8908 / 6lw6 / M2057 Biggest Baddest Linear Amplifier Sweep Tube made explained Hygain Footwarmer Amp
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- čas přidán 10. 09. 2024
- I got 2 Hygain Footwarmer's that use 2 8908 tubes each. I also have 2 Golden Falcon 1000's that use 10 each 8908 tubes. Hence, I could use a ton of good 8908 tubes. Problem is 8908's are the hardest to find and the most expensive sweep tube made. They are almost unobtainium, but RF Parts does sell them for $100 a pop. I'm not ready to spend that kind of money so I did my homework and research:
Both the 8908 and the 6LW6 tube where the biggest and baddest and the last of the Television sweep tubes. They were called 'Sweep' tubes as in the old tube type TV's, the sweep tube controlled the dots or pixels sweep across the screen. As TV's got bigger, the sweep tube needed to be more powerful and hence the big bad 8908 and 6LW6 tube was born. Problem is at around the same time, the transistor was replacing all the tubes in a Television except for the CRT. Hence, the TV market for vacuum tubes was dying and GE had a bunch of newly fangled 8908 big bad sweep tubes. At the time, the CB market was booming and like it or not, so were illegal CB amps, with most of them using common and cheap, at that time, TV sweep tubes. Golden Falcon and Hygain were a couple of amp makers who used the available 8908 tubes. One of the biggest CB amp makers, like it or not, at the time was MACO. Maco got with GE which had a lot of now pretty much obsolete 8908 tubes and got GE to put the 8 pin Octal 8908 into a different base and pinout, the 12 pin compactron type base which was the same base and pinout of the popular 6lf6 and family tubes. So, with the 8908 in a 12-pin base, the M-2057 tube was born. The M-2057 did have a 12v filament and other than being bigger and capable of more power, was almost a drop in replacement for the 12v 8950 tube and with a filament change, was a replacement for the 6lf6 and family tubes.
Back to the 8908's and replacements and subs. The only big bad 40 watt sweep tubes made were the 6lw6, the 8908, and the M-2057. Same tube, but totally different base for the M-2057 and different pinout and wiring between the 6lw6 and the 8908. Hence, there is no drop in replacement for the 8908, but if you address the pinout differences, a 6lw6 is the only viable replacement. However, there is a catch. Since the 6lw6 has the suppressor grid, grid 3 tied internally to the cathode, the 6lw6 cannot be used in a grounded grid amplifier (which most CB amps are). With a grounded grid amp, the grids are.......grounded LOL. The drive in a grounded grid amp goes to the Cathode. However, since the 6lw6 has the suppresor grid tied to the cathode, driving the cathode won't work as that would also mean the suppresor grid would get drive and that's bad news. Hence, a 6lw6 can only be used as a grid driven amplifier.
So the good news is in amps that are grid driven, like the Hygain Footwarmer, a 6lw6 can be made to work. The bad news is in most other amps, like the Golden Falcon, a 6lw6 won't work at all without heavy modding. Now that I have the pinout, I will be looking for 8908's drop in replacements, but as I said earlier, they only made 3 40 watt sweep tubes, so if I find one, it won't be a big bad 40 watter.
Much Appreciated.
Foot Warmer, intel.
Love mine. GREAT Driver
Tubes...it's what's for Dinner!!
The Russian sweep tubes are the cheapest (like $15) and the most rugged, but they require a socket change. I was doing that 25 years ago when I was doing that kind of work.
thats why i dont work on sweeper amps . 572b or better amp is all ill work on getting parts is getting ridiculous. el509s /6kg6 i thought would have held on a little wile longer but they didnt 2057 is a decent tube but you need 4 of them to hang with a cheap ceramic tetrode ... i just found in a high volume repair shop sweepers are not worth my time unless someone is willing to put $3-500 into a boat anchor .... time is money folks down river from you dont spend much as you surely already knew .. one day i need to come up and meet you we have a few mutual friends ..
ive pritty much left the cb repair hobby and put my time into amateur radio and solid state vintage audio repairs at this time .
Rocker switch
0:49 Rocker switches. 😉
Thanks, Senior moment! Sometimes I feel like Joe Biden, Mic in one hand, cam in the other hand, then stumbling with words in the middle of the video.
@@tramdrI know the feeling. 😂
Those are rocker switches.
I came here to say exactly the same thing lol