before transistors and IC's, TV's used tubes for all their circuitry. The screen was a huge Tube. A 9" TV had a 9" tube for the screen. A 25" TV had a 25" tube for the screen. One part of the tube TV circuit was a device to make the TV screen Dots go from dot to dot or sweep across. Since the device used was a tube to make the 'sweep', that tube was called a sweep tube. TV sweep tubes came in many different variations and power levels to perform that function. Some where as low as 10 watt and the biggest made was 40 watt. Back during the TV tube days, TV sweep tubes were plentiful and cheap. TV repairmen had Tube cases and kits with all manner of tubes in them. BTW, my Dad was one. During the 60's with sweep tubes being available and cheap, some amp manufacturer's used them in mostly the small and medium size amps. Funny to me that these Ham sweep tube amps generally got good reviews from the Hams, but the later CB sweep tube amps using the same tubes and designs was much maligned. Most of the sweep tubes used in amps are the larger 30 watt tubes. Nowadays, 40 years after the last sweep tubes were made, the available, common and cheap sweep tubes from back then are not as available, not so common and certainly not cheap. Hence, people are always looking for a cheaper substitute of replacement. Nowdays they still make audio tubes and some are bigger and more powerful than the old 30 watt sweep tubes. However, audio tubes can work up to 30mhz but are not ideal for RF. Also, the base, pinout, and plate cap is different. There are sweep tubes with lower power levels that are available and rather cheap. Reason being, who wants to retube an amp with these lower power tubes and then get 1/2 power out of it?
The big bad 40 watt sweep tubes developed from the big bad 6lw6 40 watt sweep tube. It was used in the larger tube TV sets before transistors took over. The 6lw6 uses an 8 pin Octal type base. I know of no amps that use the 6lw6 but there is the 12v filament version with the same Octal base, the 8908 was used in a few amps. The Hygain Footwarmer and some Golden Falcon amps and a few more. The 8908 used the same base, but not only was the pinout slightly different, on the 6lw6, grid 3 is internally connected to the cathode. This make the 6lw6 impossible to use for grounded grid amplifier operation, but it can be used in grid driven amps, like the Hygain. Last of the 40 watt tubes was the M-2057 tube. This came out at the end of the tube TV era and during the height of the CB boom era. Maco was pumping amps out by the hundred's and with each amp using multiple's of tubes, they were using thousands of tubes. Maco ended up talking GE into taking the 8908 tubes leftover from the TV era and putting them into the 12 pin compactron base that Maco and others were using and hence the M-2057 tube was born.
In conclusion, the only true 40 watt sweep tubes....not transmitting tubes, not audio tubes, etc..... made were the 6lw6, 8908, and M-2057.
Back in the day I remember some of the old timers saying this.
Thank you for the refresher course.
Thanks.
A pair of 6JB6s were used as the final output RF amplifier in Drake ham radio transmitters. While the Drake transmitters were rated at 200 watts input and they actually did that, they used very carefully controlled transmitter mode. In particular, the AM mode was "modulation controlled carrier." So, high power only occurred during spoken syllables, but power was reduced during quieter times. The power meter bounced around a lot during transmission. As I recall, the tubes were only rated for 65 watts for the pair, but they tripped the effective usability by implementing very efficient modes.
Yep, so many different variables and rating for sweep tubes. Plate dissipation, class, ICAS, Power in, power out, and temporary overload ratings. It is said by the sweep tube guru's that the plate dissipation rating can be x3 when used for AM and SSB ICAS amplifier's.
I have stack full of all of them thank goodness😊
which one's?
Bunch of 6 lq6 and a few m2057 a few 8950
Thats some good cheddar.
The two 8950's were both made by GE as evidenced by the sandblasting in glass
didn't know that, thanks.
Common sense says the larger tubes handle more power; the pins handle more current. Sometimes, you're better off talking to a wall 😂
Agreed.
Plus the 6mj6 utilizes a Kover infused plate cap which should help with heat and power transfer..
Yes but good luck finding those.
Check your datasheet on 6lf6.I did and it is 40W plate dissipation.All the tube manuals I have check it as 40W.Keep on keepin on Doc 73
I've probably looked at around 50 data sheets. Most say 30, some say 33 and a few say 40. Here's a discussion on the net about 8950's and 6lf6. I find these discussions and opinions very interesting. antiqueradios.com/forums/viewtopic.php?t=175524
Excellent information as always Ron,sadly for every piece of verified,sound information we put out there are 50 more pieces of just flat out bad/wrong information being touted as “Fact”. When you have an upload it’s always a good day around the 727 stack 😂 Anyways Kid,I hope you and the 44 are having a good weekend my old friend. 727 Maryland waving I’ll see ya 🤙
How about the 6mj6, much larger compared to the 6lq6\6je6c??
original 6mj6 are like an HD version of the 6lq6, problem is, you pay for what you get.
Good stuff right on target
Thanks 👍
The data sheets are on franks electron Tube Data sheets the 6lf6 is 40w and the 20lf6 is 40w but the 20lf6 has a 200w overload rating for 40 seconds. I'd say these would be the tall boys with the big heat deflectors on top. the data sheets are legit. I been up and down with 20lf6 cause I had a kenrich 515. those tubes were made in Holland and or England for GE and had a folded seam on the top glass and a silver strip on the bottom. they were super duty
Pope, Valvo, Adzam, Amperex, Mullard, Miniwatt Dario, and Radiotechnique were all names owned by Philips Holland.The respective names typically referred to factories. For instance, Mullard operated in England, Valvo in Germany, Amperex in the U.S.A., and Radiotechnique in France. In the case of Adzam and Pope, these were names to export Philips products into other markets such as Latin America and Africa.
Where do the 6LQ6 fall?
28 watts vs 30 watts for 6lf6 so right under.
Bro... I need that hygain 8908 for my footlocker. Is it available?
Nope, no extra 8908's. However, the Hygain footlocker is grid driven. A 6lw6 should work but you will need to rewire the pinout, and 6lw6's are 6v filament while the 8908's are 12v so that will need to be addressed too.
Pretty sure 8908 is 6.3v
I have a amp with 6lq 6s can I run 89.50 instead
No
@@tramdr thank you
Sing your song tramdr!
but I can't sing or dance LOL.
How can I get in contact with you tram dr ?
Tramdr at Yahoo.com