Galaxy DX929 MOSFET version and the RFX75

[loosecannon]

hi all,

i just acquired a DX929 in pretty darn good shape for 10 bucks. (my best find of the year so far!)

it is the version that comes with MOSFETS from the factory.

i want to install an RFX75 unit in this radio, and i have a couple of questions.
if anyone has already done one of these radios successfully using the instructions on CBtricks; please chime in here and let me know if the instructions work like they are printed or did you have to change anything to make it work?

my main question has to do with VR10 and VR12. in the SSB versions of this board (basically the same as a 959 board with lots of parts missing), these VR's would be for the biasing of the driver (VR12) and the final (VR10).

if any of you go to cbtricks and look at the service manual, you will find that they are not addressed as an adjustment because the service manual is for the old version with the 1969 final in it.

in the schematic for the MOSFET version, they are indeed there, and do in fact seem to be the bias adjustments for the driver and final.
my radio does have them in it.

the problem is that the instructions on cbtricks for the MOSFET version of the 929 shows VR12 replaced with a fixed resistor (probably a 100K), and nothing for VR10.

in my radio, both VR10 and VR12 are paralleled with 100K resistors. R241 for VR10 and a 100K in place of C291 for VR12.

so, i think that the difference will matter when i go to install the RFX75 unit.

it seems like if i removed the VR's that my radio would be just like the figures in the install of the RFX75, but it seems to me like Galaxy wouldnt put them there if they werent needed.

so, anyone know anything about this?
done an install of the RFX75 in a MOSFET DX929?
do any of these ramblings make any sense to anyone? LOL

thanks for any help or advice anyone can lend.
LC

 

[Warbird]

No doubt a GREAT find for $10.

I am not familiar with the installation of the RFX75, but you are right VR10 and VR12 are there for biasing. MOSFETs like a little voltage on the gate hence the fixed value resistors in your 929, it helps with the dead key. Look at the service data on CBTricks for the MOSFET version of a sideband version of that board (959 or 2547). The sideband radios have VRs and not fixed value and I *think* you set the driver at 3.75 volts and the final(s) at 3.5 volts.

I hope that helps at least for the "why are they there" question.

 

[Chop]

is there something wrong with the mosfets in the radio? i ask because i wouldn't tear up a perfectly good radio to install a rfx75. my opinion, though.

 

[loosecannon]

ive got lots of radios, and i like to build them up for different purposes.
some are made to go with amps, some are made to put out as much as possible on their own, some have different freq ranges, etc...

this 929 was a really good deal, and its in good shape, so i figured it was a good candidate for a high powered radio that you can put in a car and stick a mag mount wilson on the roof and go for it without having to worry about a linear.

who knows, after im done upgrading it, i may just sell it. im sure there are plenty of truckdrivers who would like a powerful radio but cant run an export for whatever reason.


warbird, thanks for the info! we'll see what they are set at now.

later,
LC