schematic for fatboy 2 x 2879

[bettyeboop]

does anyone have this......I am looking for keying info .....some amps have a diode on the coil of the relay some don't.....I am burning the keying transistor. On one side of the coil there is the keying circuit.....on the other side can I just make it hot if not running var power....on this amp I am switching the unit on with the internal power supply......the amp board came out of a fatboy two pill. I Am interested in your favorite drawings if you do not have the fatboy drawings..maybe someone can open theirs up and draw it out for me

I have noticed that between the pos and output of 2879's is around 700 ohms. I have several pills that need checking......Is this test valid.......can I ck them out with my scope?

I am building two amps and power supplies.....one is one hundred fifty amps out...

These questions need to be answered before I start on my 8 pill.
Whew.......I am disabled and love this stuff....hours go by......

#also interested in temp control for bias.......can not remember where I saw this.....think it was from Bob.

thanks for your help...... sorry for so many questions.....there is no one in this area to help me.

Please reply here or email if site is down.


Thanks again for the great knowledge base here.....hundreds of years of experience...awsome

galyn davis.......galyndavis@yahoo.com

 

[GRTS]

Hmmm, haven't been able to find any of those either. Maybe they are classified.

 

[bob85]

bettyeboop the diode across the relay coil is to supress back emf when you unkey, it stops the coil from zapping the keying transistor, most everything with a coil driven by fets or transistors from car fuel injetors to homebrew cb amps use them to protect the driver device, i would always use one,
yes one side of the relay coil is connected to the supply when the amp is turned on, the other side is grounded through the keying transistor when you key, try looking on wwpdx i think 521 still has the keying circuit schematic from his xforce posted there,
to test the transistors you need a meter with diode test function, unsolder the base and collector of one transistor in the pair and the base of the other then follow the instructions on how to test a transistor posted somewhere on here, its not foolproof but in most cases it works,

i have done several different thermal tracked bias circuits for myself and other folk, i drew them in windows paint but i dont know what i did with the schematics right now, they may be on a disk somwhere but i aint sure,
linearone posted a beefed up version of one of them on the old wwrf for the amp he built for bcrew, no idea if that will be transfered over here eventually,

you may be thinking of the bias boards i made based on a modified class AB/C version of motorollas aplication notes, not the easiest of circuits to make work right in a rf environment, maybe your thinking of the much simpler circuit i used to bias the 2x2879 that worked no problem and tracked ok, thats on the old forum but i never posted the schematic,
it would not be prudent of me to post shematics of the dave style amplifier but if somebody takes you some pics of their own amp thats up to them,

dont know if this link and pic will work here but here goes.

maybe you mean these

http://s5.photobucket.com/albums/y152/ukmudduck/2pill%20ab%20from%20used%20parts/2pill%20ab%20from%20scrap%20amp/

http://s5.photobucket.com/albums/y152/ukmudduck/b300p/?mediafilter=all

http://www.communication-concepts.com/appnotes/AN758300Sharp.pdf

 

[bob85]

i think this should be in the cb section, the zetagi will work from 80-10mtrs but its no ham amplifier

 

[bettyeboop]

bias circuit

thanks so much bob for your quick response. good reading looks like.

would you tell me how to do the simple bias trick you or someone was talking about.....much simpler than building the module. pill gets hot and turns gain down.......it is so simple you can just tell me how to do it. i JUST cant remember.

bob i can call you for almost nothing....i have vonage service. I think what I am talking about you can just describe it here.

many many many thanks
davis

 

[Scotie119]

I'm trying to repair my 5 pill Fatboy amplifier but can't find a spec sheet indicating component values.
can anyone help me with this? A schematic might help too.
Thanks

 

[Pioneer621]

I'm trying to repair my 5 pill Fatboy amplifier but can't find a spec sheet indicating component values.
can anyone help me with this? A schematic might help too.
Thanks

They are fairly simple amps, perhaps post a few clear photos of the parts in question and someone can probably help.

 

[AudioShockwav]

You are not going to find a schematic from the builder, Fat Boy, X Force, Dave made and all of the others don't provide one..... I don't want this to sound too bad but some of these comp style amps were " monkey see monkey do " type of builds with the Labor not understanding the device they were building.
When Carl was building X Force you got a single page sheet with recommendations on how to run the amp, and that was it.
At least he told you drive levels.

As Pioneer said, post up what you are dealing with and photos will help us, help you.

73
Jeff

 

[9C1Driver]

I'm trying to repair my 5 pill Fatboy amplifier but can't find a spec sheet indicating component values.
can anyone help me with this? A schematic might help too.
Thanks

As stated, when it comes to the dozen er so custom built "comp style" amplifiers none of the builders would provide a schematic ever. Some would go so far as to sand off the part names and numbers because they did not want someone to copy their amp. You don't get much when your talking about an illegal product that is not FCC approved. The "spec sheet" you would get would state the finals it had, class of the amplifier, recommended drive levels, and wattage output at a given voltage. That's it.

 

[groundwire]

Try asking ica, they just might tell you, maybe. Its a long shot but you never know

 

[Crusher]

Which 2sc2879’s are you referring to? HG, RFP or Toshiba? Different values on the HG versus the Toshiba. Also what transformers are being used? Fat boy was using comp ( 5/8” x 1.25”) but lately they have been using the smaller 1/2” diameter 61 material. Usually 1.25” but I have seen some 1.5” length. ( I don’t like because the smaller stuff seems to saturate much easier). Sometimes on the ones in trucker case ( no fan) I have even see 43 material. Too many variations to just throw out values.

 

[nomadradio]

There was a primitive e-book type file out there ten or so years back, "Build your own linear" or something like that. If that's still around out there, this is as close as you'll come.

73

 

[Crusher]

Also worth mentioning, sometimes you can find RMC / Mallory ceramic capacitors on eBay. I have bought several over the last few years. Usually N750 or N1500 @3kV rating. They work great in 4pill / transistor sections. Never had one fail yet. Tedss.com has some decent stuff if you spend the time searching. Much better than Mouser.com pricing or ICA.