8908, M-2057, 6lw6, 6lf6, 8950 sweep tube used in linear amplifiers walkthru
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- Опубликовано: 29 авг 2024
- Picked up the Golden Falcon 1kw amplifier that uses 10 big bad 8908 tubes. I already knew something about 8908 as they are used in the Hygain Footwarmer which I have one now and have worked on in the past. BTW that 2 tube Hygain Footwarmer is one bad bad amp. I thought the 6lw6 was a 6v replacement for the 12v filament 8908's but I was somewhat wrong. After much research, here's what I found:
Almost all common sweep tubes like 6lq6, 6lf6, 6je6c, 8950's and many may other variants are rated at 30 watts dissipation or less. The 'sweep' tube was used in old tube TV sets from the tube TV era. It's purpose was to drive or make the 'sweep' of the dots or pixels across the screen, hence the term 'sweep tube'. During the tube TV days, with millions of tube TV's out there, sweep tubes were cheap and plentiful. When amp makers were designing amps at the time, there were some transmit tubes available, but they were not as cheap and plentiful as TV sweep tubes were. Hence at the time, some Ham amps and most CB amps made took advantage of the price and availability of the TV sweep tubes. Hams may claim to hate sweep tube amps and call them no good now, but if you look at the actual reviews from Hams on the Ham amps that used the same tubes and same design that most CB amps used, the Ham sweep tube amps generally got great reviews, but of course, the CB amps suck..... even though same tube and same design LOL.
So normal sweep tubes are 30 watts dissipation or less, but the biggest and baddest sweep tube made at the time was the 6lw6 tube. It was rated at 40 watts instead of 30 and it was just bigger, fatter, healthier, and more meaty than the common sweep tube. The 8908 is the 12v filament version using the same 8 pin Octal base but be careful, pinout is different. BTW, the 8950 is the 12v filament version of the 6lf6 tube. Since it was available and cheap at the time, some amp makers, like Hygain and Golden Falcon used the big bad 40 watt tubes instead of the more common generics. Later when tube TV's went extinct, GE had many of the 8908's left and Maco who was building multi tube amps using the 12 pin compactron base tubess by the thousands, talked GE into making the 8908's using the 8 pin Octal base into the 12 pin Compactron base and the M "maco" 2057 was born. The insides of the M-2057, 8908, and 6lw6 are identical but the base of the M2057 is 12 pin, and the 8908 and 6lw6 are 8 pin Octal. The M2057 and 8908 are 12v filament and the 6lw6 is 6v filament. The pinout is different on all of them.
6lf6 6v 30 watt 12 pin compactron base
8950 12v 30 watt 12 pin compactron base
6lw6 6v 40 watt 8 pin Octal base
8908 12v 40 watt 8 pin Octal 'different pinout than 6lw6'
M-2057 12v 40 watt 12 pin compactron base same pinout as 6lf6 8950
HI THANK YOU I AM RESTORING A SBE 1 K AMP AND THAT INFORMATION IS VERY HELPFULL TKS KE3XO
Glad it helped.
I figured the 40 watt sweep tubes were used in the biggest 25" color TVs available at the time.
Thanks for the lesson.
I think you are right.
I REMEMBER IN THE LATE 70s AND 80s MY FRIENDS USING MACO 500, 750 AND 1000 BOXES USING THE 2057s AND 8950s . BIG SPLATTER BOXES. I HAD A THUNDERBOLT-305 THAT HAD 6LQ6s. I THINK IT WAS A ONE DRIVING THREE. IT WAS A CLEAN BOX.
Interesting
Odd ending, hope you are okay.
Camera battery died lol
It ended with de feet .🦶🦶👀
Doc tried swapping 6lw6 for 8908 years ago, couldn't get it to work cause on 6lw6 the cathode is tied to g3 internal
and there is another grid that is different too.
@@tramdr The only way to get the 6lw6 to maybe work would be to rewire the tubes grounded cathode and drive the grid like the old galaxy 2000 with the 6hf5 tubes
Hello TramDr, is there a tube that can be used in a falcon 500 beside the 8950?? If u explained and I messed it please excuse, thanks
8950 is twelve volt filament version of the 6lf6 6 volt filament and family of tubes. The only twelve volt filament tube that is a sub is the M-2507 which gives me more power, but is harder to find and costs more than the 8950.
