Panasonic TV-P55ST30 loud pop, display black and 14 blinks

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, so I disconnected the SC board. I also disconnected the ribbon between the SD and SU boards.

I then took resistance readings on the two boards:

SD Board
Vfg on SD42 to pin 2 (Vscn_f) was 17k
Vfg on SD42 to pin 6 (Vfsv) was about 8 ohms (not k-ohms)
Vfg on SD42 to pin 1 (Vfo) was about 10k

SU Board
Vfg on SU41 to Vfo was 10k
Vfg on SU41 to Vscn_f was 17k
Vfg on SU41 to Vfsv was about 0 ohms

I took these things several times but again, not sure if I'm doing something wrong.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, so I disconnected the SC board. I also disconnected the ribbon between the SD and SU boards.

I then took resistance readings on the two boards:

SD Board
Vfg on SD42 to pin 2 (Vscn_f) was 17k
Vfg on SD42 to pin 6 (Vfsv) was about 8 ohms (not k-ohms)
Vfg on SD42 to pin 1 (Vfo) was about 10k

SU Board
Vfg on SU41 to Vfo was 10k
Vfg on SU41 to Vscn_f was 17k
Vfg on SU41 to Vfsv was about 0 ohms

I took these things several times but again, not sure if I'm doing something wrong.

yeah, had a feeling this would be a challenge. I'm not going to trust those results, could simply be the meter , try reversing the probes. At least there is some consistency between the 2 boards.

Try setting to continuity and do again, the VF5V if those readings are right should beep since it suggests a short but I think this could be a cheap meter.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, I used my analog meter to check continuity and all points beeped.

I used my digital meter and found the following readings. All readings were on 20M setting.

SD
Vfg to Vscnf off scale (reads as 1 .)
Vfg to Vfsv 2.9
Vfg to Vfo 14.2

SU
Vfg to Vfo 14.8
Vfg to Vscnf off scale like above
Vfg to Vfsv 3

Also, is there some way to check the SC board since it is removed/isolated to make sure?

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, I used my analog meter to check continuity and all points beeped.

I used my digital meter and found the following readings. All readings were on 20M setting.

SD
Vfg to Vscnf off scale (reads as 1 .)
Vfg to Vfsv 2.9
Vfg to Vfo 14.2

SU
Vfg to Vfo 14.8
Vfg to Vscnf off scale like above
Vfg to Vfsv 3

Also, is there some way to check the SC board since it is removed/isolated to make sure?

you've already proved the SC as bad, isolating and retesting is not going to prove anymore.

Don't know what the go is with the analog but seems to be a nuisance.

This is typical readings on a 2010 board but would be similar

VFO
2.2M

VSCN-F (TPSC1)
221K

5V_F
5.7M

Does the digital have a continuity or diode mode / beeper?

Try Vscn-f first again and set meter to the closest range to 221 K ohms and measure.

What options are there in the Megohm ranges?

I'm leaning towards these being ok if Vfo is not shorted and if 5v-F is in megohms.

I just want to see if we can get a value though that is close to what it should be.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Digital has a diode mode but no buzzer. Ranges are 200k 2M and 20M. I'll go check to see if I get a different reading.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Vscnf reads off scale on 20M. I tried in 2M but it over ranged.
VFO reads 14 on 20M range.
V5_f reads 3 on 20M range.

[Nick's Tvs]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Tnmg
When I first started I had the cheapest meter you could buy from Ace hardware and some of the functions like the beeper stopped working, so to confirm my shorts, I went into diode mode and got a 0.00 volt reading if the line was shorted or O.L if it was not shorted. It won't help with resistance however.
If you could post a picture of your meter or at least give the model of your meter it would help understand why you are getting all these crazy readings.
good luck

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Sure. The digital is a Sperry DM-350a. The analog is a radio shack meter. I'll post some pics this afternoon. The meters may be fine, it's probably user error

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

meters play a part in it. See how you go with nick's suggestion in diode but keep in mind this is an active cct so when in resistance the polarity of the probes can give different results so you could try blk on Vfg and then try red on Vfg but if you can be certain Vfo to gnd is not short and in megohms I think luck will be on your side.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

How can I tell if Vfo is shorts to ground or not? That's where my inexperience keeps coming back. If it is shorted to ground, how can I see that on my multimeter? I understand how to check resistance but don't know how to do this. If something is shorted to ground, will the resistance go to zero? It should buzz on continuity since it's a direct path to ground?

And for resistance checks and ground checks, does it matter which probe I land on the two points?

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

In diode mode, none of the points read zero. Half or over ranged others stabilize around 1.05 or .98. I'll post a pic when I can.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

In diode mode, none of the points read zero. Half or over ranged others stabilize around 1.05 or .98. I'll post a pic when I can.

I'd say it's not shorted then

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

So the SC is bad, SD and SU are good. Do I need to check all the buffers?

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

I replaced the SC board. Still getting seven blinks. Any other ideas?

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

all i can suggest is todo the sc50 jumper, buffer bypass test. disconnect the sd/su from the sc. remove the 4 ground bolts on the sd/su (vfg).

short the 2 pins together at sc50. turn the tv on and see if it still 7 blinks