Go Back   WorldwideDX Amateur Radio Forums > Citizens Band Related > CB Radio Modifications


Amateur Callsign Lookup
Enter Callsign:

Galaxy Dx 959 Mosfet Complete Tune Up Procedure

Like Tree2Likes

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 03-13-2010, 07:37 AM
Wire Weasel's Avatar
Senior Moment
iTrader: (17)
 
Join Date: Dec 2008
Posts: 2,679
Wire Weasel is on a distinguished road
Default Galaxy Dx 959 Mosfet Complete Tune Up Procedure


Anyone know where this is located on the internet or know how to do it and can post here?


This would be for single final mosfet in the current edition 959. We all know they can be modded-peaked for the neighborhood of 30-35 watts.

But there's much more to it than turning the power pot. Several things have to be done.

Anyone know the whole procedure?

Yes there is a Service Manual at cbtricks but that's just for achieving factory specs. Doesn't help with the full power-peak modification.

This is not for my 959. It has already been done. There are several guys in my area that are considering this radio. A local pro tech at a truck stop in the area is the go-to guy to get these things stroking but of course he won't tell anyone how to do it.

TNX !!
__________________
Welcome to the WWRF. Plenty of Free Parking and with 5,000 posts you get egg roll


Reply With Quote
  #2  
Old 03-13-2010, 09:25 PM
loosecannon's Avatar
break on through
iTrader: (1)
 
Join Date: Mar 2006
Posts: 1,876
loosecannon is on a distinguished road
Default

there's actually not that much to it.

these radios are primed to be loud and only need a few adjustments to get there.

the MOSFET versions have already had the parts upgrades done at the factory, so no need to replace the 2SB754, its already been done!

the first thing to do is make sure the transmitter coils are peaked for max PEP wattage.
turn the RF power control all the way up, and on channel 20, AM mode, mic gain all the way up; adjust L40, L42, L43, and L44 for max watts while saying "ahhh" into the mic.

(the one i had didnt need any adjustments, as they were already peaked. your mileage may vary)

now make sure the power is somewhat equal on channels 1 and 40.
if not, use L40 and L42 to balance it.

now set VR14 for about a 5 watt deadkey. (yes, you can do more, but why? no one will notice and it will just heat the radio up more.)

turn the RF power knob all the way down and set VR18 for 1 or 2 watts. whatever you like.

now turn VR16 (AMC) all the way up.

you can set VR13 (SSB ALC) for about 15 watts if you want, but there really is no need.

the only "mod" i would suggest, and you might not even need to do it, would be to add a silicon rectifier diode (1n4001 etc...) to R264.
this is what is commonly called the "swing mod."
R264 is right near VR14.
lift the leg of R264 that is closest to T1 and insert the banded end of the diode in the now empty hole.
solder the other end of the diode to the loose leg of R264.

thats it!
you should have a very loud radio after performing these steps.

LC
__________________
https://i.chzbgr.com/maxW500/1912864512/h0491035C/

Reply With Quote
  #3  
Old 03-14-2010, 06:56 AM
Wire Weasel's Avatar
Senior Moment
iTrader: (17)
 
Join Date: Dec 2008
Posts: 2,679
Wire Weasel is on a distinguished road
Default

I know the techs usually spread the one coil in the middle of the board and don't you have to adjust the bias on the mosfet or something like that? At any rate I absolutely appreciate the info here LC ! Will print this out and give it a go next time I'm asked to look at a new one! You da man!
__________________
Welcome to the WWRF. Plenty of Free Parking and with 5,000 posts you get egg roll

Reply With Quote
  #4  
Old 03-14-2010, 09:23 AM
Senior Member
iTrader: (1)
 
Join Date: Dec 2008
Posts: 212
JoeDirt is on a distinguished road
Default

Set the bias on a mosfet at 3.5-4 volts, I think they come at 3.5 from the factory!

Every radios different sometimes your spread the coils and sometimes you don't!

Reply With Quote
  #5  
Old 03-14-2010, 09:45 AM
Wire Weasel's Avatar
Senior Moment
iTrader: (17)
 
Join Date: Dec 2008
Posts: 2,679
Wire Weasel is on a distinguished road
Default

Thanks JD ! Loved your movie by BTW ! Uh.....anyway you could hook me up with Brittany Daniels?
__________________
Welcome to the WWRF. Plenty of Free Parking and with 5,000 posts you get egg roll

Reply With Quote
  #6  
Old 03-14-2010, 09:46 PM
loosecannon's Avatar
break on through
iTrader: (1)
 
Join Date: Mar 2006
Posts: 1,876
loosecannon is on a distinguished road
Default

i also loved JoeDirt! future cult classic LOL.
i met David Spade once backstage, and told him i was a fan of that movie.
he said, "really!?" LOL

wire weasel,

yes, i forgot to mention biasing the MOSFETs. really, unless someone has messed with them, they should be fine, but if you want to get them just right, its not too hard to do.

as far as spreading the coils goes, everyone seems to have their own stance on this.

mine is based on what these coils actually do.
L30, 29, and 28 form whats called a "half wave filter". a half wave filter's job is to filter out harmonics while at the same time maintaining the same input and output impedance.

if you start spreading these coils, you change the inductance, and hence, the characteristics of the halfwave filter. no longer will you have the same input and output impedances.
this impedance mismatch causes the filter to not be able to do its job very well, and this means that harmonics are showing up in the output.

we all know that wattmeters are dumb and just add these harmonics together with the fundamental signal freq.

this is why you might see an increase on your wattmeter when you spread these coils.
the increased harmonics are showing up as increased output power, but that power is not on 27mhz and does not help you get out one bit!

it can also wreak havoc when you hook up a linear that expects to see only 27mhz signals coming into it.

so, bottom line is, shops do this whether they know better or not.
they know that their customers just want to see more on the wattmeter, and spreading coils can give you that.

LC
Robb likes this.
__________________
https://i.chzbgr.com/maxW500/1912864512/h0491035C/

Reply With Quote
  #7  
Old 03-15-2010, 12:06 AM
BOOTY MONSTER
Guest
 
Posts: n/a
Default

a 2 pill amp would have a whole lot more effect and shouldnt be difficult on most vehicles charging system . sometimes some pretty good deals come up here in the for sale section .

................im just saying ......

Reply With Quote
  #8  
Old 04-22-2010, 11:41 PM
Switch Kit's Avatar
Senior Member
iTrader: (14)
 
Join Date: Apr 2005
Posts: 3,537
Switch Kit is an unknown quantity at this point
Default

you can set VR13 (SSB ALC) for about 15 watts if you want, but there really is no need. ??????

Just wondering why only 15 watts or less on this dual Mosfet radio ? Maybe I missed something here ?

Reply With Quote
Reply

Bookmarks
Worldwide Radio Forum



Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Suggestions on who to tune my Galaxy 98VHP BooDaddy Export Radios 123 04-17-2012 01:03 AM
Who to tune or not to tune my new Galaxy radio? PsRumors CB Band and CB Radios 66 11-24-2010 07:22 PM
New Galaxy DX2547 with IRF520 Mosfet finals movrider CB Radio Modifications 6 12-18-2009 08:59 AM
Galaxy DX 93/99 vs. 959 Skyhawk General CB Services Discussion 5 12-04-2009 02:16 AM
Galaxy DX929 MOSFET version and the RFX75 loosecannon CB Radio Modifications 3 07-26-2009 02:25 PM


All times are GMT -7. The time now is 10:02 PM.


Powered by vBulletin®
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.0
Worldwide Radio Forum