Sanwa Airtronics RD 6000 hardware problem

[H.J.]

Hi Helifreaks,
that's my first thread ever and above all in English. So please don't concentrate on my language mistakes, I have a much more interesting story for you: I bought a used T-Rex 450 V1 and when starting the setup, I recognized that my transmitter a Sanwa/Airtronics RD 6000 (1st edition) didn't work. The display looked O.K. but no transmission at all. After checking all possible failure roots I finally opened the housing and .... a transitor fell down on the floor! :confused: It doesn't look damaged.
I have never seen or heard about an electronic device that unsoldered itself!
Now I have the problem to refix it, but in which direction? So I want to ask those of you who own a Sanwa RD 6000 or RD 8000 to open it and have a look at the lower circuit board.
33882
On the picture of mine you see the empty place on the board which is marked with "Q4" and a white rectangle. One side of it is thicker than the others. Is that the marked side of the transistor or the unmarked? Maybe someone can take a picture of his board.
Thanks a lot.
H.J.

[papafoster]

H J Hi from Australia It will go back in the way it is on the photo, if you look at the print outline on the pc board you can see that it is off centre to the holes. Place the part back in so that when looking from above the part matches the printing on the pc board
When soldering it back in place the tip of the iron on the leg of the part first, then slide the iron down to touch the copper etching on the pc board and then apply a small amount of solder from the opposite side. Just make sure that you have a fine tip on your soldering iron and apply the heat only enough to make a solid joint.

The part was most likey not put in correctly from the factory, what they call a dry joint, and fell out over time with useage

Good Luck Allan

[H.J.]

Thanks Allan.
tomorrow, a friend of mine will test the transistor. If positive, I will go on as you recommended.
Let's see what will happen.

Greetings from snowy Germany
H.J.

[HeloMech]

another tip for ya:

if you're soldering iron tip is too large, you can coil some safety wire around it like you're making a spring, then leave a section pointing out and use that section as the new tip of your iron. Typically .040 works well for me.

[swales]

I can tell you EXACTLY what has happened.... as it just happened to me... Someone installed a transmitter battery pack with reverse polarity. Most manufactures put the Positive (Red) wire in the center of the 3 pin connector... but Airtronics puts it on the outside pin. If you connect a battery pack that is wired the other way it will cause the transistor at Q4 to de-solder itself. The radio may still work to see the menu's, but it will not transmit.

I was not sure if that was the only thing that could have been damaged, so I sent mine in for repair. They said it will cost between $20 and $40 to repair.

[H.J.]

To finish this story: I resoldered the transistor...nothing. Then I replaced another candidate on the board, a SMD voltage stabilizer and ... it worked! ... but only 5 minutes.
After an unsuccessful looking around in the net to get this damned transistor somewhere in Europe I bought a new transmitter from JR. Let's see if I can still use the Sanwa for my flight simulator.

[TMoore]

In the two months since the first post you could have sent the TX back to Sanwa, had them fix it and been flying it.

TM

[H.J.]

You're right TM (of course), I am not complaining but to be honest, I lost confidence in Sanwa. Futaba and JR using poka joke during their TX developments - means they design against faulty operations like I did. The battery connectors do not allow misusage.
Now beeing able to compare the RD6000 with the German version of the JR 7202 called Graupner MX16 I do not (at all) regret my decision to send the Sanwa into exile.
H.J.