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FatBoy 6 Pill
- Thread starter 5 X 5
- Start date
Well the FatBoy seems to be humming right along. Only one light though, hoping the other light comes on when you put the juice to it? The $5 Magnum S3 seems to work also. Well it did before I hooked up the FatBoy, then it blue the fuse. Everything was turned off when I hooked it all to the battery. Guess I will swap it and try again. Not familiar with the S3 but pretty sure someone has been inside. The meter changes color and looks like a bypass or 2 might have been made. Will pop open again for a pic or 2. I saw a loose grey wire that could be shorting on the chassis? Had scotch tape on it so who the hell knows...?
Replaced 2A with 6A fuse and we are a go. Tuned in scanner and I am broadcasting, but with the crappy configuration I threw together I don't want to key down for more than a couple seconds. 
Aren't all 6 pill amps arranged like 2x4? If so, you will drive the snot out of the two driving pills by too much. They would not - by design - need any more than 20w into the amp to fully overdrive the four.
Never understood how a builder can build that kind of arrangement. If two 2879 pills are driving four; then that means they will have approximately ~275w driving four 2879 pills that only require no more than forty watts to reach full output of ~475w. SO; what is the point of diving them so far. After all - all the wattage output more than ~475w would be crap watts and nothing I would be proud of by any means.
I know a couple of guys that bypass the first two pills and just drive the four with 40w and have a real clean, loud station.
Not meaning to rain on your parade, just wondering why the amp builders did this?!?
Not without blowing up either the two driver 2879s or the output 2879's - or both.
maybe they are counting on a return customer - lol?
Never understood how a builder can build that kind of arrangement. If two 2879 pills are driving four; then that means they will have approximately ~275w driving four 2879 pills that only require no more than forty watts to reach full output of ~475w. SO; what is the point of diving them so far. After all - all the wattage output more than ~475w would be crap watts and nothing I would be proud of by any means.
I know a couple of guys that bypass the first two pills and just drive the four with 40w and have a real clean, loud station.
Not meaning to rain on your parade, just wondering why the amp builders did this?!?
Not without blowing up either the two driver 2879s or the output 2879's - or both.
maybe they are counting on a return customer - lol?
The way it's all balun-ed out - it's pretty much spread across the board...
Considering even for a moment the math of 100% transference of power evenly across all six - it can easily handle any high-drive radio - and that's at 100% coupling (matched) efficiency.
I'm led to believe this was a comp amp so no guarantees on any linearity.
The one of the few amps I've seen built from older technology that has properly wound input and output couplers.
So, yeah, if you've got an SWR meter - great, but even better is an MFJ-259 to see what you may need if anything to properly match the input. And can also help in determining the needs for any re-work of the output.
But even then it is possible that with even a 50 ohm load - the possibility of 33 ohm or even 25 ohm output matching the SWR on the output side should be tolerable for those 2879s'.
And this is all presuming that none of the pills from any initial test had popped.
Considering even for a moment the math of 100% transference of power evenly across all six - it can easily handle any high-drive radio - and that's at 100% coupling (matched) efficiency.
I'm led to believe this was a comp amp so no guarantees on any linearity.
The one of the few amps I've seen built from older technology that has properly wound input and output couplers.
So, yeah, if you've got an SWR meter - great, but even better is an MFJ-259 to see what you may need if anything to properly match the input. And can also help in determining the needs for any re-work of the output.
But even then it is possible that with even a 50 ohm load - the possibility of 33 ohm or even 25 ohm output matching the SWR on the output side should be tolerable for those 2879s'.
And this is all presuming that none of the pills from any initial test had popped.
Thanks again for all of the info. I don't have the proper test equipment you suggest and even if I did it would still be a learning experience for me. There are a couple shops not too far from where I pass by in Ft. Worth from time to time. One has horrible reviews but the other shop can't seem to get enough praise from what I have found. May call over there once they open and see about getting a checkup. I have only fired it up to see the fan/lights run and keyed down for no more than a second or two. The coax might not be in the best shape but no exposed or weak areas that I see, so fingers crossed all checks out.
