Having rebuilt a few and blown up a few, Ive come up with a possible cause.
Many ideas have been suggested over the last couple of years, usually relating to heatsinks and parts ratings etc...
It is known that some types made post 2010 the board mounting-screws cause the problem, working loose and allowing the earth/groundplanes to arc to chassis.
Here's my theory on 'em.
All Pan plasma sets that Ive seen have a Two Pin VSUS connection-leads set up from P (PSU) board to the SC/SN and to the SS boards.
This two pin comprises the VSUS Supply and a Ground return to PSU.
It therefore stands to reason the entire VSUS current passes through just the One 1 sq mm Pin of this connector. While (to my knowledge) there havent been any obvious burn-ups of these plugs/sockets--Why Not...?
--Because when they DO give issues--The SC Blows up instantly--and kills the set stone dead anyway, so there's no burn-up!
Ah--then Why doesn't it happen to earlier Panasonics then...?
There's one feature the later sets Don't have the earlier sets did.
--Lots of VSUS Decoupling-Caps on the SC or SS boards.--Sometimes as much as 1500uF worth of caps on each board....
These later sets have only a couple--Maybe 500uF of capacitance,--Not enough to prevent spiking issues in the case of a slight weakness of the connection on any of the four points the VSUS passes via these plugs....
So--The known issue of Ground Arcing--Admitted by Panasonic in the issuing of screw kits is one way these SC/SN die.
A single pin supplying the full VSUS supply arc could well do the same IMHO.
This is Exactly what happened to me this morning. The set, a 42C2B with rebuilt SN board running fine. While doing something unrelated to this set, I just brushed against the Cable Only leading from the SN to the P board, with my elbow.....
That was enough--2 blink, Q661, IC773, Q818 Q401, Q421 etc short--A typical SC/SN blow-up.....
The cable was the Original and had been refitted After all was well and I had removed my test-cable containing The Bulb.
This original lead had been unplugged when the set first came to me and then after all repairs etc done, had been refitted to the set.
My Test Cable--with The Bulb was made from an SC/P board cable from an older PZ70 set, and was quite firm on the plug pins.
The original to the repaired set was much looser in its fit to the pins of the board. Very careful examination of the board pins showed a VERY SLIGHT pitting in the form of a line across the supply pin--but no discolouration/black/burns. Fitting and removing the plug on the pins a few times, removed most of this...
So--Once its repaired (Again!) I'm gonna cut the bloody plugs off and solder the damned cables solid!
Many ideas have been suggested over the last couple of years, usually relating to heatsinks and parts ratings etc...
It is known that some types made post 2010 the board mounting-screws cause the problem, working loose and allowing the earth/groundplanes to arc to chassis.
Here's my theory on 'em.
All Pan plasma sets that Ive seen have a Two Pin VSUS connection-leads set up from P (PSU) board to the SC/SN and to the SS boards.
This two pin comprises the VSUS Supply and a Ground return to PSU.
It therefore stands to reason the entire VSUS current passes through just the One 1 sq mm Pin of this connector. While (to my knowledge) there havent been any obvious burn-ups of these plugs/sockets--Why Not...?
--Because when they DO give issues--The SC Blows up instantly--and kills the set stone dead anyway, so there's no burn-up!
Ah--then Why doesn't it happen to earlier Panasonics then...?
There's one feature the later sets Don't have the earlier sets did.
--Lots of VSUS Decoupling-Caps on the SC or SS boards.--Sometimes as much as 1500uF worth of caps on each board....
These later sets have only a couple--Maybe 500uF of capacitance,--Not enough to prevent spiking issues in the case of a slight weakness of the connection on any of the four points the VSUS passes via these plugs....
So--The known issue of Ground Arcing--Admitted by Panasonic in the issuing of screw kits is one way these SC/SN die.
A single pin supplying the full VSUS supply arc could well do the same IMHO.
This is Exactly what happened to me this morning. The set, a 42C2B with rebuilt SN board running fine. While doing something unrelated to this set, I just brushed against the Cable Only leading from the SN to the P board, with my elbow.....
That was enough--2 blink, Q661, IC773, Q818 Q401, Q421 etc short--A typical SC/SN blow-up.....
The cable was the Original and had been refitted After all was well and I had removed my test-cable containing The Bulb.
This original lead had been unplugged when the set first came to me and then after all repairs etc done, had been refitted to the set.
My Test Cable--with The Bulb was made from an SC/P board cable from an older PZ70 set, and was quite firm on the plug pins.
The original to the repaired set was much looser in its fit to the pins of the board. Very careful examination of the board pins showed a VERY SLIGHT pitting in the form of a line across the supply pin--but no discolouration/black/burns. Fitting and removing the plug on the pins a few times, removed most of this...
So--Once its repaired (Again!) I'm gonna cut the bloody plugs off and solder the damned cables solid!
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