How to measure PFC (Startup) Voltage?

[topfli8979]

What is the correct way to measure PFC voltage, I have a Hitachi Plasma Im gonna start trouble shooting.

[tom66]

Re: How to measure PFC (Startup) Voltage?

Across the large 450V capacitors.
Note - PFC voltage is different voltage from the startup capacitors voltage often found around PFC ICs.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

+ probe top of cap, - probe to ground? Forgive my ignorance, not trying to spark 450v.

[tom66]

Re: How to measure PFC (Startup) Voltage?

across cap, so red probe on positive and black probe on negative, you do not want to probe relative to ground as that is a meaningless reading.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

How do you test it in circuit, tv powered up? I get no reading across these large caps.

[budm]

Re: How to measure PFC (Startup) Voltage?

Are you sure those are main filter caps for the PFC Voltage booster circuit?

[selldoor]

Re: How to measure PFC (Startup) Voltage?

How do you test it in circuit, tv powered up? I get no reading across these large caps.

testing in circuit is what you have just done?
You did have the set switched on ?
What is the model number of the set
Post a good picture of the board straight on.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

I figured that is what he meant about "across the cap" being in circuit. Set does not power up fully, goes into protection after about 6 seconds. I get NO voltage through out the power up process on my meter. Model # P60x901

[tom66]

Re: How to measure PFC (Startup) Voltage?

Those are the VSUS caps for the sustain voltage, I think.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

From what I can find on the interweb, the sub power supply is on left, main on right.

[tom66]

Re: How to measure PFC (Startup) Voltage?

To me, it looks like the sub PSU generates the PFC voltage, so you could try probing across that black/white cable running between the two.

[budm]

Re: How to measure PFC (Startup) Voltage?

Verify if the Black wire does go to the Positive leg of the cap and the White wire does go to the Negative leg of the caps, otherwise it can be HOT (Black) and Neutral (White) for primary side of the circuits.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

Verified black wire is ground, 380 v steady at the black/white plug. Caps to the right of plug are still not showing anything on the meter.

[tom66]

Re: How to measure PFC (Startup) Voltage?

That reading sounds about right. What's the actual fault with the unit?

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

Power tv up, fans/boards come on for about 4 seconds, goes into protection. Flashing blue led on front, no prime on the screen. Main supply has a high pitched sound coming from it.

[tom66]

Re: How to measure PFC (Startup) Voltage?

Count the blue blinks, error code should be in service manual.

[topfli8979]

Re: How to measure PFC (Startup) Voltage?

Yep, already did that,according to manual xsus bad. I have disconnected everyboard only way I can get it to fully power up and stay running is to disconnect c613 plug from main digital to power supply. Main board is good though, tried it another tv, operates as it should. I assume if xsus was bad, the tv would power up with out shutting down with the x disconnected.

[tom66]

Re: How to measure PFC (Startup) Voltage?

You assumed wrongly... sorry, this is a Hitachi, and they are terrible for repairability!
If a Hitachi plasma has an XSUS fault it will also give an XSUS fault with the board pulled. Great way to confuse.
You will probably find a bad FET on the XSUS.