Panasonic TX-P42ST30B the 'ol 6 Blinks

[foxyUK]

Got rid of 7 blinks by changing the usual 6 IGBTs and the FETs & Fuse on the P board that always seem to go on the 42's.
Changed IC502 which was dead, but not Q531 which diode-checks OK.
First look at the 6-blinks, found Q441 suspect (not short, but lowish resistance) so tried an FGD4536. Mid voltage 190v... no good. Salvaged a DG302 from a spare SS board and still 6 blinks, but Mid is now 85 volts (a bit low) until the point where shutdown is initiated, and then it instantly shoots up to around 200v....is that normal? (Given that at the moment I don't know why it is shutting down).
The green LED on the SN illuminates briefly, but not the one on the SS, and no fan start.
15v, 5v, Vscan, Vad, all normal.
I have a 100w lamp in the Vsus, but it's hitting 215v OK.
Is there a way to confirm it's the SN board without disconnecting C20 from the C2 board as described in the troubleshooting flowchart (which looks to be inaccessible)?

Thanks

[tom66]

Re: Panasonic TX-P42ST30B the 'ol 6 Blinks

Do you have access to a scope? Preferably a digital one?

[foxyUK]

Re: Panasonic TX-P42ST30B the 'ol 6 Blinks

Unfortunately I don't have access to a 'scope, and I only tinker with these series 30 plasmas because I learned how to fix the SC on one for my own use and they seem to crop up regularly in my local area, so have done four 50" models. The 42" seems to be a bit more of a nuisance!
I realise that my dmm with Min-Max is not fast enough to catch all that is going on with MID properly. I'll change the other DG302 just in case, and maybe Q531 that measures OK with diode check but may be different with higher voltages?

[foxyUK]

Re: Panasonic TX-P42ST30B the 'ol 6 Blinks

Okay.... got there.
It was the other DG302, Q551. Strange devices these! In circuit the resistances were not deeply suspect, and diode check gave fluctuating results, which was odd. Tested properly out of circuit, the device was fully conducting with low voltage and hardly conducting at all at 5-6v, pretty much the inverse of normal operation.

[budwich]

Re: Panasonic TX-P42ST30B the 'ol 6 Blinks

good to see / hear you found the issue. gives me some hope to go back on my board and recheck those dg302s as the power up / mid voltage was similar.... maybe.