Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

[tom66]

Got another PZ80...actually two. This PZ8BA for £35 on eBay I'm working on now, and a 10 blink PZ85 (which is already fixed, common fault) for £50. Nice to score two at once...

This one is different to my previous PZ80 which had same symptom: that one had no 5VSTBY, due to AC DET fault on PSU. This one does have 5VSTBY so it points to A board.

Going to look into the A board now...

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Hmm, STB3.3V is dead (47mV), STB5V is present on A board...
15kohm to ground so not shorted. Generated on A board.
I am thinking IC2403 (C1AB00002877) is bad, as that appears to be STB3.3V source... hope I can source it. Looks easy enough to replace.

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Hmm, STB3.3V is dead (47mV), STB5V is present on A board...
15kohm to ground so not shorted. Generated on A board.
I am thinking IC2403 (C1AB00002877) is bad, as that appears to be STB3.3V source... hope I can source it. Looks easy enough to replace.

What do you think about injecting 3.3v there externally?

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Gonna try that tonight.
I've also got the PZ85 I can pull A board out of and see what that does, it's not 100% compatible but ought to get panel to show something...

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Gonna try that tonight.
I've also got the PZ85 I can pull A board out of and see what that does, it's not 100% compatible but ought to get panel to show something...

It'll be interesting to follow and learn

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Tried feeding in 3.3V, no joy, board just sucked up 700mA and no power light, so guessing that the ASIC does a few other things too and it's bad.

Will try swapping A boards over soon.

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Bingo, unplugged A board completely, click-click, primed screen followed by white. Panel looks good, as expected no burn in. Will try swapping A boards next.

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Swapped A boards over and it fired into life with a perfect picture.
So need to fix this A board, hmm...

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

If anyone knows of or has a good source of 68874Y03 please let me know (IC2403)
Can find one from Italy for £12 but that will take over a month given how Italian post works.

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

So resistance to gnd on the ASIC for the 3.3, did they match with the working board and the dead?

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Good board 14.3kohm, bad board 15kohm, no significant difference.

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

If anyone knows of or has a good source of 68874Y03 please let me know (IC2403)
Can find one from Italy for £12 but that will take over a month given how Italian post works.

could send an enquiry to CHS, who's the major panasonic repairer in the UK?

Send GTV Watford a message through EBay, although I think he's heavy handed with $. I've done that but contacted local panasonic parts distributor and local ended up cheaper.

is'nt one of our members in the UK a panasonic repairer?

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Good board 14.3kohm, bad board 15kohm, no significant difference.

So I wonder, how does a 15k load pull 0.7A on 3.3V? Or am I am looking at this too simplistically?

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

So I wonder, how does a 15k load pull 0.7A on 3.3V? Or am I am looking at this too simplistically?

Can be a parasitic diode, if it's hiding behind a diode drop for example, inside the IC. Damaged semiconductor structures can do anything. They can be completely non obvious when parasitic SCR structures or broken transistors get turned on. There's probably 50 or 100 transistors just involved in the regulator portion of that IC.

Will shoot off some messages to the other guys - can also buy the part from USA for $6 plus ??? shipping, so maybe I'll try that. C1AB00002877.

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Found a Polish supplier, but I think they only ship to Poland, no country selection.
EncompassParts various sites want minimum $200 order, ugh.

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Found a Polish supplier, but I think they only ship to Poland, no country selection.
EncompassParts various sites want minimum $200 order, ugh.

Yeah, I have the same issue. No O'S shipping or they want a huge$

I have uses freight forwarders once for an Ic , blew the cost right out. Ok if the purchase for a number of goods.

All we need really is for someone to volunteer to order it and then forward it

PM sent

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Managed to get another chip, from an incompatible board... (TH-42PZ800B) which I promptly swapped over.

STILL DEAD! 3.3V is dead. Checked soldering... all looks good (did it again to be sure)

Then I noticed burn damage around one of the HDMI ports. I figure this is power surge damage. I've found a pricey board on eBay (£45) but have ordered it... it's got an additional VGA port but I should be able to make it work.

I figure this TV has been a victim of a power surge through HDMI, maybe the Analog Devices HDMI part is damaged, and that has an active short - perhaps loading the 3.3V down too much. Even if I could get this set working, there's almost no chance the HDMI port(s) would work. Hence why I need a new board.

[Agent24]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Perhaps the burnt protection components are causing a short. At least remove them, clean the area and see what happens?

[tom66]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Not shown in the photo, but the HDMI IC also has a burn hole in it... and they are only termination capacitors/resistors not protection components unfortunately.

[tw2005]

Re: Panasonic TH-42PZ8BA completely dead (no standby LED), 5VSTBY present)

Managed to get another chip, from an incompatible board... (TH-42PZ800B) which I promptly swapped over.

STILL DEAD! 3.3V is dead. Checked soldering... all looks good (did it again to be sure)

Then I noticed burn damage around one of the HDMI ports. I figure this is power surge damage. I've found a pricey board on eBay (£45) but have ordered it... it's got an additional VGA port but I should be able to make it work.

I figure this TV has been a victim of a power surge through HDMI, maybe the Analog Devices HDMI part is damaged, and that has an active short - perhaps loading the 3.3V down too much. Even if I could get this set working, there's almost no chance the HDMI port(s) would work. Hence why I need a new board.

nasty, lightning comes to mind