awwwwww yeah

[weirdlookinguy]

Re: awwwwww yeah

Parts ordered today. Will let you guys know how it goes.

[mockingbird]

Re: awwwwww yeah

I'm glad you got it upstairs. I told you all you needed was a little elbow grease. Don't forget to discharge the tube properly (flat headed screwdriver, wire attached to it and then clipped to the long spring on the left or right side of the aquadag. Insert screwdriver to the point underneath the suction cup, hear a pop, repeat every 15 minutes till it pops no more).

[Wizard]

Re: awwwwww yeah

Mockingbird's advice about discharging CRT with loud snaps! NO *I advise NOT TO DO THIS!* This is HV probe is for this but not necessary because work is only working on circuit board and does not require unhooking from CRT.

Newer CRT TVs electronics is more sensitive to violet discharging of CRT and my advice is leave it alone. Work with circuit board propped up with HV wire still attached to the CRT. Ditto to ground wire still attached. Use resistor of about 10K ohms
to slow discharge the main power supply capacitor if voltage check found this cap still charged up.

I do this all the time with TVs like this. Very rarely I have to bring out the HV voltage probe to gently discharge and detach the HV clip and cup.

Cheers, Wizard

[mockingbird]

Re: awwwwww yeah

I did this on several TVs and never heard any popping so I am just quoting from allegory.
You're smarter than I on this topic, but when I have had to work on a CRT board before, I've had to take the thing out completely or else I couldn't see what I was doing and I had to desolder the ground wire.

[PlainBill]

Re: awwwwww yeah

Most modern CRT designs use a voltage divider to derive the focus voltage from the 2nd anode voltage. This will discharge the the CRT over the course of a few minutes. Yes, it is a good idea to make sure the CRT is discharged before you disconnect the HV lead. Back in the days when there were no semiconductors in the TV, shorting the 2nd anode directly to chassis ground was acceptable. It isn't any more.

PlainBill

[weirdlookinguy]

Re: awwwwww yeah

Thanks for the suggestions guys, but I will just simply avoid the anode wire and prop up the circuit board like Wizard suggested. I've worked on many CRT TV's (mostly late 80's - early 90's stuff, nothing modern like this WEGA) and I never once discharged them. I just left the anode wire alone.

I will discharge the filter caps though, because I will be replacing them.

One quick question - I clicked on the wrong Panasonic cap when I ordered from Digi-Key last night (for the 1200uf 250v filter caps) and they are neither Low ESR nor 105c. Since they are only filter caps, this should be fine... right? I plan on keeping this TV around for a good 5 or 6 years.

[Wizard]

Re: awwwwww yeah

I forgot to add:

And another reason not to do this violent shorting of CRT to dag ground (taut wires across the bell of CRT) is not advised is that internal dag is thin. Where the CRT connector button is, sometimes this blows the dag coating connection open causing resistance to rise. That could ruin the CRT.

Cheers, Wizard

[weirdlookinguy]

Re: awwwwww yeah

This TV could not have impressed me more. I pulled it apart and this is why it sounds so good:


Built-in subwoofer. It's a very interesting contraption and I think it's brilliant how they made use of the extra space that is usually wasted on CRT TV's. Not only that, but the L and R speakers are 2-ways. Each side has a separate tweeter and a midrange. Sony did NOT have to do that, one full-range speaker on each side would have done the trick.

The tube is made in USA.

There are separate circuit boards for everything. Even the audio section has its own PCB.

The main board (Power Supply, CRT drive) has all japcaps and Delta transformers.

The decoding board for the dual tuners and HD processing is big, with good heatsinking and a full metal EMI cage around it.

This thing is fit for a king. None of the space and cost saving compromises you see in today's flat panels.

[weirdlookinguy]

Re: awwwwww yeah

Let's get down to brass tacks, gentlemen.

The victim:


Tools of the trade:


Are you are a fan of Where's Waldo? Me either, fuck Waldo. I don't give a rat's ass where he is. For this reason, I have highlighted the components going under the blade:


The aftermath (new socketed IC's, new filter caps and 2 of 3 fusible resistors replaced):


I went ahead and reflowed the solder on the flyback and every transformer on the board. The result?


GREAT SUCCESS .

[ratdude747]

Re: awwwwww yeah

question: i see you used ratshack braid and a tip held in by a screw. my experience with such tools was the braid had no flux and was therefore useless and the irons with tips like that tended to have poor heat transfer and the tips warped really fast, only to find that there are no replacement tips..

did those tools work well? just wondering... since it is a PSU single layer board, i imagine those tools would work for that type board, but i still wonder.

btw, nice work!