It'll be a bit of work, but using a Dummy load with at least 100W capacity would help here.
That type of capacity isn't always up on a shelf in a cupboard at home for a lot of people.
IF you were able to apply power and it didn't pop any fuses - you can go along and check the pills but be careful not to short leads of your test equipment against any two parts - this design uses a "sandwich" method of standoffs.
The big copper board is the "mounting plate" and basic RF and Supply grounds together - means the standoffs are floating at their own level of voltage - makes it easier to check - you just check the "lands" of the standoffs to ground and note the readings on the Voltmeter side of your DVM.
What you look for is consistency amongst the positions of those standoffs.
The longer ferrite/tube and board combos of your RIGHT -edit side, are the combiners - they route outputs power thru the tube itself then into ground - the wire coil winds inside the "cores" are what goes out as RF.
There is a ratio windings on these things to meet the transistors' best match output to the impedance the user set up the combiner for - in this case looks to be 50 ohms - on each one of those output combiners.
These twin sets, are self-contained amps, by themselves. So they take their product (output) and place IT INTO THE COMBINERS. The user then attempts to recoup that energy by matching each combiner together into on output.
Now, what some people have done is taken the winds of wire in these cores to the extreme - as you add winds you increase the impedance matching (expected impedance) - so amongst 6 of them - with three combiners - you'll wind up with some pretty low numbers in parallel form - like a little less than 17 ohms impedance over the whole mess.
With all things equal - I presuming 50 ohms / 3 sets = 16.67 ohms reactive.
On the amp - I did not see a solitary combiner - so what that means is each output power combiner may have to be re-wound with an extra turn or two of wire - nothing too much just enough to raise the expected output impedance so that when you combine all three in parallel form - they're closer to the 50 ohms expected.
I'd look at 150 ohms expected, 50 ohm x 3 = 150 - so you may have to redo all those output winds to rework the simple combiner network into a 150 ohm per pair - up to the 50 ohm parallel output - but we don't know what you have until the MFJ-259 can be thrown in to make sure, that either, the calculations are already done, or, do we have to add more to make the amp a 2X3 = 6 out style...?
You guys can flame away if you must, but the premise here is to make the amp survivable in everyday use - at least that is my intention - your mileage (and attitude) may vary...
That type of capacity isn't always up on a shelf in a cupboard at home for a lot of people.
IF you were able to apply power and it didn't pop any fuses - you can go along and check the pills but be careful not to short leads of your test equipment against any two parts - this design uses a "sandwich" method of standoffs.
The big copper board is the "mounting plate" and basic RF and Supply grounds together - means the standoffs are floating at their own level of voltage - makes it easier to check - you just check the "lands" of the standoffs to ground and note the readings on the Voltmeter side of your DVM.
What you look for is consistency amongst the positions of those standoffs.
Tapped and checked across to ground - each land has a voltage - each standoff position of the individual twin pair amps should have the same readings across all the same lands in the same position of the twin pairs - if the rear combiner lands all except one have the same idle reading (you apply power no signal ok?) then that pairing is suspect as possibly being bad - more than 2 tenths of a volt may indicate unequal current power flow in that pair and it needs to be checked, same for the base input idle power too, for each pairing - all lands should be checked to ground and note the reading - any variances should be re-verified and checked out for soldering and part location/trimming.
Note the power feed system - one side has all the battery cable and power feed. The couplers, those ferrite/tube and boards mounted on their own standoffs - the smaller size (in your pics the ones to the LEFT - edit) are input splitters - they DIVIDE the RF power equally to the bases' of the two transistors.
The longer ferrite/tube and board combos of your RIGHT -edit side, are the combiners - they route outputs power thru the tube itself then into ground - the wire coil winds inside the "cores" are what goes out as RF.
There is a ratio windings on these things to meet the transistors' best match output to the impedance the user set up the combiner for - in this case looks to be 50 ohms - on each one of those output combiners.
