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Galaxy 949/959 varicap diode swap?

ExitThirteen

ExitThirteen

Grumpy and Cranky
Apr 18, 2008
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Cornpatch of Iowa
OK folks, I think I am going to do some experimenting. Seeing as the Galaxy 949/959's are so drifty, I'm going to do a swap of the varicap diode to see if I can increase the stability a little. I did some research and it seems that Galaxy is using a really cheap varicap diode, and I have a good pull from an old 23 CH. SSB radio. I'm planning on swapping in the new diode and doing a realignment and go from there.

Which brings me to my next question. Might anyone have a 949 or 959 they'd be willing to sell reasonable? I only want the radio, no power cord, bracket, or microphone is needed. It can be s transistor version or a MOSFET version. Cosmetics don't matter, as long as the radio is functional. Let me know if you have something that would work. Thanks in advance!


~Cheers~
 
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wish i had a radio to sell you to try this.

i hadnt considered changing the varactor diode, but ive thought for a long time about trying better quality crystals in that chassis.

i just havent had the gumption to get some made yet.

ill be sandbagging here waiting to see what you find!
LC
 
That would be cool as I want to look in to a 959 for my car but living up north temps swing a lot
 
I think there's something to be said about swapping varicap diodes. What I think is happening is that the varicap diodes in the 949/959's are thermally tracking, much like a diode that's used for biasing an amplifier... only difference is that the diode in the amp adjusts voltage or current, the varicap diode is changing capacitance which would cause the drift issue. So that's why I have reason to believe that changing out the varicap diode in the 949/959's with one of a higher quality (and also raising it up off the PCB) would help with this issue. If I can get a radio to try this on, I'll post the results.

LC, I have changed out the crystals in the past on the 949/959's, but no dice, the radios still drift the same despite the crystal change.


~Cheers~
 
If/when you get that radio, I will try to duplicate what you do on the 959 I have here.

Perhaps some wax on it might help neutralize some of the drift too?

What part do you have in mind?

I have a small assortment of NTE varicaps over here.
 
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I had a galaxy 88 years ago and changed the crystals out with some special made ones from international crystal and no luck doing that. even changed a few caps and no help. what I did with mine when was checking drift would warm it up and check the freq then put it in the freezer and the freq would change drastically from ice cold to warm. at least that is the way I checked mine for temp change and it worked great.
 
All one has to do in the circuit adjoining the varicap is touch a part and then watch it go waaaay off freq.

The real test for success is a shorter warm-up time, not being more than 120hz off freq at startup, and overall temperature stability - IMO. 148's are only off by 50-60hz at startup in a controlled climate - if that much. The 959 is usually off by +/-300hz in my radio room.
 
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Robb said:
All one has to do in the circuit adjoining the varicap is touch a part and then watch it go waaaay off freq.

The real test for success is a shorter warm-up time, not being more than 120hz off freq at startup, and overall temperature stability - IMO. 148's are only off by 50-60hz at startup in a controlled climate - if that much. The 959 is usually off by +/-300hz in my radio room.
Click to expand...

stick it in a freezer to match cold weather and you will be amazed how much it can be off.
 

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