Six pill High Drive Fat Boy

[QROdx]

+1
I'll give you that because I admit that I get things twisted in my head at times.
having sat here and reread this thread and thought about it for a while I saw that I had reversed my own logic.....

I was wrong twice, once about thermal increase causing class changes more toward C and also about diodes in the texas star bias.

heat will make the amp go more toward AB it is added voltage and added drive that will go more toward class C

and the only diodes in bias are on the biggest texas stars, the rest use resistors.
I could have accidentally typed diode instead of resistors but still it was a mistake.

 

[byron81ward]

Well i should be ok driving it with 140anything watts then? I have the 200 amp fat boy power supply witth it

 

[ExitThirteen]

I wouldn't hit it with anything more than 140. About 100W would be best. Are you using this AM or SSB?




~Cheers~

 

[BOOTY MONSTER]

+1
I'll give you that because I admit that I get things twisted in my head at times. ............. I was wrong .............

been there and done that more than a few times . crow taste better when you season it with humbleness and knowing better next time










i always find it fascinating that folks will spend so much money on a amp having no idea how to use it or what it is capable of .......................







.

 

[Robb]

I don't think that the TS amps are necessarily wrong in their amp design/biasing. In and of themselves, they work in AB mode so long as the end user adheres to their recommendations for input power:

Texas Star Export Feature Chart

Of course Joe Blow CB radio operator doesn't bother to check that out.
They listen to their friends advice - and their friends' friends.

So; is TS wrong in their in designing their amps as they do? Or is the end user responsible for the results? IMO - they should have added a regulated supply for biasing. I agree. But not necessarily needed if operated within guidelines. This should also apply to the voltage that the amp is fed with as well. The spec sheets for these transistors are clear on what voltage they require ('12.5v') for the best linear operation. But how many CB operators bother to do that? Voltage increase - as well as too much RF input power - will also make the transistors run hotter and cause the tracking diodes to lose control of AB biasing. One can do whatever they want with these devices; but just don't call any amp a 'linear' unless one has done everything possible to meet the datasheet requirements - IMO.

As far as how much power a 2x4 FatBoy amp needs for the input in AM mode and C class biasing; the answer is 'as high as it can go before it fries the transistors' or 'whenever you get tired of replacing transistors and wasting money on amps'. Whatever FatBoy tells you to do, you will end up doing anyway . . .

http://www.worldwidedx.com/amplifiers/93982-quick-dirty-class-ab-mod-kl300p-3.html

 

[The Mad Scientist]

Hi all ,I would like to add something about the Texas Stars. there are problems with the bias devider network in their mid size amplifiers. the 25 ohm sandbar resistors go high in resistance over time and reduce the bias voltage, and also there are problems with the 10uh chokes that they were using. They also go high in resistance thus reducing the bias voltage even further.

The chokes have been changed in the recient designs with a thicker copper wire on the coil forms and seem to do a little better.

I would have to agree that a regulated bias supply would be a much better design for use in these amplifiers like the one that was posted earlier. And an acitve bias tracking would be even better. But operating the amplifier within reason and cooling it properly should help with the posibilty of thermal runaway.

 

[byron81ward]

am mostly but i do talk side band but only keyed it a couple times getting around 1000

 

[wavrider]

am mostly but i do talk side band but only keyed it a couple times getting around 1000

It seems that you enjoy watching the meter swing instead of making sure you are transmitting a clean signal.

Do your fellow operators a big favor and invest in a dummy load, the kind you connect a coax to, not the kind that keys a microphone.

Enjoy watching the "swing in your thing" until you destroy the amplifier.

 

[byron81ward]

Well ive made several contacts on side band now was told by everyone ive talked too not to change anything was told 181u southern il. Sounds great made contact yesterday with south austrailia and talked for over 20 minutes

 

[9C1Driver]

Hi all ,I would like to add something about the Texas Stars. there are problems with the bias devider network in their mid size amplifiers. the 25 ohm sandbar resistors go high in resistance over time and reduce the bias voltage, and also there are problems with the 10uh chokes that they were using. They also go high in resistance thus reducing the bias voltage even further.

The chokes have been changed in the recient designs with a thicker copper wire on the coil forms and seem to do a little better.

I would have to agree that a regulated bias supply would be a much better design for use in these amplifiers like the one that was posted earlier. And an acitve bias tracking would be even better. But operating the amplifier within reason and cooling it properly should help with the posibilty of thermal runaway.

I sure wish Joker amplifiers were still being made. Peakaboo's regulated AB bias scheme was superb, and the build quality was second to none.

