STRS6707 via S6709

Thread Starter


Joined Apr 2, 2009
Any one familiar with this component.
I got the data, so no need for that.
It's just that this is a SMPS offline Regulator used in TV's and has a lotta demand.. here...still...I must say.

OK, Why I am asking all this is just my curiosity or may be the thirst for knowledge.

You see, I had lotta these for say more than 5 years. I got them from Lanka. I bought them my self u know, but I never got to replace them here in main land.
But it all got used up in a snap during my recent trip to the northern island.
In fact I ran short, which is the main reason for this thread.

Pls look at the data for reference.

Problem comes due to counterfeit component scams. There too I got a problem with a fake BUK11(philips Hout) transistor. The bloody thing blew faster than I can blink. So I decided to take the matters to my level, which I dare not say much abt.
NeverthelessHere I go, so, not being able to trust what I bought from Male' before the trip, I decided to do do what I am talking about.

First of all take a look at the data sheet. On the second page you will find the functional block diagram of the Reg I am talking abt.

See the Power switch at pins, 1,2 & 3. The power transistor pins.
As far as I can think and even today I find these Reg's faulting by shorting that Tr in number of ways of which a Power transistor would fail.

And I was able to adapt a way on testing them, A quick Series element test method and I duuno who else here (in Maldives) has acclaimed that this method was done by that individual. Cause as far as U know, I was teaching and used to tell the students that you can be sure tht the power transistor inside the STR is not faulty by a standard diode check.
This was something I learned my self.

So based on that I tried another approach to the faulty STR's that I had then in Hoarafushi. What I really did not know is that I was going to do something that as far as I know, no one has done, in an island in which the people a famous thru out Maldives for their ingenuity during the old days.
Which I am shocked to say, Made in "Hoarafushi".

Ask me about the story later in off topic.
As for the STR, what I did was tht I took a dead STR and an old Sony TV PCB. Sawed out the PSU Area and fixed all the components back into the supply with a dead STR.
As far as I know, this supply can run without the actual load.
It has an error amp at the out put which provides feedback via opto to regulate the desired voltage.

Which I must say it pretty nifty. All I need is to change the error amp number to change the +B Voltage. Quite simple and effective.
OK. Now with a dead STR in the circuit I cut the base and collector pins.

Found a horizontal output transistor, wired it up and mounted it on the same heat sink with the STR and soldered the B,C,E to the board respectively.

Only difference in that the power transistor is out side. kekekeke :D

The guy next to me took shelter while I powered it up.
Heck ! I never blinked once. It started up in the first time. Just the start up squeak and was up and running. I used an 8A Ic one with a S6707.
I figured it should handle the load..

Man !! I am good, I made history..Made in Hoarafushi...:p.

Just a little bump. :D

Why the heck does it take 6 squeeeeeks and around 5 seconds before it starts up and stabilizes when the actual TV's loads are connected ?

I mean without the TV it just fires up A-OK first time, but with TV, it would.. Squeeeek, Squeeeek, Squeeeek, Squeeeek, Squeeeek, Squeeeek,and then I get a steady picture and all the rest.

Supply is stable and runs at nominal temps.

It worked but with squeeeks.

So......any one dare to high light the main problem.



Joined Sep 21, 2010
Just a thaught, the horz o/p transistor your using has it got an internal diode from C to E ? This may be upsetting it, try a transistor designed for SMPS & see how it goes. Like your Idea, that IC is $18 Trade here .

Thread Starter


Joined Apr 2, 2009
I am way a head of u, I did thought of that, but why would a suppression diode effect start up.
Give me some time to post a schema.
The Original PSU has a diode that mounted like the damper across C E.
eeeeep! I forgot. Does dampening effect the start up
Here is the PSU schema. The A board area is Supply


Last edited:


Joined Sep 21, 2010
I dont see any diode across C/E in the circuit only across B/E. I would still try a Transistor with out internal diode at least asgood as orig spec Ic6A, Vce850V. Why do these fail? is it the electrolytic C614, 220uf 25v drying out? Lucky to see a CRT TV here these days they are all LCD or plasma, since digital transmission started most people changed there TVs.

Thread Starter


Joined Apr 2, 2009
U are right about the caps failing.
I had to change both caps to prevent the new ones failing.

Funny ... I sometimes find one diode shorted. Which is reverse biased to C and GND.
Lemme check a PCB.