cowasaki

Flash in the pan has been selling the rather wonderful little Yongnuo RF 602 transmitters and receivers for a while and wanting to do a bit of off camera flash I bought 2 pairs off him.

I used them with my SB flashes with no problems then blew both the receivers up trying to use them for two old flashes that I had with output voltages over 200v. They were never designed to take anything over 6V so that was my fault and I bought two more.

If you want to check the output voltage of a flash my thread about that is HERE.

Anyway I decided to have a look at one of them today and realised that the output transistor, which is the thing that get blown, is EASY to replace and did so. I thought you lot might find the exercise interesting and possibly useful so here we go.

WARNING

This thread is in relation to the replacement of the output transistor of the RF602 with the circuit board shown in the pictures. It will void all warranties and in fact your warranty is already void if you have blown your receiver in this way anyway.

To test that this is the fault make sure both your transmitter and receiver are on the same channel and slowly press the button on the transmitter. The light on the transmitter should go green then as you continue to press harder it will go red. If it just flashes red it is on the wrong channel!

This repair is done at your own risk


First the transmitter and receiver




Now the transistors (NPN type BC337)





First remove the batteries, battery cover then back case of the RF602 receiver



NOTE: 2 screws longer than the other go at the socket end



You can now see the insides of the RF602 receiver

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cowasaki

Now that we have the transmitter in pieces we can see the transistor that is faulty, it is the large oblong device to the right of the spring with "GND" next to it.





We can now prepare the transistor. Place a BC337 (NPN) transistor on the bench with the flat surface downwards and solder 3 wires to the transistor as can be seen in the diagram:




Then use heat shrink tubing to cover the bare metal




Now remove the faulty transister, I just used snips to cut it away.




This diagram shows the solder points. You could just use the original points BUT it is easier to use these points

cowasaki

This is a snippet from the data sheet of the surface mount transistor that you cut off:




And this is the equivalent from the data sheet of the BC337

cowasaki

We now need to connect the relevant wires to their locations inside the RF602 receiver:

Base

This is the hardest connection to make as it is going to the existing connection. Don't worry if it touches the nearest side of the component next to it as this is what the circuit board does anyway. With my transistor this is the BLACK wire.


Emitter

This is "2" on the surface mount component and on my wired up BC337 transistor it is the RED wire. This needs to be connected to GND and the easiest connection on the circuit board would be to connect it to the GND spring




Collector

This goes to the solder pad that the black wire can be see going to in the diagram (labelled "C"). My transister would be the YELLOW wire.

DekHog

Three months and not one reply to this, Darren?

Just to say good on you for going the extra mile and taking the pictures and writing the post - hopefully I'll never need it myself (No HV guns here anymore), but I'm sure someone might....

cowasaki

Thanks, at least it was there in case anyone needed it!