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Galaxy DX-959 Mods - 10kc Switch Modification | Radioaficion Ham Radio

Galaxy DX-959 Mods - 10kc Switch Modification

Article Index
Galaxy DX-959 Mods
10kc Switch Modification
Clarifier (Unlock) Modification
Clarifier/Frequency Counter Realignment
Microphone Wiring Pinouts
Frequency Roadmap
All Pages

10kc Switch Modification:

*Note: As I verified (successfully) the following mod by performing it myself, I ran into some degree of difficulty -especially with cutting the trace as specified. This is a lot trickier than it sounds due to the placement, size, and proximity of the surrounding traces and solder points. I recommend exercising a great deal of care and by all means, TAKE YOUR TIME with this mod! Once you take a look at what you're up against you'll see what I mean. If you have shaky hands or even the slightest doubts, it would be wise to have someone else you trust perform the mod for you. It's just not worth messing up a neighboring trace and well, you know what that means...   :(

Here are the steps to perform this mod:

1 - Locate pin 16 of the MB8719 PLL chip.

2 - Cut the trace on pin 16 and place a 4.7K ohm quarter watt resistor.

3 - Next find a miniature SPDT three position, "center off" switch. You can get these at Radio Shack.

4 - Solder a wire from the center contact on the switch to the chip side of the resistor that you just placed across the cut of pin 16.

5 - Take another wire and solder it to one of the remaining contacts on the switch and run it to pin 18 of the PLL or DC ground.

6 - Solder a wire to the remaining switch contact and run this wire to pin 9 of PLL.

The center position is for normal channels. However, depending on the currently selected channel, the two switch positions will allow you to go to the channel immediately above or below thus allowing access to the desired "A" channel frequencies. See the
roadmap for the specifics on using this mod.

By popular demand, here are some pics of the channel & 10kc mods:

Galaxy DX-959 Mods

Galaxy DX-959 Mods

Galaxy DX-959 Mods

Galaxy DX-959 Mods

Galaxy DX-959 Mods

Galaxy DX-959 Mods

~Broad-banding the 959~
This mod is not recommended for the novice.

Greedy for more channels? Speaking for myself, I'm perfectly happy with the nice batch of new frequencies acquired in the P5/P6 mod above. After all, I really can't work with many more lower or higher frequencies without having to retune my antenna anyways. My match goes up significantly at both extremes as it is! But if you absolutely positively MUST tinker further, then read on...

Additional channels (with slight variation of coverage) can be made available which requires the use of SPDT switches instead of SPST switches. This also requires the attachment of the P7 control line to the switch so that the line coming from the PLL on the main board is switched between the original control line (P5 or P6) and P7.

Some people feel this mod is really more trouble than it's worth (and may be potentially dangerous) since the P5/P6 channel mod in the steps above safely provides more than enough extras. Ever compare it to the old Cobra 148 GTL channel mod? The Galaxy ends up with roughly the same extra frequencies!

Note: According to Galaxy, broad-banding (opening the PLL to it's fullest potential) the DX-959 simply requires the removal of diode "D3" on the VCO module. The earlier radios had this diode. If it is not there on yours, then you have the later model which already comes without it. Another alternative is to replace c296 with a .0015uf capacitor. Two different techs say either method will work -providing the VCO doesn't lock up... it's possible, but it shouldn't.  :o)

If anyone has already done this mod or has further related info and/or corrections, please e-mail me the details.

*I have not done this mod so don't hold me responsible if you try it and your radio blows up!  :o)

A Better Alternative: VIAGRA!!!
The new "Viagra" channel boards are a much safer and depending on the channels you want, a better way to go. These kits are readily available, rather simple to install, and you get 120 channels. However, as you can see below, the range differs from the P5 / P6 channel mod above.

P5 / P6 mod range: 26.695 to 27.965 
(Goes higher than the Viagra mod, but not as low)
~ 23 channels below and 49 above (112 channels total) ~

Viagra mod range: 26.515 to 27.855
(Goes lower than the P5 / P6 mod, but not as high)
~ 40 channels below and 40 above (120 channels total) ~

So basically, there are only 8 channels missing with the P5/P6 mod.