VP2030b Power Supply Problem

[budm]

Re: VP2030b Power Supply Problem

Try heating up that startup cap with hair dryer to see if the power supply will start running again, capacitor ESR goes down when heated. If the MOSEFT shorted out, it can also take out the Gate drive circuit inside the IC plus any diode and resistors connected to the Gate of the MOSFET.

[retiredcaps]

Re: VP2030b Power Supply Problem

The 22uf capacitor hasn't been changed but appears to check out OK on the multimeter (it's reading 22uf across the terminals while in circuit).

The Fluke 185 is a fine multimeter, but no multimeter can measure ESR. If ESR is high, the circuit won't work.

[Rtech]

Re: VP2030b Power Supply Problem

If it is the IC 1 that is faulty, then don't buy one,I have 5 new ones and can easily put one in an envelope.They are also known as DAP8A as well as NCP1203,and they are supposedly used on Delta DAC boards 19M05,19M010.19M011,19M015,Acer1916Was,Va1912W,and surpising to me Xbox...I have a 19M010,and confirm it is used on that.The DAP08 according to ON semiconductors were made specifically for one Manufacturer and no Datsheet was made available.

[chrisuk]

Re: VP2030b Power Supply Problem

OK, I replaced the two capacitors in question with no change. I then removed IC1 and checked the voltage on the relevant pads and this time it was just a few millivolts. And now I think its time to come clean, ....before I found your forum during the initial stages of trying to find the problem I found two damaged diodes one blown apart and the other looked discoloured (I think, - its been a while ago now).

It was a zener diode (ZD4) connected underneath the pcb between the 0v and the negative of the large 150uF capacitor that was blown apart. I thought I identified it as being a 15v zener and so put one of these in its place.

I think I also replaced another zener diode (ZD3) connected on the top of the pcb connected between pin 1 of the 2SK3569 and the 0V again I thought I identified this as 15v.

I have a horrible feeling that you are all making a collective sigh and are about to tell me these are the wrong components.

Anyway, I mention this as I'm tracing the power supply to IC1 and it seems to be heading for these components and the MOSFET.

I await your advice.

Rtech, thanks for the offer of the DAP08. I may need one and I'm happy to pay for it.

[chrisuk]

Re: VP2030b Power Supply Problem

Correction to my previous information ;

The zener diode (ZD4) is connected underneath the pcb between the 0v and the junction between two resistors R7, R8 and an inductor L1 and not to the -ve of the large 150uF capacitor. Sorry for any confusion.