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Galaxy 959 De-butcher/Modify (help appreciated)

Mongoose said:
Hey Cow, these work pretty good, more than enough for what you need or you make one from a thick film resistor too.
Salt Water Dummy Load
Click to expand...

Thanks, Mongoose. Just call me "Cannoli." :p

I'll see about getting an So-239 female connector and pretty sure I have the rest of the stuff around. Of course, I probably have some high power bathtub resistors, but not sure if they'd hold that kind of power.
 
UxCow said:
Thanks, Mongoose. Just call me "Cannoli." :p

I'll see about getting an So-239 female connector and pretty sure I have the rest of the stuff around. Of course, I probably have some high power bathtub resistors, but not sure if they'd hold that kind of power.
Click to expand...

You might consider going down to the hardware store and buying two items. A one-gallon paint can/lid (~$2) and a gallon of clear mineral oil (~$16). Mount your SO-239 on the top/center of the lid and mount your 50 ohm load resistor to the base of the SO-239 so it fits down in the can. Fill the can with enough oil to submerge the load resistor in the can; but not so much to cause it overflow when sealing the can. This will allow for a 50 ohm/50 watt resistor to handle 10x as much as power. A 100 watt resistor will handle 1000 watts, 20 watt will handle 200 watts; and so on. Of course, there is is still a half-minute or less duty cycle near the upper limit; but cheap, solid, and efficient.
 
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I've dealt with mineral-oil submersed things before; resistors, transformers, and whole PC components.

I'll probably get 1 or 2 Caddock resistors, as I have plenty of heatsink material, water blocks, and other cooling bits left over from building custom water-cooled PCs (using a dual pump, triple radiator one to type this).

The salt-water one is pretty cheap, too, with only the cost of the plug, and finding some solid core copper wire (Romex, anyone?). Lots of options here. Just wish I had the time to build the thing, although the film resistor would be more portable. I could even get a couple 100-ohm MP930s, put in parallel and have the 50 ohm load, with 60 watt capability. Math is fun, sometimes :p
 
After quite some time of not having the time, I finally managed to test this thing out using a salt-water dummy load.

Thought it was doing better than it was at first, then realized I was tired and mis-read the meter.

I'm wondering if my meter may be defective, as I can get no SWR reading at all. Can't zero it, or anything. However, the built in SWR meter says I'm....sitting at a 1:1. Doesn't move.

Biased the MOSFETs out to 3.6 (VR12) and 3.5 (VR10) volts. Echo board and additional channels were left in.

variable power down, it will deadkey at 2 watts. Variable up, it will do about 4-4.5 watts deadkey. That is the limit of the trim pot, and it won't go any more.

Modulation goes off the meter's scale, and adjusting VR16 has very little effect. This is using the stock Galaxy mic it came with.

The external watt meter is showing about 12 watts max output.

Looks like it's back to stock for output, but with the upgraded components in place. Now...to seek more wattage from it. I'm open to suggestions.
 
UxCow said:
After quite some time of not having the time, I finally managed to test this thing out using a salt-water dummy load.



I'm wondering if my meter may be defective, as I can get no SWR reading at all. Can't zero it, or anything. However, the built in SWR meter says I'm....sitting at a 1:1. Doesn't move.



Modulation goes off the meter's scale, and adjusting VR16 has very little effect. This is using the stock Galaxy mic it came with.

The external watt meter is showing about 12 watts max output.

Looks like it's back to stock for output, but with the upgraded components in place. Now...to seek more wattage from it. I'm open to suggestions.
Click to expand...
when using a dummyload you wont /shouldnt see any swr ,its suppose to be a 50 ohm load
so id say you built a good one. as for vr16 recheck your modulation limiters robb listed
a couple pages back cause disabling these WILL cause this. also look for any other swing mod and disable them. as for extra power id either put on a rfx75 or buy a klv mobile amp
 
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Peaking the four transmit coils (L40, L42, L43, L44) in SSB mode with a 1khz audio tone (http://www.freesound.org/people/klangfabrik/sounds/28636/) fed into the mic with a watt meter and dummy load will peak the output; but adjust the bias voltage on the driver/final first. Forget about messing with the receive alignment; you just don't have the necessary tools for that (SINAD meter, sig gen w/variable & calibrated output = expensive!). But if you have a freq counter, dummy load, watt meter, and a DVM, you should be able to get the rest of the radio aligned fairly close.
Galaxy Radios DX959 Service Manual
 
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Robb said:
Peaking the four transmit coils (L40, L42, L43, L44) in SSB mode with a 1khz audio tone (Freesound.org - "TONE 1 kHz 44.1 16bit.wav" by klangfabrik) fed into the mic with a watt meter and dummy load will peak the output; but adjust the bias voltage on the driver/final first. Forget about messing with the receive alignment; you just don't have the necessary tools for that (SINAD meter, sig gen w/variable & calibrated output = expensive!). But if you have a freq counter, dummy load, watt meter, and a DVM, you should be able to get the rest of the radio aligned fairly close.
Galaxy Radios DX959 Service Manual
Click to expand...

