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Galaxy 959 De-butcher/Modify (help appreciated)

U

UxCow

Member
Jan 3, 2014
22
4
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My second thread on here (and the first has garnered no response as of yet).

So I was gifted a 959 that was "done up." IE: blue lights, extra channels, echo board, and dual finals.

One big problem; this thing originally pushed a max of 10 watts out of 2xIRF520N. It was readjusted to make 20 watts...so I assumed something isn't right.

My background: I have spent some time (about 15 years) working on guitar and amp repairs (primarily tube). I don't have an oscilloscope or signal generator currently, but I have a decent DVM.

That said, here are some things I've noticed:

1.HORRID solder jobs; broken joints, solder balls, splatters, cold joints, no tinned wires for the mod board add-ins. I spent a good hour just fixing that.

2. A replaced power MOSFET, but only 60 watt. I replaced that with a 100 watt version.

3. Stock audio amp. Replaced with an upgrade.

4. L31 on the board was pretty mangled/erratically wrapped. Looks like an 8 turn with one wind going under the rest...does not look stock.

5. With so much solder, one of the finals had the drain shorted to the source. I'm going to assume if it wasn't burnt out, that was probably the issue.

6. All that really happened was a jumper was run for the drain of the extra final, and a capacitor in C212 spot.

7. No VR11 for second final biasing.

8. D90 looks to be replaced, but facing the wrong way vs. the diagram I've found online, and no D91 is in place for the second final.

9. L33 (resistor with a bead core) was removed, and replaced with just a resistor on the underside.

10. What looks like a PPE resistor/diode mod in shrink-wrap. This radio came from Rolling Radio from what I gathered (I am not the least impressed).

11. A tantalum capacitor on the underside linking other caps topside. Since it's in the signal path for the finals, I'm having to ask why someone would use Tantalum for that.

The goal: since this is my first foray into CB mods, I'm hoping to get this thing back to semi-stock (remove PPE and tantalum cap) and continue on with (actually) making it dual finals. The downside is no O-scope or signal generator to really test it. Hopefully I can find a local tech with these things to help me out.

While I am grateful for the gift (seriously cool to start out with this), I am rather unhappy with the lack of quality work from a radio modification business. I'm by no means a radio guy, although I've had my fair share of discussions about amp design and building (mostly tube) for high gain guitars.

This is kind of a work in progress/complaint page for me, but I'd love any meaningful suggestions. If you people want pictures, just ask, although I don't have much of the before pictures.


The "Too long didn't read, or TLDR" section:

I was given a modified 959 that is rather horked/butchered, and would love some pointers, as it has a few issues.

Thanks for reading.

~Cow
 

on D90 and D91 when you use a mosfet you reverse the direction of the diode from the bipolar schematic. maybe that is why it is reversed. also a 5.1 volt .5 watt zenor is the best to use.
 
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sonoma said:
on D90 and D91 when you use a mosfet you reverse the direction of the diode from the bipolar schematic. maybe that is why it is reversed. also a 5.1 volt .5 watt zenor is the best to use.
Click to expand...

Something I hadn't considered. Thanks. Perhaps this radio was a non-fet version? Looks like a Zener is in place on the right-hand one (looking at radio component side up, front of radio facing me), and stripe is on the left. The left FET has just a jumper running to drain (center leg), and I de-soldered the source leg from the drain.

I really just need to post pictures on this thing, and hopefully will tonight.

I don't mind the challenge of learning this, and having it run properly, but will say it's a touch annoying that someone would even put this out as a finished product (not Galaxy, but Rolling Radios).

Yes, I am fond of lengthy, verbose responses.
 
L31 is a weird looking coil from the factory. the way you describe it seems about right.

if it has been spread out in an attempt to increase power, it should be put back to normal or replaced.

you should definitely put it back to stock singel final status, as the dual mosfet mod for the 959 type radios is not the easiest to do, and it sounds like someone got almost all the way done and realized they did something wrong and gave up.

follow the schematics on cbtricks.com and you can get that radio back up and running.
LC
 
I was wondering if you'd reply, LooseCannon, since you made a thread on going dual final with the radio.If I'm right, I have the backbone of the radio ready (better power supply and audio amp), and adding in some parts is not an issue to me; only tweaking them properly is the real challenge.

I was thinking it may be more work going back to stock than simply finishing up the work. I managed to mostly put L31 back to stock shape, minus some very slightly imperfect coils. It looked like a pig's tail when I first got the thing.

I'll be perusing over the schematic for the next few days to determine 100% what was done to this thing, and probably remove some of it (still eying the PPE and tantalum cap mods). Hopefully tonight I can take/post some pictures to give more meaning to what I'm saying.

Hopefully I'm not :bdh:
 
Finally took some pictures. I tried focusing mostly on the finals area, but took a few extras for good measure.

One other thing I forgot to mention: the thermal "paste" I found under the heatsink was really Vaseline, and the heatsink didn't even touch the chassis, except for the edges. Probably had 1/32" gap, or slightly more.

couldn't upload here, so sent them to a photo site. If the picture is too small on that site, just click on it, and it goes full screen.













 
I'm used to seeing the clear mica insulators for MOSFETS (at least in high current amplifiers). I can imagine how the ceramics might offer the capacitance needed for radio use. The downside is they will not transfer heat all that well due to thickness.

Now to find some ceramic insulator pads.

It looks like the pads under the FETs are made of "frag tape," or heat transfer tape. Whether or not that insulates enough is another question entirely, but certainly won't address the capacitance issue.

If only they used mica...I have plenty of those around.

One question: are ceramic screw insulators also required for this? I have nylon around, but zero ceramics, and they seem to be rather tough to find online as well (I have no real suppliers here that I know of).
 
Last edited:
Where did you buy this radio? Was it an E-Bay special or from a cb shop? New used? Reason I say is if it still works sell it on e-bay. 959 radio's are a dime a dozen, why not order one done right the first time and then be done. As an example this guy is the best I know with 959's, he does some wild things. That or get a new one with a factory tune/alignment.

Custom CB radios
 

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