 

[Wire Dawg]

Academics & ethics get in the way of an answer. Seasoned hams & technicians that have witnessed the advances of electronics and cherish the science behind a clean signal quickly recognize the compromises that radio equipment manufacturers make for $$$. There are many that do not yet meet the licensure criteria, whom nevertheless recognize a code of mutual respect for neighbors & other hobbyist, the art of assembling a clear station & the joy of a dying social phenomenon known as conversation. Then there are others that never were exposed to these values. Their primary joy of owning/ using a radio hovers on having the watts to step over the signal of others. Often, the only form of intelligence sent through their carriers is a distorted “squashed you”! If you were raised accepting athletes that only win by using steroids, car racers cheating with illegal fuels, artists dubbing rather than singing and other examples of eccentric narcissism, then, you will be persuaded that squeezing 250W out of a 100W transistor is an acceptable (perhaps noble) challenge. Rather than cringing at the thought of harmonics, mature hobbyists should seize the moment to entice prospects into the enjoyable, law-abiding and purposeful part of this hobby. What you do for you die with you, but what you teach and do for others lasts forever. 73's

 

[The Mad Scientist]

I agree wire dawg, However you can lead a horse to water but you cannot make it drink.

You can preach this word till you are blue in the face and it will be for nothing. The way you and many others see it is a dieing art. In anything that you want to learn you need to have a genuine interest to do it the right way....

Nevertheless I couldn't agree more.

 

[wavrider]

Well said.

QuOTE=Wire Dawg;409254]Academics & ethics get in the way of an answer. Seasoned hams & technicians that have witnessed the advances of electronics and cherish the science behind a clean signal quickly recognize the compromises that radio equipment manufacturers make for $$$. There are many that do not yet meet the licensure criteria, whom nevertheless recognize a code of mutual respect for neighbors & other hobbyist, the art of assembling a clear station & the joy of a dying social phenomenon known as conversation. Then there are others that never were exposed to these values. Their primary joy of owning/ using a radio hovers on having the watts to step over the signal of others. Often, the only form of intelligence sent through their carriers is a distorted “squashed you”! If you were raised accepting athletes that only win by using steroids, car racers cheating with illegal fuels, artists dubbing rather than singing and other examples of eccentric narcissism, then, you will be persuaded that squeezing 250W out of a 100W transistor is an acceptable (perhaps noble) challenge. Rather than cringing at the thought of harmonics, mature hobbyists should seize the moment to entice prospects into the enjoyable, law-abiding and purposeful part of this hobby. What you do for you die with you, but what you teach and do for others lasts forever. 73's[/QUOTE]

 

[psycho]

The 2x4 X-Force amp I have was originally biased Class "B" from X-Force. I found that the biasing was done very poorly (by design) and I removed their biasing, and re-biased everything myself. The transistors were biased at about .35 volts at the bases. Nowhere near close enough for AB1 operation.

I re-biased them using all Radio Scrap components, and they now run at about .62V at keydown. That brings it into AB1 territory. For info on the biasing, go into the homebrew section, and you'll see my thread on this conversion.

http://www.worldwidedx.com/home-brew/138726-x-force-amp-finished.html

The 600W was measured on a Bird 43A Thru-line wattmeter using a Cobra 2000 GTL doing 18W on SSB, to a Hy-Gain SP-500 with a flat SWR. I use Belden RG-8U solid center for coax.

Keep in mind that the input to the driver and final sections both are "padded". Note the resistors on the input transformer on the driver stage, and note the resistors in between the driver and final stages. Those resistors are "limiting" input wattage to a degree to reduce overdriving.

~Cheers~

I just don't understand the 2x4 B biasing concept. On ssb it will sound like complete shit because those amps don't require much drive for FULL output and on ssb that would be worthless. You turn the variable back and on ssb that 2 watt 100 ohm pot will smoke.
If you like ssb a 1x4 or 2x4 TNT B biased amp is a poor choice and they whoop ass on AM, but that defeats the purpose of buying a ssb amp.
I was driving a Magnaforce 1000 straight 6 pill with a Cobra 148 throwing 16 watts pep and the output was only 300 but it sounded great. On AM that amp rocks the house.
I know on this forum "Blaring Loud" AM audio is frowned upon and puts Booty in lecture mode, but different strokes for different folks.
Crappy SSB is as worthless as a box cutter in a gun fight.
With CB radio popularity on a nose dive, do I care if my set up scatters a few channels....hell no! Not a soul will complain if nobody is on the radio.

 

[BOOTY MONSTER]

i'm definitely a fan of loud audio ... when it's understandable . but i hate the chit4brains folks who over-modulate so bad they have to repeat themselves .......... and/or i hear them on nearby (or not so nearby) channels miles away .