Panasonic TH-42PZ77U 7 blinks

[capkid]

Re: Panasonic TH-42PZ77U 7 blinks

yeah i may have been rude jumping in, but seeing how many FETs you were dealing with, I had this vision of you starting randomly on a bank lifting each when the bank was ok.

Down to 6 and if lucky q644 may be it. never touched these older sets.

enjoy, looks like a cheap fix coming up.

Not rude at all. I learned something myself. I didn't logically think to look for a short in a bank - duh, makes sense.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

out of curiosity start with Q644 since leg to leg was different

After lifting the right leg of Q644, the measurement is exactly the same as it was with both legs in circuit.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

After lifting the right leg of Q644, the measurement is exactly the same as it was with both legs in circuit.

All you want to do is check RL to tab as that is what was shorted. if it is with the leg up then recheck the bank and see if the RL short has gone or not.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

All you want to do is check RL to tab as that is what was shorted. if it is with the leg up then recheck the bank and see if the RL short has gone or not.

I don't know that I actually had a short. If you remember right, that one just read a little lower than the others. RL to tab (back of the transistor) is identical to what it was.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

I don't know that I actually had a short. If you remember right, that one just read a little lower than the others. RL to tab (back of the transistor) is identical to what it was.

RL to TAB is shorted that's why we're doing this. Just start at the first transistor and continue until you find one shorted on the RL and the bank no longer shows shorted. I just suggested that one since you said leg-leg was different.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

RL to TAB is shorted that's why we're doing this. Just start at the first transistor and continue until you find one shorted on the RL and the bank no longer shows shorted. I just suggested that one since you said leg-leg was different.

When I said the measurement was exactly the same, I meant on Q644. I had not checked the others. I'm a novice here but, I'm learning. I just checked the others starting at Q641 and with the leg of Q644 lifted, the measurement goes to .463 I held my leads on it with one hand and, used my other hand to push the leg of Q644 back down and Q641 went to .045 I guess this means Q644 is the cause of the problem? That one is shorted and shorts the whole bank til you take it out of circuit? Do I have this right?

You see me being a newbie to this, I didn't realize that the original .045 measurement was a short. I have a lot to learn.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

When I said the measurement was exactly the same, I meant on Q644. I had not checked the others. I'm a novice here but, I'm learning. I just checked the others starting at Q641 and with the leg of Q644 lifted, the measurement goes to .463 I held my leads on it with one hand and, used my other hand to push the leg of Q644 back down and Q641 went to .045 I guess this means Q644 is the cause of the problem? That one is shorted and shorts the whole bank til you take it out of circuit? Do I have this right?

You see me being a newbie to this, I didn't realize that the original .045 measurement was a short. I have a lot to learn.

oh ok, well then that proved to be a good guess because you remember you said leg - leg this was the only one different which I was hoping may have been a hint.

yeah so if it no longer reads 045 in bank with 644 lifted then that's it. you'd probably get away with firing the TV up with just 1 missing for a quick test or wait and replace it. lift both legs remove completely first though.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

oh ok, well then that proved to be a good guess because you remember you said leg - leg this was the only one different which I was hoping may have been a hint.

yeah so if it no longer reads 045 in bank with 644 lifted then that's it. you'd probably get away with firing the TV up with just 1 missing for a quick test or wait and replace it. lift both legs remove completely first though.

Lift both legs before doing the brief fire up test? It was a hint it's just I expected a bigger difference.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Lift both legs before doing the brief fire up test?

yeah , although may be read what others have tried but pretty sure a few have done that but don't run it longer than needed to verify that's all it needs as having one missing increases the load on the remaining FETs.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

yeah , although may be read what others have tried but pretty sure a few have done that but don't run it longer than needed to verify that's all it needs as having one missing increases the load on the remaining FETs.

I did see others doing that. They did say to only run it briefly. I'm gonna give that a go. Again thanks for all of your help.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

I gave her a go and with both legs of Q644 lifted, the tv powered up and the menu came up on screen. Looks like that's all I need to do is replace that. Sweet.

Now, am I going to need to use hot air to get the job done without damaging anything? In the other thread, a guy or two damaged their boards removing the FET

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

I gave her a go and with both legs of Q644 lifted, the tv powered up and the menu came up on screen. Looks like that's all I need to do is replace that. Sweet.

Now, am I going to need to use hot air to get the job done without damaging anything? In the other thread, a guy or two damaged their boards removing the FET

So what do you have? This is where you may need input from someone first hand. I think the damage would be not getting enough heat into it quickly. I'm tempted to suggest 80w iron with chisel tip flow fresh solder on the tab, heat until it starts bubbling on the sides and lifts off.

Dewick excess solder , flux pen then lightly tin the back of the new transistor tab. Place and heat, feed solder on the sides which should draw in. Heat so it goes right through . let cool then tack the legs to their pads.

Bound to be video on hand soldering smd fets

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

So what do you have? This is where you may need input from someone first hand. I think the damage would be not getting enough heat into it quickly. I'm tempted to suggest 80w iron with chisel tip flow fresh solder on the tab, heat until it starts bubbling on the sides and lifts off.

Dewick excess solder , flux pen then lightly tin the back of the new transistor tab. Place and heat, feed solder on the sides which should draw in. Heat so it goes right through . let cool then tack the legs to their pads.

Bound to be video on hand soldering smd fets

Right now I have an iron and a solder gun. I think the solder gun is 100w. Not positive. On Wednesday I expect delivery of a Weller soldering station. It has a temp range of 350 to 850°F (177 to 454°C). I see some hot air stations pretty reasonable that might be a worthwhile investment. I have solder wick and some canned flux.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Right now I have an iron and a solder gun. I think the solder gun is 100w. Not positive. On Wednesday I expect delivery of a Weller soldering station. It has a temp range of 350 to 850°F (177 to 454°C). I see some hot air stations pretty reasonable that might be a worthwhile investment. I have solder wick and some canned flux.

Never used a solder gun , honestly give it a go.if the solder has melted the transistor will need no force to move it.force and high heat lifts/tears the copper tracks . if it does not happen don't use force. Using a kids tablet . slow as for typing

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Never used a solder gun , honestly give it a go.if the solder has melted the transistor will need no force to move it.force and high heat lifts/tears the copper tracks . if it does not happen don't use force. Using a kids tablet . slow as for typing

Right. I don't want this to happen. https://www.badcaps.net/forum/showpo...8&postcount=67

I see you posted in that thread so you know what I mean. I have to wait for a new part anyway. I will watch some videos on it in the mean time.

Amazon has them. A place in the UK as well. http://sparedparts.com/search/a39630...6e60ccdddf6ca0

Again thank you very much for your help tw. You saved me alot of work.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

It happened anyway. #@!@%^@$%!@#^

[Neelix]

Re: Panasonic TH-42PZ77U 7 blinks

Did you use a hot air gun or soldering iron to heat up the tab?

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Did you use a hot air gun or soldering iron to heat up the tab?

I used a soldering iron. I'm thinking maybe I should just get a hot air unit. I don't think I need an expensive one. I'm not sure it would have made a difference since I've never tried it.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Well I tried to flow solder into that pad and it won't stick to the area where the copper pad was torn out.

I may have to just try it with what's left.

[bikerbuddy]

Re: Panasonic TH-42PZ77U 7 blinks

Rockguy it will help if u can use some chip quick to remove any smd chip without destroying the pad , it has a lower melting point and stay liquid long enough to remove the chip .I use it to remove large chips . works very well