These twin sets, are self-contained amps, by themselves. So they take their product (output) and place IT INTO THE COMBINERS. The user then attempts to recoup that energy by matching each combiner together into on output.
Now, what some people have done is taken the winds of wire in these cores to the extreme - as you add winds you increase the impedance matching (expected impedance) - so amongst 6 of them - with three combiners - you'll wind up with some pretty low numbers in parallel form - like a little less than 17 ohms impedance over the whole mess.
With all things equal - I presuming 50 ohms / 3 sets = 16.67 ohms reactive.
On the amp - I did not see a solitary combiner - so what that means is each output power combiner may have to be re-wound with an extra turn or two of wire - nothing too much just enough to raise the expected output impedance so that when you combine all three in parallel form - they're closer to the 50 ohms expected.
This is why I recommend the MFJ-259 or someone with some amp experience to help you set up and calibrate the amp to make it work as an everyday linear amp - it's possible - just you may have to rework some sections.
This is all SPECULATION until you see / determine - if the combiners were already re-worked to develop a 150 ohm output - then the amp builder has done their job and it's up to you to use it right.
This is all SPECULATION until you see / determine - if the combiners were already re-worked to develop a 150 ohm output - then the amp builder has done their job and it's up to you to use it right.
I'd look at 150 ohms expected, 50 ohm x 3 = 150 - so you may have to redo all those output winds to rework the simple combiner network into a 150 ohm per pair - up to the 50 ohm parallel output - but we don't know what you have until the MFJ-259 can be thrown in to make sure, that either, the calculations are already done, or, do we have to add more to make the amp a 2X3 = 6 out style...?
You guys can flame away if you must, but the premise here is to make the amp survivable in everyday use - at least that is my intention - your mileage (and attitude) may vary...
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Damn. Printed out.
Jesus Handy Andy I wish you lived in my neighborhood. I would sure love to get down the basics. I have a couple dummy loads from back when I tested a few old tube radios, but like I said earlier all packed away, and the know-how is even further packed away. This is something I want to leave to a pro. Just got off the phone with Kilgore's Electronics in Fort Worth and he can do a bench test at no charge while I wait. Says to even bring the radio I plan on using. From what I hear and read here, he is THE guy to go to with anything radio related. Lucky me again!
Jesus Handy Andy I wish you lived in my neighborhood. I would sure love to get down the basics. I have a couple dummy loads from back when I tested a few old tube radios, but like I said earlier all packed away, and the know-how is even further packed away. This is something I want to leave to a pro. Just got off the phone with Kilgore's Electronics in Fort Worth and he can do a bench test at no charge while I wait. Says to even bring the radio I plan on using. From what I hear and read here, he is THE guy to go to with anything radio related. Lucky me again!
WOOF - figures I went and looked on my notes, well, blew that - the "INPUT" is on the left (smaller single cores) the OUTPUT 1s on the RIGHT by the battery cable.
I was looking at your pics and I oriented them so I could see some details - and of course as I got back on here to post the message - I had my notes and pic oriented in a way for me to view it and give you these notes...which was backwards to yours...
Here's a better worded way of looking at it using your pic so you can see what and where I'm talking about...
Reprint my post so you can review with the tech, else he will have the pic oriented the wrong way - he'll know what to do either way. But I had D/l'd your pic to enlarge details to provide some guidance for you - just never remembered to re-check back to your pic over the post until I went back and reviewed your photos of it and compared - oops...
So for further elaboration - the "Green wire" in the pic is the "Bias" power choke - works with the 10 ohm resistors - this guy did a pretty good job of setting up a Class C amp - but the WHITE wires on the LEFT side that are part of the trio (triangle) is th splitter for the INPUT - you'll need to verify that the input chokes and splitter in the left (white wire trio) is properly setup to drive the 3 pairs - else that may need work so you can drive it with a high-drive radio without blowing up the radio from the poor SWR mis-match issue this could make...
