amplifiers

[accoolman]

{Cry_river}how many watts dose it take to drive my varmint xl-750 and many is to much

 

[RadioGuy772]

This is an older "sweep tube" amplifier, as you may or not be aware, the tubes in this amplifier were never meant to be used as an RF amplifier. The reason they were used back then, is that they were plentiful and cheap, and did work to amplify RF, but their original application was for use in older tube type TV sets as the horizontal output tube. That's why the slang term given was "sweep tube" because they were used in the horizontal sweep section of the TV set.

Because they are no longer made, and weren't very rugged to begin with, care should be taken to not over drive them. Things get even worse when you try to push them into AM service. For SSB they would work OK, but when you have a lot of CB guys using them on AM, for something they were never designed to do, and then take a step more, and they try to get every last watt out of them......use your imagination as to how well they work and for how long.

So to sum up, I would keep the carrier level low, about 2 watts, and peak at 8-10 watts max. On SSB, I would say 12 watts PEP. If you do this, the amplifier will last a while, providing the capacitors are still good. Those are the only other part that would really wear out on these amplifier due to heat and age.

 

[accoolman]

can these tubes be replace with a new type thank you

 

[North Texas Mudduck]

1 to 2 watts deadkey with 12 to 15 pep
might look into the 8950s
have seen a varmint 1000 converted with the 8950s

 

[RadioGuy772]

Why ON EARTH suggest 8950s? They are another sweep tube even MORE scarce than some of the others. They are the 12 volt filament version of the 6LF6, essentially. Go to a uncommon tube that is more available. When I say "uncommon" I mean, not commonly used up in CB amplifiers because the most common replacements that were direct swap outs were the 12 volt versions, and the 6 volt versions. Most of the guys running these amps are totally unaware that a 6LF6 for instance can be switched out for a 24LF6, 24LB6, 30LF6, 35LR6, etc. All you do is change the filament voltage either by using an outboard power supply of the correct voltage, OR if you have the right tubes, and the right amount in the amp, you can wire them in series. Example, if you wanted to use 6 tubes you would use 6 total 20LF6s for a total of 120 volts on them, and you wouldn't even need a transformer, just wire them with a fuse across the 120 volt AC supply from the wall. Same applies to other voltages / combinations of tubes. The ones that have oddball filament voltages are more readily available and less expensive than the direct swap outs.

 

[Shockwave]

There are dozens of tubes directly interchangeable with the 6LF6 in linear applications. Many are obscure and not typically used. My secrete is buying something like 6KN6 on eBay. It's like before everyone figured out to use 6LB6. Now 6LB6 is expensive too but 6KN6 is often $25 for NOS and has a 6 volt filament.

 

[accoolman]

thanks for the help