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DX959 - Unknown/understood mod

T

tinkerer973WI

W9WDX Amateur Radio Club Member
Jul 12, 2008
26
0
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Well, long story short for now, Been asked to do some work on a friends DX959, mods are simple enough, but I always inspect, run, and document everything I find before I actually do any work. I believe this is a newer MOSFET model, and most of the mods/repairs I'm finding make sense. there are 2 I'm wondering about though, maybe someone can shed some light on them for me. The first is a pair of surface mount components one is a diode, the other is unknown. The diode parallels D16, the unknown parallels D17. I'm thinking either a botched Schottkey type upgrade or some other rx improvement. The other mod is a 2sc945 emitter to collector of Q55(2sa1869) and 945 base to Q55 emitter, Center leg (945 collector) is clipped off. Again, anyone know what these are doing?

Thanks Tinkerer973wi
 

Just a bump, really can't make sense of the diodes D16 and D17 being paralleled , or the extra 2sc945 on Q55 in the AF power circuit:censored:. Probably going to pull them out and try to fix the traces they cut to isolate the ground trace they couldn't solder around, unless someone has a clue to a valid reason for leaving them in there.

Thanks
 
have no idea what the mods are for. just looked at the schematic and D16 and D17 is the 1st diodes in the receive. not sure what they were trying to do. did they leave the originals still soldered in place. the trans has to be a out put mod maybe for swing.
 
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my apologies, I said they were paralleled and the are not, the originals are gone, just can't under stand why they wouldn't put whatever the parts on the solder side are back on the top, less they don't want anyone knowing what they put in? or can't get it except as a surface mount?
 
tinkerer973WI said:
my apologies, I said they were paralleled and the are not, the originals are gone, just can't under stand why they wouldn't put whatever the parts on the solder side are back on the top, less they don't want anyone knowing what they put in? or can't get it except as a surface mount?
Click to expand...


are you saying the diodes they put on the bottom are surface mount components? the 2 factory ones are oddball from what I saw on the schematic, so that may be what they did. something like a 1ss53 or something like that. did not go back and look. those factory ones can be blown if the radio gets hit by some one up close and maybe using power. if the receive works good leave them there. just not sure what the trans mod is. has to be some form of swing mod. I even called my buddy that has been in the repair business for over 40 years and he has not seen the trans mod. he has seen a lot of radio actives super wac pac mods and has removed them to get the radio working right. that was why I called him on this one. did you look at R264 to see if they had put a diode on the right side of the resister for a swing mod. also did they leave the trans in place for the modulation limiter. think it is about Q39. the link robb left you from Defpom's sight will have it listed.
 
This wouldn't happen to be a "Factory Reconditioned" model would it?

If SO, I wouldn't change a thing... I've seen Galaxy do some really weird stuff to their Factory Recons that I couldn't figure out via the schematics or factory service manuals.

If it is NOT a factory recon, then yes, by all means, put it back to Factory Stock, and then just realign it and do the standard AMC/ALC increases accordingly. That's really ALL these radios need.
 
These radios benefit the most when the transmit coils are peaked - IMO.
Set the gate voltages on the driver & final.
Then set the modulation level up on a scope.
That should do it . . . ;)

I agree with Sonoma, D16 & 17 are not the locations for the schottky diodes.
D30 & D31 are; and D1 & D2 are the noise blanker.
 
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Well the trans mod is some sort of swing mod, definitely helped AM swing. Radio wasn't originally running, but who ever was in it last bent the brackets for the shorting bar feeding the output stage, no contact no power. Radio seems like it runs pretty good , needs an alignment , but otherwise performance is good, going to check the receive later, D16 and 17 are suppose to be 1SS53's, RF parts has them as do a few other places I checked, don't know why they changed them, but I hope they work with the shottkey upgrade.

As for a Fact. Recon. I don't know buddy got in on Ebay, betting that will be the last he buys from there, he's %&^ pis23d. At least it's up and running.

I'm no pro by any means, and learning is half the fun.... and most of the cost;), but that's why some of us do it.....

Thanks to all who chimed in,

Tinkerer973wi 73
 
tinkerer973WI said:
Well the trans mod is some sort of swing mod, definitely helped AM swing. Radio wasn't originally running, but who ever was in it last bent the brackets for the shorting bar feeding the output stage, no contact no power. Radio seems like it runs pretty good , needs an alignment , but otherwise performance is good, going to check the receive later, D16 and 17 are suppose to be 1SS53's, RF parts has them as do a few other places I checked, don't know why they changed them, but I hope they work with the shottkey upgrade.

As for a Fact. Recon. I don't know buddy got in on Ebay, betting that will be the last he buys from there, he's %&^ pis23d. At least it's up and running.

I'm no pro by any means, and learning is half the fun.... and most of the cost;), but that's why some of us do it.....

Thanks to all who chimed in,

Tinkerer973wi 73
Click to expand...


D16 abd D17 are not the ones you mod for schotsky diodes like Robb told you. you said there was some bent pins on the mirror board contacts. did you look to see if there was a wire running to the middle pin? if so they bent the middle pins to take the 6 volts or so off the board and did the version of the npc/rc mod.
 
Sorry to leave any everyone hanging, the surface mount components at D16 & 17 are factory, they can't keep stock of the typical 1ss53 so they grind the traces and used SM parts. All the twisted 4148's are also factory same concept, can't keep stock of the original parts. No wires from the test point, that was my first thoughts when I saw the hardware bent, but nothing there. Otherwise all seems good as of right now. audio is running about 95%. Seem to run kinda hot after I motor mouth on it for a while, is this normal, I always thought MOSFETs ran cooler than conventional outputs....I'm getting about 35 PEP SSB and 5 DK with about 12 avg swing AM. Am I pushing this thing TOO far....?

Thanks
 
Well, it's still alive but I don't think it would have lasted long either, thus my question. Yup single Mosfet radio, seem to run and sound good NEW problem, been trying to reset the biases and the Service manual is for Bipolar outputs, says 50mA and 100mA resptivly, driver and final, well, driver bias (VR12) won't go below 170 mA, final I can get to 100mA no problem. I did find R246 is 10 ohms not 5.6 like the schematic says, and r249 is a mini inductor with a resistor across it on the solder side, schm. says "core". My 959 has the 5.6 ohm and a ferrite bead on a wire at r249"core?" I cant seem to see any other differences and I tried swapping the inductor for the ferrite bead with very little effect on the bias. I'm figuring either a short to ground somewhere, or I've missed something else. but I'm sure pulling 3 times the current is probably why it's getting hot. By the way is it just me or are the tp 7,8,9 labels goofed up on the schematic? Thanks Tinkerer
 
The bias adjustments on the driver/final for the MOSFET radio aren't done the same way as the earlier bipolar transistor radio.

Put the '+' lead of your digital volt meter on the gate pin of the driver and the '-" lead to the board ground (not the chassis ground!), then set the meter on 'voltage'. Driver voltage should be set at ~3.5-4v. Do the same for the final. Set less than 4v and they should stay reasonably warm.

There is a resistor that feeds the gate of each MOSFET, you can trace it and see. It has a small white circle below it - printed on the board. You can put your '+' lead on the top lead of that resistor and that makes it easier to get your reading.
 
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Got it Robb, no problem there, part of the problem was VR12. change that out adjustments went well, all is good. Getting about 26 or so SSB and about 12 on the AM swing 5 watt DK. Now to get mine sounding better , got it used from a truck driver at work, said he didn't like it, AM sounds fine SSB tx is really "muddy " sounding, limiter is still in it, but I haven't looked it over real close yet, price was right, NEVER ARGUE WITH FREE!
 

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