Repairing an RF602 receiver

cowasaki

cowasaki

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Darren
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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

RF602_01.jpg



Now the transistors (NPN type BC337)


RF602_02.jpg



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

RF602_03.jpg


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



You can now see the insides of the RF602 receiver

RF602_04.jpg
 
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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.

RF602_05.jpg




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:

RF602_06.jpg



Then use heat shrink tubing to cover the bare metal

RF602_07.jpg



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

RF602_08.jpg



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

RF602_09.jpg
 
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This is a snippet from the data sheet of the surface mount transistor that you cut off:

RF602_12.jpg



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

RF602_13.jpg
 
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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

RF602_11.jpg



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.

RF602_10.jpg
 
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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.... :) (y)
 
DekHog said:
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.... :) (y)
Click to expand...

Thanks, at least it was there in case anyone needed it! :)
 
Thanks for this... I'm staying away from HV flashguns so hopefully I won't need it... but if I do it's nice to know :D
 
i registered just to thank you for this clear repair description..
 
relfed said:
i registered just to thank you for this clear repair description..
Click to expand...

You're welcome. Glad to see someone found it useful.

Now you're here stay around for a bit and enjoy the place. There is a lot of really useful information on here :D
 
Hello! This is a very useful thread. I was wondering if the OP or anyone else has the schematics of the whole receiver, or of just the output stage for that matter? What was the original transistor? I am trying to determine why RF-602s have issues with Travelite strobes. I had a shoot in a studio with 4 of those today and only one worked with RF-602. However, I have checked the voltage (15V) and polarity on all four and found no difference between working and non-working units. All four work fine with the
PocketWizard.
Also, why are there 3 pins on the cable connector? I thought only two were used, but from the photos it seems that all 3 are connected...

Thanks.
 
There are 3 pins because the RF602 has two positions and pressing the button half way activates FOCUS but then pressing it fully activates TRIGGER.

You mention Travelite strobes and give their voltage as 15 volts. Have YOU measured this or looked it up?
 
cowasaki said:
There are 3 pins because the RF602 has two positions and pressing the button half way activates FOCUS but then pressing it fully activates TRIGGER.
Click to expand...

Hmm... I see...

You mention Travelite strobes and give their voltage as 15 volts. Have YOU measured this or looked it up?
Click to expand...
Yes, I have measured the voltage myself. It is something like 14.7V.
 
just now saw this - could come in handy sometimes.........

myself and slimbert have found that one of the main problems with the receivers is that the hotshoe connection is Plastic and does tend to break easily if a gust of wind blows things over!
 
mbmsv said:
Hmm... I see...


Yes, I have measured the voltage myself. It is something like 14.7V.
Click to expand...

Well thats why it isn't working then....

The RF602 is only designed to work at 6V maximum anything more than 6V and it starts to behave very erratically and anything more than about 12-18V and the transistor pops. You have been lucky not to have broken it :)

There is a way to sort this but it basically means a bit of work. You can use the output of the RF602 to drive an optocouple which is quite simple.
 
Have just opened up mine. The board seems to be the same as shown in the photos, but some parts are different/missing. E.g. in my unit the resistor in the base of Q2 is 560 Ohm (marking 561), and the zero Ohm resistor in the collector path is not installed. Maybe it is Nikon vs. Canon difference. Mine is supposedly for Nikon.
 
Lynton said:
just now saw this - could come in handy sometimes.........

myself and slimbert have found that one of the main problems with the receivers is that the hotshoe connection is Plastic and does tend to break easily if a gust of wind blows things over!
Click to expand...

Have you got some broken ones then?
 
cowasaki said:
Well thats why it isn't working then....

The RF602 is only designed to work at 6V maximum anything more than 6V and it starts to behave very erratically and anything more than about 12-18V and the transistor pops. You have been lucky not to have broken it :).
Click to expand...

Is it anywhere in the spec? I haven't seen this... Also, if I can figure out their output stage I should be able to modify it for higher voltage. Unfortunately it is not easy to extract the board fully to see what's on the other side. It's held in place by ho shoe solder joints.

In your mod you are connecting collector of the transistor directly to the black wire. In my unit I am measuring about 100 Ohm from the black wire to the collector of the original transistor...
 