The RIGHT side white wire arrive to what looks like a "Combiner" but it could be just a simple balun or your worse nightmare when it comes to matching - so those two areas are part of the INPUT (Left) and OUTPUT (Right) and they need to meet your 50 ohms so you can run that thing without blowing it up AND/OR our radio at the same time...
Just so you know, they ran 3 100 ohm 2W resistors to SWAMP this region so it looks better (via impedance) and any SWR reflections are also taken up in the resistor array that straddles the Balun/Combiner - so it may handle High-SWR ok, but it's the LEFT side I'm worried about - RED is INPUT winds - and OUTPUT winds and note their number of turns as well as length of wire used can help you decide what to do.
:+> Andy <+:
I was looking at your pics and I oriented them so I could see some details - and of course as I got back on here to post the message - I had my notes and pic oriented in a way for me to view it and give you these notes...which was backwards to yours...
Here's a better worded way of looking at it using your pic so you can see what and where I'm talking about...
Reprint my post so you can review with the tech, else he will have the pic oriented the wrong way - he'll know what to do either way. But I had D/l'd your pic to enlarge details to provide some guidance for you - just never remembered to re-check back to your pic over the post until I went back and reviewed your photos of it and compared - oops...
So for further elaboration - the "Green wire" in the pic is the "Bias" power choke - works with the 10 ohm resistors - this guy did a pretty good job of setting up a Class C amp - but the WHITE wires on the LEFT side that are part of the trio (triangle) is th splitter for the INPUT - you'll need to verify that the input chokes and splitter in the left (white wire trio) is properly setup to drive the 3 pairs - else that may need work so you can drive it with a high-drive radio without blowing up the radio from the poor SWR mis-match issue this could make...
The RIGHT side white wire arrive to what looks like a "Combiner" but it could be just a simple balun or your worse nightmare when it comes to matching - so those two areas are part of the INPUT (Left) and OUTPUT (Right) and they need to meet your 50 ohms so you can run that thing without blowing it up AND/OR our radio at the same time...
Just so you know, they ran 3 100 ohm 2W resistors to SWAMP this region so it looks better (via impedance) and any SWR reflections are also taken up in the resistor array that straddles the Balun/Combiner - so it may handle High-SWR ok, but it's the LEFT side I'm worried about - RED is INPUT winds - and OUTPUT winds and note their number of turns as well as length of wire used can help you decide what to do.
:+> Andy <+:
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Awesome thanks a million. Printed again and have the FatBoy and Magnum loaded in the truck. Kilgore's is only open until 1pm but I just happen to be getting off work tomorrow at 10am to register a boat I built (another time...) and hoping to make it before he closes for the day. After that, the estate sale I bought the amp from is supposed to open tomorrow with more stuff... Busy day with all kinds of outcomes. I bet nobody on channel 6 broadcasts from a boat! Hmm...
Prolly not, but then they may use Oil barrels tied together to form Rafts, Tugboats, Ocean liners even ...
Salt water tends to corrode those Mercury Reflectors they may need to use...
There's only so much Zinc and Brass they can use as electrodes in the water to replace the Lemon Twist they'd otherwise use to "power" such a device...
Inadvertently - of course...
Well the FatBoy checked out fine. (Boat passed registration too!) The Magnum 257HP by itself pushed about 75w peak. With it turned down to around 10w going into the FatBoy we were getting 800-850 watts at 13v. Which is probably around where I will run it for everyday use. I think the most amps we drew were around 60 with amp and radio combined, so my Ram alternator should be fine. Right? Going to just run a 5' Firestick for starters and see how it goes. I thought I might need more but Kilgore is good with it so I am too. We talked for an hour about all kinds of stuff, boats, radios etc. but he told me about a Ch 6 powerhouse that lives near me. Is King Arthur a member here or anyone familiar? Supposed to be sucking an ungodly amount of juice from the grid... Also stopped by the estate sale again, same old stuff, got a pair of heavy duty coax cables and a box of around 50 small router bits for $5. Now the fun part, the install in 100 degree blazing sun.
- No one is chatting at the moment.