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DX959 (new MOSFET version) dual final mod?

loosecannon

loosecannon

Sr. Member
Mar 9, 2006
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just had a thought, (someone not the date and the time! LOL)

is there a dual final mod out yet for the new MOSFET version of the DX949/959 chassis?

just guessing here, but if done up right, i think this new radio could do more than 60 watts PEP!

truely a "sleeper".

i only wish i had the knowledge required to figure it out myself.
:?

any and all input welcome,
loosecannon
 

well, it looks as though there's either not much interest in this mod, or there's not much info out there about it.

so, ive decided to try and figure it out for myself by comparing the schems. of the MOSFET DX959 to the MOSFET DX2517, which uses dual MOSFET finals and what seems to be an otherwise identical amp section.

from what i can tell; the parts that need to be added are:
Q48 (IRF520)
D91 (5V6)
R242 (100K)
R243 (47K)
L34 (1K) ((resistor with ferrite bead on one lead))
C209 (.0015uF)
C211 (.1uF)
C212 (.1uF)
VR11 (100K)

to me it seems like you could just add these parts, rebias the driver and finals, and be done with it.
if there are some jumpers or other parts that need to be removed, im not seeing them.
oh, and it looks like the chokes going from the power plug to the board will have to be upgraded to heavier guage wire wrapped around a ferrite bead, along with adding a heatskink to the back of the radio.
looks like the holes for the FCC plate will be the holes for mounting the heatsink.

can anyone add any info or experience to what i have "guessed"?

DTB, have you done any of these yet?
GRTS, are these boards identical in this respect?

thanks for any and all info on this.
sure hope it works out.

yes, i am aware of all of the cost/perfromance arguments.
this is not about cost to me; its about my specific installation, and trying something new!

PS- do the dual IRF520's need to be a matched pair?
thanks,
loosecannon
 
loosecannon said:
well, it looks as though there's either not much interest in this mod, or there's not much info out there about it.

so, ive decided to try and figure it out for myself by comparing the schems. of the MOSFET DX959 to the MOSFET DX2517, which uses dual MOSFET finals and what seems to be an otherwise identical amp section.

from what i can tell; the parts that need to be added are:
Q48 (IRF520)
D91 (5V6)
R242 (100K)
R243 (47K)
L34 (1K) ((resistor with ferrite bead on one lead))
C209 (.0015uF)
C211 (.1uF)
C212 (.1uF)
VR11 (100K)

to me it seems like you could just add these parts, rebias the driver and finals, and be done with it.
if there are some jumpers or other parts that need to be removed, im not seeing them.
oh, and it looks like the chokes going from the power plug to the board will have to be upgraded to heavier guage wire wrapped around a ferrite bead, along with adding a heatskink to the back of the radio.
looks like the holes for the FCC plate will be the holes for mounting the heatsink.

can anyone add any info or experience to what i have "guessed"?

DTB, have you done any of these yet?
GRTS, are these boards identical in this respect?

thanks for any and all info on this.
sure hope it works out.

yes, i am aware of all of the cost/perfromance arguments.
this is not about cost to me; its about my specific installation, and trying something new!

PS- do the dual IRF520's need to be a matched pair?
thanks,
loosecannon
Click to expand...

Both main PC boards appear to be close enough in this respect.
You seem to have most areas covered.
Remember to change out coil L35 to a 4 turn for dual finals and add the a 47pf in C202 on the output.

Then adjust VR11 for 3.65 volts in SSB TX on the bare lead of the 1K resistor at L34.

That should certainly get you in the ballpark.

Don't worry about matched pairs with IRF520 mosfets when adding the second final. Just make sure you're drawing about 100~150ma total across TP7 to TP8 in SSB TX with the 3.65 volts on both 1K resistors at L34 & L33 by adjusting VR10 and VR11 respectfully.

-Ray
 
Hope you do not mind that I moved it to the modification section, this seems like a great mod and thus would be a great section to keep it alive.

Thanks guys!
 
not a prob. hamer.

GRTS, thanks once again!
i think i owe you at least a six pack by now.LOL

parts will be in the mail by wed., so i may get to try this over the weekend.

oh, this 4 turn coil you speak of; is it something i can buy from mouser or jameco etc... or is it a galaxy specific part?
IOW, where can i get one?

cant wait to try this.
i am surprised at how little interest there is in this mod, i thought this was the most popular CB going these days.
go figure.
maybe everyone is waiting until i post that no smoke came out of the radio to try it.LOL

i will post back when i try it.
loosecannon
 
loosecannon said:
not a prob. hamer.