Once upon a time I had a tube-based O-scope, and signal generator...but that was 15+ years ago.

I'll try adjusting, although I currently have the driver and final biased according to instructions I've seen. I also found some other instructions, and decided to check this radio to see if it was performed.

Instructions were:
Remove C218 (3pf) and discard. - (Yep, it's missing)

Change C216 (470pf) to a 1000pf (100V mylar-type) - More like 680 pf ceramic disc type.

Remove C210 (470pf) and discard. Has a 2a152j (1500pf 100V) film cap

Remove C199 (560pf) and reinstall it in the C210 spot. (Yeah, it's empty, too)

I'm wondering if these are affecting it in a bad way.

Q39 was left alone, with no resistor in line, so I'm guessing I need to look elsewhere in the circuit to see what was done to boost mod so high.

Also, I'll point out that my power supply for this is 12V, and not the standard 13.8, so I'm expecting that to lower the output a bit, and possibly might mess with my bias as well, as I've seen that happen in guitar amps.

Another curiosity I've noticed; the dimmer pretty much kills the freq. counter when it's lowered a bit, but the channel counter and meter light dim properly. I may need to look into the dimming circuit and see what exactly was done.

This is still quite the learning process....but thanks for all the help, peoples...it's most appreciated.


UPDATE: Tried adjusting L40, 42, 43, and 44 in SSB. Watt meter reads around 10 watts or so with 1KHZ signal input. Internal meter reads a little higher.

Tried it on AM side, getting 2 watt DK on low RF output, and 4.75 on high, and the radio swings out to about 12 watts on the external meter, showing about 14 on the internal.

I biased the driver and final a little hotter (around 3.8) and didn't notice any issues. Modulation is great so far, but the RF output is still pretty weak. Not sure if I've done something wrong, or if there is some other mystery to this thing that's preventing it from pushing more watts. All in all, the L adjustments gave me approximately 2 more watts.

Not sure where to go at this point, or other areas to look at to improve output.
 
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i just messed with my 2950 and its showing lower output numbers too15-20 watts on ssb
ROBB what would happen if he tunes the L coile 40-44 for max carrier in am mode
as his output is low anyway.also try 14 volts but keep it under 15 volts. mines set at
14.3 same as my van w/ engine running
 
hotrod said:
i just messed with my 2950 and its showing lower output numbers too15-20 watts on ssb
ROBB what would happen if he tunes the L coile 40-44 for max carrier in am mode
as his output is low anyway.also try 14 volts but keep it under 15 volts. mines set at
14.3 same as my van w/ engine running
Click to expand...

AM carrier has its own VR controls in the 2950.
When the TX coils are peaked in SSB mode, this also affects AM peaks too.
So don't worry about it.

The manual says to use 13.8v to align radios; 14v isn't that much different.
However, 15v is just too much.

Make sure the driver/final has the bias is set FIRST.
Best to do as the Service Manual says and use USB mode for peaking - for best results.
Then set the SSB low and hi power levels; then AM low and hi power settings.
BTW - DO NOT touch L34 or VC3!

http://www.cbtricks.com/radios/rci/rci_2950/rci2950_tx_adj.htm
 
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Tried it out in car, with it running, so getting the standard 14.5, and 14 under Xmit load.

Bias was at 3.76 for driver/final. Still biased a bit hot, but should be OK.

Output did, however, creep upward a bit. External meter is showing 18-20 watts on AM, and internal is showing 20-22 with a good "aaahhhh" into the mic (still stock Galaxy mic with mod pot and mic gain cranked).

It's pretty close to where I want it, just wish it had more output, but what I'm hearing on talkback isn't back. Time to hook up a real antenna and see who's out there, I suppose.

At any rate, its output watts are no less than they were before, with the half-baked dual final setup it was running. At least I know some things were put right in the radio.

Thanks for all the help everyone! Now I need to go drill a hole in my car's roof and install the Wilson.
 
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