TR-696FD-1 ERF2030 final kit problem...

[Robb]

Hi Y'all:

Put a dual-final kit in the TR-696.
I used a pair of IRF520N's instead of the ERF2030's; I was assured that they are the same piece and are completely interchangeable.
Problem is - I get 1/2 watt dead key and it swings to four watts.
I'm sure others have encountered this problem - but I thought I'd better ask rather than break something or screw something up.
Radio recieves fine - but transmits weakly.
What have I done wrong?
What haven't I adjusted correctly?
Should I have used the ERF2030's?
This should be an easy one for the tech guys...

 

[dudmuck]

did you follow the instructions?
http://cbtricks.com/miscellaneous/f.../galaxy_dx949_959_2547_erf2030_mod_rev1-2.pdf

There is an added 330pF to C201/C202.

The impedance matching around L31 is most likely whats up.
Check for correct procedure followed, then minor tweaking might improve.

 

[Robb]

Since I am new to doing mods, I would have thought that it needs a bias adjustment. Part of installing the finals was removing a fixed choke at L33; as bipolar transistors need it and MOSFETS don't. This particular board version came with a single bipolar 2SC1969 final. I followed the instructiions and checked my work three times or more.

 

[Robb]

I put it all back to stock w/the stock final and other assorted parts, and it works fine once again.
I even tried the kit as a single final upgrade - and it still didn't work.
The parts must be bad, so I am going to check each transistor and the bias chip for go/no go with my multitester.

I know it wasn't my work, as I put all of the stock parts back in correctly and it works just fine.
Its back to normal.

I've done other mods to this radio successfully. I've put a recieve kit in it and it works very, very well. I recommend it if you haven't done it before; the benfits are worth the small risks. Just take your time and check your work as you are going. I also put in the AF amp and the power amp with success as well. I kept those mods in. I also bought three mini-toggles switches for the frequency conversion and adding the roger beep.

But the dual-final mod kit is junk!

 

[Robb]

Hey Dudmuck:

Yes; I checked all of my work very thoroughly and included the 330pf cap as well. I turned every possibility many times over. Can't say for sure what is the reason - except that there probably isn't enough voltage to kick both of the mosfet's on. There is no low AM power pot on the board at VR18; it had a fixed 470 ohm resistor where that pot should be. I gave up on it, as I even tried a single ERF2030 mod with no joy.

Addendum:

The guy who sold me the kit is refunding me.
Apparently, not all of the TR-696FD-1's use the same circuitry and won't work with the kit. The 'Texxcomm' guy said that he has sold 100's of these kits - and no one had a problem until now.
All I know is that I re-installed the original parts and it is now working fine. I guess if I want to throw a bit more power out of this radio I will need to buy a small linear amp. I was hoping to get 50 watts out of this radio with the Wilson 1000 and the D104/M2. But I guess I will have to go with a 50-100 watt amp. I didn't want to run too much power, as I will need to have a laptop in the vehicle with me while storm chasing. Too much power will mess with the laptop; that is why I was trying to keep the power output within a manageable range.

Oh - well...

 

[formulamojo]

There was the old board designed for the 1969 final and the new board designed for mosfet finals...

Try the RFX75...