Magnavox 37MF321D/37 No Power, No LED. Testing a diode.

[budm]

Re: Magnavox 37MF321D/37 No Power, No LED. Testing a diode.

I am having a hard time tracing the copper trace on picture 1134, 1135. Is the resistor connected to C2083 positive leg then it goes some where else?

[johnboy1313]

Re: Magnavox 37MF321D/37 No Power, No LED. Testing a diode.

Yes, the resistor connects to what would be the + lead of cap 2083 if there was a cap there, and then to inductor 5080.

[budm]

Re: Magnavox 37MF321D/37 No Power, No LED. Testing a diode.

OK, now that is better pictures, thanks, and I can now see that the Anode of that 9.1V Zener is connected to pin 1 & 2 which are the +16VDC output pin, the Cathode is hooked up to the resistor, the output side of the resistor is connected to pin 3 which is the +24V pin.
So the voltage difference between +16V and the +24V is 8V, so at normal operation, that Zener will not conduct until the difference between the +16V and the +24v is higher than 9.1V, this can happen if the +24V is not fully loaded due to backlights inverter circuits is not on yet. When that unloaded +24V goes up higher 25V, the Zener will turn on and clamp down the +24V from going higher than 25V. So if that Zener is shorted or have low resistance the 24V will get pulled down toward +16V and also heat up the resistor.
So the 9.1V Zener is correct, I would get the 9.1V 1 Watt for the replacement.
What a differrent when I get to see good clear pictures. Now you understand why we need good clear pictures.
Bottom line, the power supply will work without the Zener but with less protection if output way over +24V and damage the inverter board..