whole new repair / learning world... plasma! Yikes!

**tom66** · 10-02-2018, 02:10 AM

Re: whole new repair / learning world... plasma! Yikes!

MID is across the two blue caps on the right of this image.
https://www.badcaps.net/forum/attach...6&d=1524904441

It's generally 80-120VDC, or half Vsus +/- 10%.

The green light should glow on the board if VMID is good.

If VMID is low then there is a good chance that your sustain output is not, uh, sustaining.

A scope is helpful at this point.

**budwich** · 10-02-2018, 06:22 AM

Re: whole new repair / learning world... plasma! Yikes!

thanks for the direction... in the posted image, those appear to be on an su/sd board as opposed to an SC board... is this the right read? Not sure I would notice a "green light" but maybe "any light"... I am color deficient... :-) Scope... not immediately available.

**tom66** · 10-02-2018, 06:27 AM

Re: whole new repair / learning world... plasma! Yikes!

It's on the SC. Post a pic of yours. That's an SN board which is equivalent to an SC + SU + SD board.

**budwich** · 10-02-2018, 06:48 AM

Re: whole new repair / learning world... plasma! Yikes!

Ok... You might even see my "less than wonderful" soldering / hack of the board. :-)

I see the two "big blues" that would be the equivalent of your image.

Based on your comment, I should see some voltage across either of those, measured on the DC scale.

Attached Files

**tom66** · 10-02-2018, 06:55 AM

Re: whole new repair / learning world... plasma! Yikes!

yep those are the ones, on the right. Should briefly tick up to 100V before shut down. If volts are low something is SUS..because it aint SUStaining...

**budwich** · 10-02-2018, 08:04 AM

Re: whole new repair / learning world... plasma! Yikes!

So with everything connected, I get a reading of 128vdc on the cap... with respect to the "ground array" just below the caps in the picture (note the "array" is not actually grounded to the chassis ground screws... ie no connection).

are you able to see the "green light led" on this board... nothing jumps out at me.

**tom66** · 10-02-2018, 08:27 AM

Re: whole new repair / learning world... plasma! Yikes!

That is on the high side.
Would need a scope to figure out what's going on right now, IMHO.
If you don't have that you're stuck just testing parts and looking for shorts, but could be something silly like a gate driver bad somewhere, which could take almost forever to track down.

**budwich** · 10-02-2018, 08:43 AM

Re: whole new repair / learning world... plasma! Yikes!

ok... I haven't used a scope in a long long time... I think I can get a "friendly loan" (unless I blow it up) of an old 2 channel scope. How safe is "playing" around in the area without any isolation transformer which I don't think I can get?

Having said that, the 2011 TS manual for 6 blinks indicate the MID circuit range is between 67 and 138... is this range of voltage for the reading that I found? Further, down in the same section of the TS, it indicates that the "6 code" could also be set by the failure in the Vscan generating circuit.

**tom66** · 10-02-2018, 08:48 AM

Re: whole new repair / learning world... plasma! Yikes!

Your MID voltage may be in range. I would expect closer to 100V once the set has started.

You don't need an isolation transformer for this work, in fact if anything it can create further danger.

It depends on how old the scope is.

Vscn can also be tested by finding the resistor it is across -- may also be able to find a schematic...

**budwich** · 10-02-2018, 09:07 AM

Re: whole new repair / learning world... plasma! Yikes!

ok... I will see about the scope... I know its an old Leader two channel.

I was looking at the block diagram in TS manual... It shows two paths for the SOS signal out of the SC to the A. One path comes from the SOS detect "box" that monitors the energy recovery circuit. The other path comes from the Vscan detect box. These are "added" via two diodes and sent out on a line to the A board. Maybe I can check with a meter which of these is high/low??? not sure which to see which circuit is actually complaining... IF I can figure out where those monitor circuits are.

this is the pdf page of the functional diagram.

Attached Files

tcpxxgt30.pdf (82.6 KB, 11 views)

**tom66** · 10-02-2018, 09:15 AM

Re: whole new repair / learning world... plasma! Yikes!

Yes you may be able to do that. A schematic helps - I believe the 30 series has schematics available...tw2005 may be able to advise if he is still around.

I know that the SOS6 for the MID voltage is generated by a comparator which also drives the LED, so if you see an LED on the board, small SMD device, then chances are that it's near there.

**budwich** · 10-02-2018, 10:08 AM

Re: whole new repair / learning world... plasma! Yikes!

