ss cx4000 direct injection - almost there !

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Joined: Fri Aug 04, 2017 9:57 am

ss cx4000 direct injection - almost there !

Postby eddie14 » Fri Aug 04, 2017 12:00 pm

Hello !

I am very new here, very pleased to make a first post. I am tinkering with an old superstar ss cx4000, rather uncommon it seems ... ( )
It is pretty similar to a superstar 3900 , so I presume it would be not too hard to transpose.

Thanks to a lot of reading here and there, I could manage to direct inject audio , so I wanted to say a big thanks to all those who shared information about this, and share my little cent too.

The board is a EPT-3600-14b very similar to the Galaxy DX77 : ... h_main.pdf

Injecting at c191 works nicely for AM :
c191-am.jpg (29.32 KiB) Viewed 370 times

I removed c191, and injected through a 4.7UF capacitor to the junction of the negative end of C99 and the collector of TR21, with the + end of the capacitor soldered towards R238 and R239 ( the hole the most to the center of the board ). This works nicely and clean.

But I also wanted SSB so after a lot of trial and error, I ended with something working :

Many many thanks to Goldfinger for the precious hint here :

c191-ssb.jpg (71.4 KiB) Viewed 370 times

I left c125 in place, and soldered the + leg of a 10 uF capacitor towards pin1 of an612 ( IC3 ) , R260 and TR31, and inject the signal on the negative side of the capacitor. Working good ! :D
Removing c125 didn't work at all.

In both cases, AM in c191, SSB in c125, the audio negative goes to the board ground.

So far is works nicely with a dummy load, but as soon as I connect the real antenna and transmit, ssb sends an ugly carrier and the signal is lost in that big mountain....
I presume this is because of all the unshielded cables between the rig and the pc, and also because the radio is still upside down with internals in the open air...

I'll try to put this all together nicely and tight and keep you updated.

Thx for the great help guys, cheers
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Re: ss cx4000 direct injection - almost there !

Postby Goldfinger » Sun Aug 06, 2017 8:51 am

Let us know if putting the radio back together and shielding the cable fixed the problem.
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Re: ss cx4000 direct injection - almost there !

Postby eddie14 » Tue Aug 08, 2017 8:46 am

I will for sure !

I ordered various little things to put it all together, waiting for the postman to deliver...


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