GRTS, thanks once again!
i think i owe you at least a six pack by now.LOL

parts will be in the mail by wed., so i may get to try this over the weekend.

oh, this 4 turn coil you speak of; is it something i can buy from mouser or jameco etc... or is it a galaxy specific part?
IOW, where can i get one?

cant wait to try this.
i am surprised at how little interest there is in this mod, i thought this was the most popular CB going these days.
go figure.
maybe everyone is waiting until i post that no smoke came out of the radio to try it.LOL

i will post back when i try it.
loosecannon
Click to expand...

You can find the 4 turn in any dual final Galaxy chassis radio if you have one laying around for parts. If not you can use some good ole ingenuity and convert your 7 turn to a 4 turn easy enough.

8)
 
The 959 is a nice radio. If the new version tunes up nice as is why monkey with it? If it can already do say 40-45 watts then 50-60 would serve no purpose and no one would even notice.
 
my radio does about 28-30 watts PEP.
i guessed at the 60 watt figure.

the question of "why monkey with it" never occurs to me.
i bought this radio with the specific purpose of modding it, experimenting with it, and seeing what it can and cant do.

thats the most fun part of the hobby for me.

i had been reading alot about the 25/29 chassis and the MOSFET mods, so i bought a PC68XL for 50.00, did the MOSFET mod, the receive mod, gave it a full alignment, and sold it to a friend for 100.00.

this is just what i do.

i am very hip with the 4X power increase for 1 S-unit business, i just want to see if i can do it.

GRTS, thanks!
i was hoping you would say that i could cut my 7 turn down to a 4 turn.
parts order got put on hold, but i will be trying this.
will post results when done.
loosecannon
 
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Thats pretty cool that you can do that, and I see what your doing now. I guess what I just laugh at is some drivers for example, they get a new radio that is working and sounding like it should and then every other truck stop they stop at they have someone tinker with it over and over.
 
Good luck with your efforts this weekend loosecannon!! I will be watching for you to post the results (I love to tinker also) I seen a bumber sticker the other day that read "If it ain't Broke..Fix it till it is"!!!! Hell Ya :) Hope it works just like you planned, Hooty
 
oh man Butcher318, i KNOW what you are talking about.

i used to do a fair amount of modding and "peaking" radios for locals around here. (what a headache!)
most times, it was re-doing what the owner had tried to do himself.
i didnt know what the heck i was doing, but the radios i tuned sounded good!
i had to tell one guy that i would not do work for him anymore, because as soon as i gave the radio back to him, he went inside and screwed it up again. DOH!!!

hooty,
this mod has been put on hold for a while.
some things here at work have broken, and i must keep my focus on them.
i will post when i do try this, but it may be a while.
wanna go first? LOL
loosecannon
 
Mosfets sound like doo doo , they have horrible audio characteristics in am radios, like their all in or all out, I have never heard a mosfet conversion in any rig sound good, realy, but good luck! Let us know how it comes out!
 
GRTS

Ive been doing this for quite some time. Thanks for the info on dropping the coils. Ive got em doing another 10 watts now. 55 w PEP.

I noticed that you mentioned you dont have to use a matched pair of transistors....I dont know about that. I have found that all IRF520s are created =. When I do a dual final mod to an already mosfet 959, I move the driver to the other final slot and replace the driver with another IRF520. I suspect the 2 came out of the same lot. I also pull the IRF520 in the final position and regrease it (sometimes the factory does not put enough grease on em). Believe me, I have about 20 different lots of IRF520s by different mfgrs and with different part numbers. The first one I did I used an IRF520V with the stock one and puff the majic draggon! Later I found the IRF520Vs I was using were kinda low mosfet on the todem pole and did not match the other final well.

If I so an older unit, I leave the driver alone and replace only the 1969 with 2 FETs. The 2166 is a bit lighter drive than another FET, but I dont think the extra work to redo the entire driver section is worth the 5 watts I see on the meter.

I have a ? though about the VRs at 10 and 11. Mabee GRTS can interlude here and put my quest for answers to a rest. Is it necessary to use a 100k Ohm pot? or can 50K be used without the 100K Ohm resistor? I have received mixed signals about using 50K Ohm (I have a bunch of 50K Ohm pots and very few 100K Ohm pots)
 
skirtchaser said:
Mosfets sound like doo doo , they have horrible audio characteristics in am radios, like their all in or all out, I have never heard a mosfet conversion in any rig sound good, realy, but good luck! Let us know how it comes out!
Click to expand...
I could do a mosfet upgrade in a Cobra 29 and you would never be able to tell the difference from the one done with the 1969. Hundreds done....NO audio complaints!
 
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