Re: Dead Panasonic TH-85PF12E due to fault in AC DET circuit

It turns out the opposite is actually the case. The cap at the drains, which I guessed at around 4.7nF (and as used in the simulation traces), charges through the 22k and the other 22k from the 9V rail to the PNP base; it discharges through both these resistors [I]and[/I] the 220k at the drain. This gives time constants of 0.2ms for charge, and 1.2ms for discharge. The latter is easily seen by the upward curve of the blue trace over a handful of milliseconds. The smaller time constant is what gives rise to the short pulses...

My first proper post, mostly of a 'for information' nature, in that it might be of use/interest to others rather than being a call for help, as the problem encountered in our unit has been largely resolved. (A huge thank you to [b]tom66[/b] for [URL="https://www.badcaps.net/forum/showthread.php?t=28456"]this thread[/URL], which got me going in the right direction!)

The unit was sold (for a song) as unworking, having received a suspected large voltage spike during a thunderstorm when it stopped working. On applying power there was no response whatsoever - no relay clicking,...

Re: New Members - please post your introductions here

Hi everyone,
Came across this forum whilst Googling ideas on how to troubleshoot a completely dead Panasonic 85" plasma TV (a TH-85PF12E). The spur I needed was
[URL="https://www.badcaps.net/forum/showthread.php?t=28456"]this incredibly useful thread[/URL] by [B]tom66[/B]. Having reverse-engineered the equivalent 'AC DET' circuit in the '85, despite not being able to properly id a few components, we were able to scope the circuit and establish only half of it was working. A bit more head-scratching...