THX203 circuit not working

Hi

I have given connections as per the circuit, but i don't get output. Few components were not available, so i used some equivalent components. (SR3100 not available so i used MUR4100).

Only thing i did not use is the UU9.8 & DR6*8 inductor.

Will this affect my output? Is it definitely necessary?

Your schematic appears to be a flyback converter. Everything has to be right if it is to work. Questions:

* What voltage do you get across C1?

* The datasheet states power supply spec as low voltage (9V or 16V, it's ambiguous). What voltage (Vcc) do you measure at pin 2?

* The IC receives its power supply from a winding on the transformer. This appears to be a case of unreliable startup, since the primary winding needs at least a cycle or two of On-Off switching, so that other windings generate voltage. Although the datasheet explains how the startup stage works, everything needs to be right in order for it to work.

* Can you confirm the IC is switching the primary on and off? Is the frequency within device specs? Is it within transformer specc?

* Did you try putting a full diode bridge on the secondary? Then observe which pair of diodes carries major current? This should tell you which diode to leave in the circuit.

Hi,

I assume the problem is not in the schematic. I rather assume it is in YOUR circuit.
I don´t check your alternative parts datasheets. I assume you already have checked them and found out that they are compatible.

! ! ! ! ! !

Safety first!

You know you have a circuit where all the circuit contains dangerous voltage.
For further tests I recommend to use an isolating tranformer at the input.

It really is dangerous. High voltage may hurt or kill you and / or others.

If you don´t have an isolating transformer, then stop reading here.

! ! ! ! ! !

I assume non of the users has a remote scope or DVM connectred to your circuit ;-)
Therefore you should measure some signals and tell us the results.

* all with respect to DC input signal GND = "-" connection of C1
* Voltage at C1: DVM, DC voltage
* Voltage at IC1, Pin2: DVM, DC voltage
* Voltage at IC1, Pin1: DVM, DC voltage
* Voltage at IC1, Pin8: Scope, DC

Then we will decide what the next steps will be...

Klaus

let me prepare another board and let you guys know as the one i used blasted near the transformer area.