For those trying to get more out of a single mos fet final converted to dual final, As in the DX959, replace Q52 with a 2SC1973. Replace R-253 with a 22 Ω. Adjust L40 and power
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
A Winner has been selected for the 2025 Radioddity Cyber Monday giveaway! Click Here to see who won!
Galaxy schematic-959 duel final
- Thread starter Larry A McClanahan
- Start date
Good transistor but can't drop it in to a mosfet circuit. The 2sc1973 Replacement doesn't even have to have the resistor replaced. You can just retune the can and get better performance.
I attempted dual finals long ago with a mosfet 959 and if I remember it wasn't anything special when it was finished. Between 35 to 40 pep so it really wasn't worth the work in my case. Later I did a 939 mosfet and it did much better but maybe because there's some capacitance differences being it's am only. For me it turned better results converting the old 3600 boards from single bipolar to dual mosfets once the bipolars got too pricey.
Last edited:
I run something that most would hit with a driver. I don't want to do that. 40+ watts works for me. Switching to the 2SC1973 Will increase the output of each transistor in the RF chain.
I am gathering the components to add a second transistor.
after reading this i ordered some 1973s. got a 959b that i'm converting to a dually by copying the schematic of a 2517/99v output section instead of doing the cbtricks method
Ronnie,
This is how i figured out the dual final mod for the 959 many years ago.
do be careful though, as the jumpers are not all shown in the diagrams and can confuse things.
also, that little coil needs to be converted from a 7 turn coil to a 4 turn coil.
LC
This is how i figured out the dual final mod for the 959 many years ago.
do be careful though, as the jumpers are not all shown in the diagrams and can confuse things.
also, that little coil needs to be converted from a 7 turn coil to a 4 turn coil.
LC
my 959b has a 390pf cap on both sides of it stock off the floor. where would i get this coil or the dimensions of it? getting around 30ish watts with both finals in.
one of the pots is not reaching 4v at max. maybe both finals sitting at 3.02v has something to do with that.
one of the pots is not reaching 4v at max. maybe both finals sitting at 3.02v has something to do with that.
L35 is the coil you need to remove the turns from.
this one:
DX959:
2517 (has dual finals from the factory)
and here is the thread from almost 20 years ago where i did this to my 959.
man i have been on this forum a long time LOL!
sorry that the thread kind of drops off of a cliff, i must've moved on from it right after i got it to work and never posted my results.
GRTS in that thread was an actual tech at Galaxy radios and his advice should be heeded.
TheDirtMover is also a well known shop owner that is still in business today and knows his stuff.
hope this helps!
LC
this one:
DX959:
2517 (has dual finals from the factory)
and here is the thread from almost 20 years ago where i did this to my 959.
man i have been on this forum a long time LOL!
sorry that the thread kind of drops off of a cliff, i must've moved on from it right after i got it to work and never posted my results.
GRTS in that thread was an actual tech at Galaxy radios and his advice should be heeded.
TheDirtMover is also a well known shop owner that is still in business today and knows his stuff.
hope this helps!
LC
I remember several trying this mod around the time the dual mosfet rigs came on to the scene. Everyone wanted a dual final 949, 959 with the power of the 10 meter siblings. I tried it as did many others and the common complaints were that they just wouldn't achieve the 50 pep that the 10 meter siblings could. If I remember correctly 30 to 35 pep was about it and so many of us abandoned the idea instead.
I remember even after swapping coils and such, making some capacitor changes etc. there was still something everyone was missing to make it perform well. I abandoned my project and sent it down the road
That was probably 15 to 20 years back.
I remember even after swapping coils and such, making some capacitor changes etc. there was still something everyone was missing to make it perform well. I abandoned my project and sent it down the road
That was probably 15 to 20 years back.
thank you loosecannon. the 7t is still in there. gonna give it a whirl. radios already decked out with channels, unlocked clarifier, so now it's getting duals and im gonna try the (more involved) swing mod at the pre-driver stage like in that thread. setting it up to drive a big box
Please report your findings.
I thought that coil was there as an RF choke only, but if that brings up the power, it must be serving some inter-stage matching function too and I am struggling to understand how. Please let me know if it does bring up the power so I know if I need to chase down the reason why.
On the surface, it seems like reducing the turns would reduce the reactance and allow more of the driver's RF to go to ground via C213 leaving less for final drive. IDK. Tomorrow I might play around with simsmith and try to figure it out.
It would make more sense that changes would be required after the finals. Paralleling them would essentially half the output impedance of the finals throwing off the match. That would require a change in the output network. I see that there are differences in that area between the 959 and 2517 (L30, C195 and C192).
I briefly read the thread loosecannon referenced and I get the impression all of the kinks haven't been worked out completely. Unrelated: I did see 8113 was part of that thread and I wonder how he is doing. I sold him back his Icom and box about 2 years ago and haven't heard from him since. I hope he is doing ok.
Brandon i couldn't tell you why that coil is different in the "FCC certificated radios" as opposed to the 10 meter rigs, i just know that it was an actual service tech who worked at Galaxy that told me to do it.
as for the dual final mod working, it definitely did, and i know it was doing over 50 watts PEP but i cant remember how much exactly.
I had the same issues as others where the radio acted as if the second final wasn't even there, but it was so long ago i can't remember what fixed that issue.
i do remember that adding the external heatsink is necessary.
comparing the schematics of the mosfet 959 with the mosfet 2517 you can see that they made a special note about the 2517 being 4 turns.
959:
2517:
LC
as for the dual final mod working, it definitely did, and i know it was doing over 50 watts PEP but i cant remember how much exactly.
I had the same issues as others where the radio acted as if the second final wasn't even there, but it was so long ago i can't remember what fixed that issue.
i do remember that adding the external heatsink is necessary.
comparing the schematics of the mosfet 959 with the mosfet 2517 you can see that they made a special note about the 2517 being 4 turns.
959:
2517:
LC
I did see the note about the turns and that's why I tried to wrap my head around it (and failed). I don't have time to go down the rabbit hole tonight but I do plan on trying to figure it out soon. The only smith chart software available to me at work is online so I didn't even bother earlier. I have no doubt they did it for a reason though and when I come up with a reasonable explanation, I will share my thoughts here.
so i just rewatched the youtube videos that stickman did with his 959's and it appears he left that 7t coil alone and got the juice out of em. im wondering how he went about it