6JS6 'A,B,+C'
6KN6
6LR6
6LZ6
6MB6
6LF6
6LX6
6MH6
6KD6
6LB6
8950 12V Filament
M2057 12V Filament
also note some of these subs have a very slightly Pinout, like some have 2 wires connected to one pin and others may have one connection. Otherwise, they are all subs for each other.
Thank you . What do you suggest I stuff a 10 tube phantom with on the cheap and easy ? Has just about every brand of 6lq6 now 40 to 50% tested makes almost 400w pep now , rough over all condition not original transformers , . 6KM6 ?
6km6 will only do half, maybe use those for drivers. What I would recommend is to use higher filament voltage 6lq6. 21lq6, 31lq6 which can often be found cheap. Also the 6je6 series is a pretty good sub, finding those cheap is hit and miss.
A 6LF6 is 40 watt. The 6LQ6 is 30 watt. 6KD6 is 33 watt. EL519 is 42watt, EL509 are only 30watt. 30MB6 is 38 watt. M2057 is 40 watt. 8950 is only 33 watt. 6LX6 is only 33 watts. Many people believe the 6LX6 are 40 watts like the 6LF6,but GE clearly lists them as 33 watts. Just some info over my years of repairing and building. Been working with sweep tubes for 50 years. I know them all pretty well. I have data sheets on most. Actually the 6LW6 is a hard data sheet to get. It is 40 watts. I have been using the EL509S by JJ. It’s an octal base sweep tube,42watt but has no plate cap. The plate is on a pin on the base. They work very well though. I made a JB200 knock off with 2-EL509S, that will do about 480 watts. Even better then a JB400 with 4-6550’s. You need a heavier duty power supply, but they work. Anyway. Cool video. We should talk TramDr. 73.
I've seen a 6lf6 rated like that but no, it is not.
What average level of 120ac amps do these draw on tx? 15amp, 10amp or less?
Fourteen amps at full output
@@tramdr Nice. Tubes seem THE way to go. Sorry 80 amp 15v dc power supply, and the wattage seems like seasoning swing with solid state. Tubes seem to enjoy making a concrete slab of a carrier, without relying on overdriven audio to pump the swing. 73's and click-click.
Are these all compactron 12 pins?
Nope
You didn't say anything about the 8950
8950 is a 12v filament version of the 6lf6 with slightly improved specs for the upper end of HF and lower end of VHF. Many people look at the slightly improved specs and say its a more powerful tube, made for RF blah blah blah. However, those improved specs are good for the higher frequencies, like 50mhz and above, but they don't really do anything for the 10/11 meter band users. Also, I have said this many times, I always use the Plate Dissipation to determine the output of a tube. With the 6lf6, 8950, 6kd6, 6kn6, 6lx6 and a few others, they use the same Plate which means they have the same plate dissipation. One problem is how different people rate their stuff. Think about a stock SSB CB. It does 4 watts AM and I2 watts SSB. A manufacturer could rightfully call it a 4 watt or I2 watt by measuring it different. It's the same with tubes. The same tube maybe 30 watt plate dissipation used as a TV sweep tube, that may be on for hours or days at a time, continuous duty. But used in a CB or Ham amplifier, which normally won't be on more than about 33% of the time in a given hour, you can uprate that plate dissipation using the Ham ICAS standard. If it is class B or C, it can do even more. As someone else said, but he was talking about the 8950 only, it can be temporarily overloaded to about 3x the plate dissipation. Yep, all sweep tubes can do that since they were originally rated for continuous duty, the rating can be 3x higher when used for temporary RF. Its kinda sad though that people keep arguing and throwing specs to me about this one. The plate on those smaller tubes in my vid are 30 watt continuous, period. The plate on the larger tubes are 40 watt continuous period. Problem is when you start comparing apples to oranges. On the net, I saw the 2 biggest named Hams arguing with each other about how many watts coax can handle. Stupid argument. Same problem. Continuous duty, vs ICAS, vs CW vs AM vs SSB and also whats the point that you find the coax is at its max? When it fails? When it loses 2% of its power in heat? 5%? I0%? No right answer, but with tubes, I just use continuous plate so I can compare apples to apples.