I think it is not a transistor actually but rather an SCR. The marking on the part is 97A6 and I believe it's an SCR, which in theory might be able to keep 400V... In that case I believe a similar circuit was used in PT-04M triggers.
 
mbmsv said:
Is it anywhere in the spec? I haven't seen this... Also, if I can figure out their output stage I should be able to modify it for higher voltage. Unfortunately it is not easy to extract the board fully to see what's on the other side. It's held in place by ho shoe solder joints.

In your mod you are connecting collector of the transistor directly to the black wire. In my unit I am measuring about 100 Ohm from the black wire to the collector of the original transistor...
Click to expand...

I wouldn't bother to be honest.....

Get an RF602 to 3.5mm cable off ebay (if you don't already have one).

1 of 3xAA battery holder
1 of 4pin opto-couple
1 of 220ohm resistor
1 of 3.5mm socket (pin1 = tip)
1 of 3.5mm plug (pin1 = tip)

Connect pins as follows:

+ve of battery pack to pin1 of 3.5mm socket
pin2 of 3.5mm socket to pin 1 of opto-couple
-ve of battery pack to one side of 220ohm resistor
other side of 220ohm resistor to pin 2 of opto-couple

Right so basically you are connecting the output of the battery pack across the opto-couple input through a resistor and using the 3.5mm socket as a switch (switched by plugging the RF602 output lead's 3.5mm plug into it).

Now for the output connect:

pin 1 of the 3.5mm plug to pin 3 of the opto-couple
pin 2 of the 3.5mm plug to pin 4 of the opto-couple

Now when the Rf602 fires it will complete the circuit on the input side of the optocouple allowing the battery packs 4.5/5v to go through the opto-couple via the resistor. This will light the internal LED in the optocouple causing the output pins to short i.e. pins 3 & 4 which are now connected to another 3.5mm plug. You can now connect a flash of unto maybe 45 volts

This effectively does for about £1 what you pay £40 for one of them weinsafe things.
 
mbmsv said:
I think it is not a transistor actually but rather an SCR. The marking on the part is 97A6 and I believe it's an SCR, which in theory might be able to keep 400V... In that case I believe a similar circuit was used in PT-04M triggers.
Click to expand...

No it is a transistor and it is only specced for 6v as in my first post. I wouldn't bother messing I would just build an outboard opto-couple circuit.
 
cowasaki said:
No it is a transistor and it is only specced for 6v as in my first post.
Click to expand...

Yours is marked differently compared to mine. If you want I can post a picture. Do you know what the exact part number is? 6V transistors are rare. I don't understand why anyone would put a 6V transistor in such a circuit...

cowasaki said:
I wouldn't bother messing I would just build an outboard opto-couple circuit.
Click to expand...

If I were to build it I would rather build it inside of RF-602 as to avoid additional battery pack.
 
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mbmsv said:
Yours is marked differently compared to mine. If you want I can post a picture. Do you know what the exact part number is? 6V transistors are rare. I don't understand why anyone would put a 6V transistor in such a circuit...



If I were to build it I would rather build it inside of RF-602 as to avoid additional battery pack.
Click to expand...

The warranty and spec specifically state a maximum of 6 volts. To be honest it isn't really an issue for me as I use Lencarta studio lights, Lencarta safari lights and Nikon SB900/600 so all fit well inside the 6v.

Fitting the circuitry inside the RF602 in order to work with unto 50v should be doable. You could use a SCR or an opto couple but it is going to be a bit tight.
 
I am now pretty sure that Yongnuo is quietly changing the design and that my units in fact do have SCRs in them and not the transistors. There is a confirmation to this in a detailed discussion of these receivers on a Russian language forum here: http://impulsite.flybb.ru/topic170.html. For those who want to the schematic it is available there as well.
The problem I experienced probably has to do with the missing RC circuit which is required when a SCR is used.
 
Hi, like relfed, I registered just to thank for this thread. It was great I've repaired two RF-602 Rx, I've seen the russian foro and I think that they are proposing the use of a triac or scr.
Another thing, first I've solder the collector to the collector smd pad but it didn't work, there was no conductivity from collector smd pad to the black wire pad, something in the middle blown, maybe the famous 100 ohms resistor, so finally I've connected like you've done.
Thanks
 
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