Benq plasma salvagable or write off?

[andy]

...

[restorer-john]

BGA is not a problem for us, after all, most of our gear is vintage and the most you will find that is hard/impossible to fix is the 'printed' resistors that kenwood used in the 1970's or the sanken darlington packs that are unobtania, along with some wierd FETs, strange pallet output transistors and particularly oddball value large power supply caps. BGA is the provence of modern gear and it has no place in real hifi. As an example, when Sony ES went from all through hole to a mix of surface and through hole- the quality was gone. You can't put surface mount componentry in a power amp driver stage and not expect the things to blow up like fireworks. I know a certain 5 channel 25kg gold power amp from Sony that appears on eBay all the time where the driver transistors are tiny crumb sized surface mounts- what a joke. All this BS about shorter signal paths etc etc for a preamp, poweramp and reliability is complete rubbish. We all know through hole has the runs on the board in high current hifi applications. My policy is to not have any real hifi with surface mount in it. My CD players cross the line a little due to the odd surface mount IC, but basically after 1990/1 they all turned to crap in terms of construction. You can't have a dvd player without surface mount somewhere, but that's life i guess, no one uses one for serious hifi anyway.
The following rules will help you sort out real hifi from junk:
The output transistors are discrete and the more the better.
The power supply caps have a recognized brand on them and the larger value the better. (no flying pigeon brand or sun-moon brand etc etc)
The power amp stage has no ICs in the signal path.
The amp is heavy and solid.
It has a speaker A+B switch where they can run in parallel.
It has two phono inputs or a MM/MC input.
An integrated amp without a phono input is modern JUNK.
A tuner should weigh more than a bottle of milk.
The more heads and motors in a cassette deck, the better it is.
And my personal favourite which I apply to CD players. If you can't lift the machine up by the the CD drawer- it IS a piece of junk. (that means as a minimum, lift the machine off the shelf by the end of the drawer up to at least 45 degrees). The old machines can do it easily. A CDP101 can be held by the drawer. Early philips/marantzs can, as can most of the sony ES line, some denons and pioneers and others. I dare you to try it with some of these 'audiophile' machines that are held together with plastic clips- haha.
Anyway, enough ranting...
john

[ChrisW6ATV]

Bryan-

Look it up on Wikipedia. I wasn't familiar with it either, but after I read their article, I realized I have seen some boards with parts like that, particularly computer components.

Edit: Oops, I didn't see there was a third page and Andy already mentioned it.

[fujifrontier]

Originally Posted by compucat

You should probably replace it with a tube type color console.

God, I love that... it sounds so genuine.

I want to see pix of the innards!

[dr.ido]

Pictures will be posted when I get back there to work on it. I didn't bring it home with me (trying to man handle it around by myself is probably a guarantee that I would crack the panel).

[dr.ido]

The view after removing the 30 or so screws holding it together. It was manufactured in 2002. Judging by stripped screws posts and the texta marks on almost every board it has been repaired several times in it's 5 year life.

The small board at the top of the picture is carries the standby power supply and the audio amplifier.

The panel itself is made by Chungwhua. Most of the other components are known brands (Rubycon capacitors, etc). That kind of surprised me at first considering the kinds of off brand and left over parts I'm used to seeing in a lot of recent cheap electronics, but I guess that can't get away with the kind of shorts cuts I see in cheap CRT TVs/DVD players/etc here.




The signal board which provides VGA and DVI inputs and the daughter card which adds composite and component video inputs. The only BGA IC in the unit is on this card. There is a space and connector for another card, probably a TV tuner.



The X scanning board. It's mainly through hole components and loads of surface mount diodes. Some of the diodes have already been replaced in a previous repair.



The Y scanning board. More of the same. No visible repairs on this board.



The driver (?) board. A stack of FPGAs, buffers and some RAM. I'm guessing that in a brand name display they'd probably use some custom ICs here. One of the surface mount capacitors had already been replaced with a through hole part.



The power largely obscured by it's heat sink. This is all through hole bar one tiny module. I found 2 bad capacitors (1500uF/200V) here that appear to be filtering the 175VDC rail that drives the panel. I don't know if this is the cause of the red snow yet, I don't have any suitable replacements on hand. I have seen bad filter capacitors that measured okay cause snow in CRT sets before.

All in all it looks like plasmas are more repairable than I thought, though this may not apply to other brands/models. I'm going to replace the bad capacitors to see if the picture improves, but considering the damaged panel I won't be spending any more time/money on it otherwise. If the panel was okay I'd look into it further. If I knew exactly what I was looking at I could handle working on the power supply and scan boards. Someone with greater skill and a finer soldering iron than I have could work on the driver and signal boards (with the exception of the lone BGA IC).

[kcollins4]

Maybe someday I'll understand half of what you just said.
Great pics!

[ChrisW6ATV]

Nice pictures and description, dr. ido. I hope you have success with the capacitors, if only as a learning experience.