Vestel 17PW01-4 PS board stuck in standby

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

Does Pin 5 at switch on reach 12V. If not then check R501. If VCC does not reach 12V at switch on then the IC will fail to drive the transformer which provides the secondary VCC for that IC to sustain operation.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

If that's pin5 on IC806, it gets to 237V on a Fluke 85 in DC mode. The trace is below:



VCC on pin 2 reveals the same trace.

R501 measures 10K

[R_J]

Re: Vestel 17PW01-4 PS board stuck in standby

IC806 VCC is Pin number 2, be sure to use hot ground when checking voltages inthe primary. I suspect you are using chassis ground for your scope, this will not work for checking signals in the primary. and DO NOT connect your scope ground to the hot ground without an isolation transformer or you will damage the power supply board

All your scope is measuring is the 50Hz potential between one side of the a/c line and earth ground.

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

+10
Use your multimeter set to DC volts to check if (VST) Pin 5 reaches 12V or not at switch on.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

The board is connected to mains via an isolation transformer, the scope is not. is that correct?

My ground for the scope is PL846 in the center of the board, it's also joined (with crock clips) to PL814. In normal use, both these points are joined to the metal chassis of the TV.

Looking a the schematic, I am unsure of the difference between these two grounds:



IC806 pin 5 measures 239V DC withe board powered. If I bridge PL816 pins 6 to 16 Pin 5 is essentially the same at 240V DC

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

Using the ground reference mentioned above PL846 & PL814. If I measure DC Pin 2 on IC806 i get the following:

4.83V 6-16 unbridged
The fluke is jumping around and unable to give a reading when 6-16 is bridged.

[R_J]

Re: Vestel 17PW01-4 PS board stuck in standby

A is hot ground, B is chassis ground. If the power supply is connected to a line isolation transformer, you should be able to connect the scope ground to the hot ground.
The two points are NOT connected together

USE HOT GROUND when checking voltages etc. in the PRIMARY !! PL846 and PL814 are CHASSIS GROUND in the SECONDARY

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

Hi All,

Are there any further thoughts on this?

Many thanks.

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

What is the maximum dc voltage at switch on using your multimeter between Pin 1 (GND) and Pin 5 (VSTR) of IC806.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

350v dc.

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

Now what is the maximum dc voltage at switch on using your multimeter between Pin 1 (GND) and Pin 2 (VCC) of IC806.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

7.4v dc

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

That voltage is too low to kick start IC806. From the data sheet for FSDL321. Read Pin2 and Pin 5 function.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

the 10K R501 measures 10K. D896 shows a voltage drop of 0.5V.

where does the +400V supply come from on the anode side of D896?

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

Generated by NCP1653, (IC830)

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

I think I found it. Is it at the right hand side of all those caps (962-963 et al)?

To the left of them is L867 which has a low resistance, so I guess is OK(?)

To the left of that is D110 which is difficult to measure in circuit as it's under a soldered in heat sink. With the meter in diode mode i'm measuring: a drop of 0.354v.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

EDIT!!

Regarding IC860:

VCC to GND = 15V DC

GND to DRV = 0V

GND to CS = 0.03v

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

If Vcc (Pin 2) to Gnd (Pin 1) is 15V then the IC should be operating.
However GND to DRV should have measured close to 400V dc since DRV is connected through the transformer winding pin 5 and out at Pin 6 to the 400V supply line. You can consider the transformer winding to be just a lenght of wire in this case connecting the two points together.

[Nevillet]

Re: Vestel 17PW01-4 PS board stuck in standby

On IC806 (FSDL321) I measure the following DC voltages:

1 - GND
2 - Vcc 7.4v
3 - Vfb 0.542v
4 - Ipk 0.005v
5 - Vstr 350v
6 - Drain 3.8v
7 - Drain 34.1v
8 - Drain 18v


On IC830 (NCP1653) I measure the following DC voltages:

1 - FB/SD 1.923v (when probed, creates some HF noise somewhere on the LV side)
2 - Vcont 0.223v (when probed, creates some HF noise somewhere on the LV side)
3 - In 4.92v
4 - CS 0.002v
5 - Vm 2.932v
6 - GND 0v
7 - Drv 0.000v
8 - Vcc 15.00v

[dick_barton]

Re: Vestel 17PW01-4 PS board stuck in standby

One of your diodes supplying +12V is in backwards.