TNPA5349 Buffer replacement

[tw2005]

Re: TNPA5349 Buffer replacement

Sorry TW that is just my cockney sarcasm the bit about the truck battery, I used to work as signal tech on the London underground ,on the ticket vending side (auto fare collecting) and each station had a room full of coding and decoding equipment, That magnetically encrypted a code to the back of the ticket, that was read by the auto gates as you passed though, this was so complex that when things went wrong find the faults were a big problem, and I was the only tech and on call for the Victoria line (was new then)and Bakerloo line. When a tech on another line ask one day how I checked for shorts I told him with a truck battery (as a joke) and he burnt out about four miles of wiring and nearly burnt down the strand station Happy days Flocko

hard to pick the sarcasm in text. no joy with the photo i guess?

[flocko]

Re: TNPA5349 Buffer replacement

Sorry TW that is just my cockney sarcasm the bit about the truck battery, I used to work as signal tech on the London underground ,on the ticket vending side (auto fare collecting) and each station had a room full of coding and decoding equipment, That magnetically encrypted a code to the back of the ticket, that was read by the auto gates as you passed though, this was so complex that when things went wrong find the faults were a big problem, and I was the only tech and on call for the Victoria line (was new then)and Bakerloo line. When a tech on another line ask one day how I checked for shorts I told him with a truck battery (as a joke) and he burnt out about four miles of wiring and nearly burnt down the strand station Happy days Flocko

[tw2005]

Re: TNPA5349 Buffer replacement

Hi TW Yes I cannot say I was not warned, but I would not think these two missing tracks would make the board a right off, as you can see were they go to on the ribbon socket ,its more the short that is the time killer trying to find that, I could try the old trick of putting some volts though it and watch for the smoke (24v Truck battery)? the photos are stills from the microscope but just wont download on to here Flocko

The short has me puzzled, that's for sure. No photo is a real tease. so what format is the still and what's it's dimensions ?

A truck battery, hope not direct to it, it has enough current to vapourise anything, i think you'd want to limit the current somehow. I've never experimented applying voltage to a short to find heat

[flocko]

Re: TNPA5349 Buffer replacement

Hi TW Yes I cannot say I was not warned, but I would not think these two missing tracks would make the board a right off, as you can see were they go to on the ribbon socket ,its more the short that is the time killer trying to find that, I could try the old trick of putting some volts though it and watch for the smoke (24v Truck battery)? the photos are stills from the microscope but just wont download on to here Flocko

[tw2005]

Re: TNPA5349 Buffer replacement

it was the silicon that done for me, you can only get off what is over the pins but it must be very fluid when its put on, as it seeps right under the chip, used hot air and lifted it in one corner and then flipped it on its back, but you could see the tracks had been pulled up by the silicon as went over it was the last part to let go that pulled the tracks, I keep trying to load photos but don't seem able to. Newtothis the boards are out there you just have to know were to look? Flocko

yeah, and that was the point i was trying to make about getting all the silicone off. When i had a go I cut the pins against the chip, then got the ic off , no issue( took a lot of force)but I still had some sealant on the pins and it was that that grabbed the tracks as i was desoldering the legs and tore the tracks.

have you checked the size of the photo, not larger than 2000 x 2000, that will stop it uploading

[flocko]

Re: TNPA5349 Buffer replacement

it was the silicon that done for me, you can only get off what is over the pins but it must be very fluid when its put on, as it seeps right under the chip, used hot air and lifted it in one corner and then flipped it on its back, but you could see the tracks had been pulled up by the silicon as went over it was the last part to let go that pulled the tracks, I keep trying to load photos but don't seem able to. Newtothis the boards are out there you just have to know were to look? Flocko

[newtothis]

Re: TNPA5349 Buffer replacement

If i remember right Acetone will eat sealant

[tw2005]

Re: TNPA5349 Buffer replacement

Well the buffer removal did not go to well lost two tracks, tried to put up photos but for some reason it will not let me. anyway the short remains on SN2, I can only put so much time into this board,I would have liked to fix it but will now put it to one side and come back to it later, but will also keep a eye open for a replacement board, thanks for all the help, I will keep you updated if I find the short Flocko

blessed are those who can do this. how did you go with that sealant removal?

[newtothis]

Re: TNPA5349 Buffer replacement

Well the buffer removal did not go to well lost two tracks, tried to put up photos but for some reason it will not let me. anyway the short remains on SN2, I can only put so much time into this board,I would have liked to fix it but will now put it to one side and come back to it later, but will also keep a eye open for a replacement board, thanks for all the help, I will keep you updated if I find the short Flocko

Good luck finding one that is affordable or worth it, They are as rare as rocking horse crap believe me as I am hunting one myself.

Mine had had a previous repair attempt before I purchased this set and it did not go well for the board, Torn up tracks and pads, multiple shorts blah blah blah All my IC's are fine so may well try and get it repaired if i cannot source an affordable replacement.

Also sorry I have not been on for the last week as I have a IR rework machine here

[flocko]

Re: TNPA5349 Buffer replacement

Well the buffer removal did not go to well lost two tracks, tried to put up photos but for some reason it will not let me. anyway the short remains on SN2, I can only put so much time into this board,I would have liked to fix it but will now put it to one side and come back to it later, but will also keep a eye open for a replacement board, thanks for all the help, I will keep you updated if I find the short Flocko

[flocko]

Re: TNPA5349 Buffer replacement

Thanks guys ,I will be back on to this late this afternoon, have to go out this morning. But anything you think could help me track down this short, or any tips for removing the buffer cleanly on these new Panasonic boards please post here Flocko

[tw2005]

Re: TNPA5349 Buffer replacement

Didn't you have one from Brazil...? will have to dig it out...

I have 50", GT30 went looking for 42", maybe I just don't see it

[tom66]

Re: TNPA5349 Buffer replacement

Didn't you have one from Brazil...? will have to dig it out...

[tw2005]

Re: TNPA5349 Buffer replacement

tw, do you have a schematic of this board?

as per NEELIX, by the time you enlarge it, too hard to read. I'm not understanding how a shorted buffer chip can short sn2. I experimented with shorting vfo to vfg on a X20 Sn and did not cause sn2 to short

[tw2005]

Re: TNPA5349 Buffer replacement

I have now started to go round checking on the pads were the legs have been lifted on the diodes + IGBTs to see if any show shorted there was a small Fet Q600 that I had missed but there is no short on that. I will also pull the 2 cap from across SN2 socket as well do you think that I am right about the test across the diodes by the buffers as these show short?

the smd diodes next to buffers will sow short and is normal. you'd have to lft them if you want to be sure

[tom66]

Re: TNPA5349 Buffer replacement

I repaired one a while ago (TX-P42U30B) and I quite liked it when working...

[Neelix]

Re: TNPA5349 Buffer replacement

Saw service manual for same SN board, but circuit diagram is poor quality and can't make out a thing

[flocko]

Re: TNPA5349 Buffer replacement

Tom just had a look and Alastair repaired one a little time ago. but he has not been on here for a while,

[tom66]

Re: TNPA5349 Buffer replacement

tw, do you have a schematic of this board?

[flocko]

Re: TNPA5349 Buffer replacement

After checking the pads no shorts found, But now think the anodes on D461/462 (RFN20) are the floating ground for the buffers as if you diode test from here to tab connectors you get IC 4803 showing short in diode mode and 200ohm ? only way to see if this the short at SN2 is to take buffer from board will get on to that tomorrow afternoon.