I found a copy of the service manual for the tcp50s30. I think this page shows most of the diagrams. Note sure about the component numbers as I don't 16xxx on the board... maybe no 16 or there is a xref somewhere.

Attached Files

panasonic_tc-p50s30_sc circuit.pdf (230.5 KB, 9 views)

**budwich** · 10-02-2018, 10:46 AM

Re: whole new repair / learning world... plasma! Yikes!

based on the attached PDF of the sc board diagram, I found the LED for the MID. Wow, that's a very small LED. Anyways, it lights up for about 2-3 seconds when power on is depressed... then goes out. I guess that means that perhaps the MID is OK and shutdown turns it off.... maybe.

I will look at the "other leg" of the sos6 "trigger" lines.... there is a test point - tpsos6. Hopefully, I can monitor that point with a meter to see if it goes high.

**budwich** · 10-02-2018, 11:54 AM

Re: whole new repair / learning world... plasma! Yikes!

OK... tpsos06 is near the sc20 connector. At ac plug in (standby), with a relay click (entering standy), tpsos06 goes high... I guess while the A board initializes... maybe... but at about 10 sec. period, it is eventually low (0). Then with power on, it immediately goes high, a second or two later, the LED on the MID goes on... just when it goes on, tpsos06 goes low, some period thereafter (one to seconds), I think I see tpsos06 start to go high (meter reads 2.5 or so) and then shortly thereafter, the MID led goes out. Does this mean anything? Vscan error?

**budwich** · 10-02-2018, 01:51 PM

Re: whole new repair / learning world... plasma! Yikes!

I also see the led on the SS board light in sync with the led on the SC board.

In addition, I monitored the TPVAD, its goes to 81 then bounces to may 168 and then back down to zero with shut down. What should this voltage be? Stable at some level?

**budwich** · 10-02-2018, 07:12 PM

Re: whole new repair / learning world... plasma! Yikes!

I monitored tpsc1 during power on. It went to only about 30vdc, then shutdown. That doesn't seem right... but I don't know as I can't find any value in the TS manual. Tested that point for resistance which is one of the checks. It was high... in the Mohms.

**budwich** · 10-03-2018, 09:00 AM

Re: whole new repair / learning world... plasma! Yikes!

It looks like "metering" will only happen for now as the "friendly scope" needs the friend to get it going... it has been used in along while and not sure when or if it can happen.

Anyways, one fire at a time... :-)

continue to look at the voltages supplied thru out the SC board. Focused vscan area since it appears that leds on the SC / SS boards light for a bit along with a brief screen flash, so maybe the panel itself is getting "powered" and the cause of the shutdown / 6 blinks is maybe in the vscan circuit... guess.

From the SC diagram, I monitored the F15V (15v_f) that was supposed to coming out of IC795 going towards IC724 to provide 5v_f that goes to the SU/SD boards plus VH generator that ultimately goes to those boards. Measuring that "line" (supposed to be 15), it goes to -100Vdc ????? wrt to chassis ground. Something wrong either with the ground point reference... oops maybe I see now... "_f" which I take is "FLOATING". Where / what is the reference point for this measurement?

OK... I see the TPVFG... voltage floating ground... :-)

added: 15 volts checks out.

**budwich** · 10-03-2018, 10:37 AM

Re: whole new repair / learning world... plasma! Yikes!

since I noticed the "floating ground" lines in the diagram, I recheck the tpsc1 level which is a floating voltage. It reads 147vdc (floating). How and is this related to the MID voltage / range of 67-138???? Is this the issue?

Also rechecked TPVAD... its 200 vdc (floating).... not sure what the range on that is.

**budwich** · 10-03-2018, 11:21 AM

Re: whole new repair / learning world... plasma! Yikes!

so in summary, with power on and before shut down.

TPSC1: 147vdc (VscnF) Ts schematic indicates 147V +/-3
TPVAD: 200vdc TS schematic indicates 200V+/- 5
V15F: 14.95vdc
V5F: 4.95vdc
MID voltage: 128vdc (chassis ground) - Troubleshooting manual indicates range 67-138.

**tom66** · 10-03-2018, 11:31 AM

Re: whole new repair / learning world... plasma! Yikes!

Sounds like you have a TPVSCAN issue. Though I have seen other faults such as bad floating 15V cause a 6 blink code.

To check the VSCAN it should be tested between the TPSC1 and "FG" outputs. FG are the screws connecting the buffer and SC boards.

Expect around 150V for VSCAN. If it is low, and VAD is present, the likely cause is a shorted buffer IC.

whole new repair / learning world... plasma! Yikes!

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