NEC Px42VM3A lost all display

[Dblueman]

Re: NEC Px42VM3A lost all display

there's a label next to the PSU (Power Supply Unit) on the left. But not on the PSU itself but on the let call it the sheet which the PSU is attached too. This has 4 gold screws which hold it in. on that label is the following
42NH-PDP-4
S/N 02214262
Input AC 100-240v 50Hz/60Hz 5.4A
Output +170V 1.6A,+60V 1.6A, +5V, 4.0A,+5V,0.8A, + 3.3V 1.8A
+ 7V 0.5A,+13V 1.0A,+24V 1.25A +6V 0.15A
MFR. Origin Electric Co., LTD
Made in Japan

No other labels are on or near this PSU I looked under the PSU just to be sure.

[tom66]

Re: NEC Px42VM3A lost all display

So the PSU should supply 60V but it isn't, 60V is one of the voltages we need. Can you get a pic of underneath the PSU so I can trace where it might come from?

[Dblueman]

Re: NEC Px42VM3A lost all display

hope these will help. Let me know what I can do to assisit.

[tom66]

Re: NEC Px42VM3A lost all display

I'm going to take a stab that the last two rows are VA, because it makes sense based on the connector layout.

Those two black diodes -- check those. With TV unplugged & board removed, test on diode mode between pins 1-2 and 2-3, both ways. (Pins labelled arbitrarily from left to right, order unimportant.)

[Dblueman]

Re: NEC Px42VM3A lost all display

can you show me which ones and do I need to remove them from the circuit board

[Dblueman]

Re: NEC Px42VM3A lost all display

If I am correct the diodes are as follows 1 is behind the 4 white lets call them blocksnext to the heat sink and the other one is by a lone hwite box to the right of the 1500 uf 200V cap. Each of these reads 755 and 770

[tom66]

Re: NEC Px42VM3A lost all display

I mean the two lone black devices in this pic.
https://www.badcaps.net/forum/attach...7&d=1359412997

[Dblueman]

Re: NEC Px42VM3A lost all display

RC2 which has 3 pins reads 608 and RC1 which reads 678

[tom66]

Re: NEC Px42VM3A lost all display

Both ways?

[Dblueman]

Re: NEC Px42VM3A lost all display

what do you mean by both ways?

[tom66]

Re: NEC Px42VM3A lost all display

When you reverse the probes is the reading the same or different?

[Dblueman]

Re: NEC Px42VM3A lost all display

if you mean on RC1 which has 2 pins putting + lead on left and - on right and then switching them putting + on right and -on left it reads as follows
677 switching them it reads 547
as for RC2 which has 3 pins putting + lead on left and - on right it reads as follows
606 (+ on pin 1 and - on pin2) (+ on pin 2 and - on pin3) reads 1
(+ on pin3 and - on pin2) reads 606 ( + on pin2 and - on pin1) reads 1

[tom66]

Re: NEC Px42VM3A lost all display

They may be OK, but is it possible to remove them from the circuit and test them?

If those diodes are good, we need to find out why the VA transformer is not being driven.

[Dblueman]

Re: NEC Px42VM3A lost all display

RC1 the diode with 2 pins taken out of circuit board reads as follows
+ on left - on right reads 1
+ on right - on left reads 616

RC2 the diode with 3 pins taken out of the circuit board reads as follows
+ on left pin 1 - on pin 2 reads 171
+ on left pin 2 - on pin 3 reads 1
+ on pin 3 - on pin 2 reads 164
+ on pin 2 - on pin 1 reads 1

[tom66]

Re: NEC Px42VM3A lost all display

The diodes are fine then, re-install them.

[Dblueman]

Re: NEC Px42VM3A lost all display

okay sounds good.

[tom66]

Re: NEC Px42VM3A lost all display

Are there any fuses other than the ones near the main input?

[Dblueman]

Re: NEC Px42VM3A lost all display

no, just those two

[tom66]

Re: NEC Px42VM3A lost all display

Any like this?
http://www.jprelec.co.uk/image/624-035_big.jpg

[Dblueman]

Re: NEC Px42VM3A lost all display

nothing with that marking on the top. All I see is something simular that has 4R7 (there are 2 of these) and 1 that says 2R2