Dual output power supply 5 and 12 volts (no output)

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

hello, I have decided to replace all the components of the primary, I am waiting for them to arrive, I have not yet done the test with the power supply working for it is hermetically closed and for the moment I would like to avoid breaking it to open it, we will hear from you as soon as I have made this further test

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

so the resistance between the two pins I have to test it in ohms? the zener diode I had checked and it looks good, in any case tomorrow I replace it

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

I did the tests you asked me, between pins 5 and 8 I have 0,89 volts, the winding of the transformer that I tested without power is 0.01ohm

That's not what I asked. I said check the resistance between the pins not the voltage, I already no the voltage is .8v . If nothing is shorting pin 8 to ground, then the ic is bad and not producing the 5 volt reference.
It could be possible that zener diode connected to the vcc line is bad. It could check like a regular diode but be zenering at too low a voltage.
Since you have another power supply, compare the resistance of the ic pins to ground and see id there is a difference

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

I noticed a big mistake, the resistance marked on the photo, originally was 4.7Kohm and not 47ohm, could it affect?

That would likely not effect the ic's operation, it would cause a problem once the power supply started and would likely just blow the 47Ω resistor.

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

I noticed a big mistake, the resistance marked on the photo, originally was 4.7Kohm and not 47ohm, could it affect?

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

I wanted to tell you that I have another one working, could I do some tests?

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

It's all getting very strange, what could I see again?

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

I did the tests you asked me, between pins 5 and 8 I have 0,89 volts, the winding of the transformer that I tested without power is 0.01ohm

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

so in summary, I have to test if between pin 5 and pin 8 of the IC there are 5volts, I had already tested the optocoupler, I tested the output as a diode test, but it didn't mark anything, is it right or did I have to have some value? and then the transformer

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

Check the resistance of pin8 (ref) to pin5(ground) Pin 8 should have +5 volts if the ic is working, If the pin is not shorted or very low resistance to ground, check the output pins of the optocoupler to see if they are shorted. if not I suspect the ic is bad.
If you look at the datasheet you will see that the VCC pin supplies the 5v reference, so with 8.x volts on the vcc pin, the ref should be there as well.

Also check the winding of the transformer (marked in yellow) it should read less than 1Ω

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

yes there is an error I inverted the pins, working with the ic on the contrary I made a bit of a mess ...

Pin5=0
Pin6=0,03
Pin7=8,20
Pin8=0,87

others are right

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

forgive me I had left the tester set to test the big capacitor with the drain, here are the updated results

Pin1=0,47
Pin2=0,18
Pin3=0,35
Pin4=0,58
Pin5=0,87
Pin6=8,20
Pin7=0,03
Pin8=0

Your pin voltages are wrong. are you sure pin 6 has 8.2v and not pin7?

[R_J]

Re: Doppio alimentatore in uscita da 5 e 12 volt (nessuna uscita)

.

[falcontech]

Re: Doppio alimentatore in uscita da 5 e 12 volt (nessuna uscita)

What happened? Post #24 you had
Is the 220k that connects the 315 volts to pin7 of the ic bad? Is the diode that is mounted across the ic bad?

I can check, it's one of the ones I replaced first, I also check the diode but I had already done it and it was good

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

forgive me I had left the tester set to test the big capacitor with the drain, here are the updated results

Pin1=0,47
Pin2=0,18
Pin3=0,35
Pin4=0,58
Pin5=0,87
Pin6=8,20
Pin7=0,03
Pin8=0

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

voltage between capacitor and drain 315 volts
Pin1 = 0
Pin2 = 0
Pin3 = 0
Pin4 = 0
Pin5 = 0
Pin6 = 0.08
Pin7 = 0
Pin8 = 0

What happened? Post #24 you had

i've 8,2 volts, the capacitor is 47uf-35 volts

Is the 220k that connects the 315 volts to pin7 of the ic bad? Is the diode that is mounted across the ic bad?

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

voltage between capacitor and drain 315 volts
Pin1 = 0
Pin2 = 0
Pin3 = 0
Pin4 = 0
Pin5 = 0
Pin6 = 0.08
Pin7 = 0
Pin8 = 0

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

all clear, let's hope my hands don't shake , I'll do the test and let you know

When checking the ic voltages just follow the trace from the pin and check the voltage on the next closest component, that way there is less of a chance of shorting.

[falcontech]

Re: Dual output power supply 5 and 12 volts (no output)

all clear, let's hope my hands don't shake , I'll do the test and let you know

[R_J]

Re: Dual output power supply 5 and 12 volts (no output)

You can use the negative lead on the big capacitor for all the tests, that is what is called HOT ground.
Check that there is voltage on the drain of the mosfet (that is the center pin) be careful not to short to any other pin. the voltage on the drain should be around 325VDC
Then leave the negative probe on the cap negative and check EACH of the ic pins
Pin1=
pin2=
pin3=
pin4=
pin5=
pin6=
pin7=
pin8=