[weirdlookinguy]

Re: awwwwww yeah

The ratshack braid worked OK. It wasn't the best but it did the job. Flux would have helped a lot, I didn't know that braid was supposed to have flux in it. I've had that braid forever and next time I buy some I will get fluxed braid at Fry's.

The iron is surprisingly decent. Heats up great and the tips last a long time. When they go, ratshack sells new ones for $2. I do have to tighten the screw from time to time.

The tools worked great for this board, but as you noted, it is a single layer PSU board and those boards are pretty forgiving. If I were to start soldering more delicate stuff, I would probably look at buying a better set of tools. That xytronic you always talk about looks great for the money.

[Wizard]

Re: awwwwww yeah

Why the sockets? This is big no no in TV where extreme thermal cycles occurs.

And good job on your fix but sockets has to go.

Cheers, Wizard

[weirdlookinguy]

Re: awwwwww yeah

MCZ3001DB seems to blow every 3-4 years in these TV's from what I've read online, I wanted to make it easier for future repairs. The chips are in the sockets very snug and the board is laying flat, not sideways, so gravity is on our side. Do you think I should go back and remove the sockets? I am tempted to leave them as-is.

[PlainBill]

Re: awwwwww yeah

MCZ3001DB seems to blow every 3-4 years in these TV's from what I've read online, I wanted to make it easier for future repairs. The chips are in the sockets very snug and the board is laying flat, not sideways, so gravity is on our side. Do you think I should go back and remove the sockets? I am tempted to leave them as-is.

Gravity has nothing to do with it; thermal cycling does. 30 years ago I had a Commodore PET; all the memory chips were socketed. It seemed like every month or two I would have to open it up and reseat the chips. That was easy - the top opened on hinges. I doubt this is as easy.

If there was clearance under the socket I would suggest trying to fashion a clip to hold the ICs in place. If they run hot, I'd suggest using a thermal epoxy to glue a heat sink on top of them.

PlainBill

[mockingbird]

Re: awwwwww yeah

That is a beautiful TV set, though I don't see the need for profanity.

[weirdlookinguy]

Re: awwwwww yeah

My apologies. The F-bomb was meant to be for comedic effect.

I guess I will pull her apart one of these days and solder the chips in properly. Here I was thinking that the sockets were going to save me work in the future....

[smason]

Re: awwwwww yeah

My apologies. The F-bomb was meant to be for comedic effect.

Well it worked, I LOLed when I read "F___ Waldo"

[Wizard]

Re: awwwwww yeah

Now I know what this chassis is.

The HV supply is NOT a old fly. This is truly a SMPS HV, much tighter HV regulation in the process means picture doesn't expand/shrink. I had scope on HV circuitry/drivers and drive is square pulses via 2 transistors driving by that IC in PWM method, exactly like a SMPS but this is for HV. The H-scan stuff is from via another transformer via huge heatsink (that what it is for).

Very nice TV indeed. The reason tv was here at our shop few years ago was blown HV transformer.

Oh, I saw you are using *CORRECT* sony part fusible resistors. Very good and very methodical.

I had a rear projection 3 LCD Sony, in SMPS board, one all in one DC to DC IC was leaky and sourcing one is out of question as it was given to us. Cost of IC is about 25-30. I can't believe the cost.
I chould had whipped out a whole DC-DC circuit from a plamsa SMPS and adjust resistors because of datasheet is available for 5 pin IC to get 6.5V from 17V supply. But I was not so sure because owner damaged it on purpose in many places, so can't know for sure if it work and I do not like 3 LCD Sony sets in general.

Cheers, Wizard

[ratdude747]

Re: awwwwww yeah

The ratshack braid worked OK. It wasn't the best but it did the job. Flux would have helped a lot, I didn't know that braid was supposed to have flux in it. I've had that braid forever and next time I buy some I will get fluxed braid at Fry's.

The iron is surprisingly decent. Heats up great and the tips last a long time. When they go, ratshack sells new ones for $2. I do have to tighten the screw from time to time.

The tools worked great for this board, but as you noted, it is a single layer PSU board and those boards are pretty forgiving. If I were to start soldering more delicate stuff, I would probably look at buying a better set of tools. That xytronic you always talk about looks great for the money.

the xytronic has limits too as i have found... it cannot do heavy ground planes like on macs or FIC boards. the 30w doesn't cut it for that. i wonder of they make a higher temp version of it?

[mathog]

Re: awwwwww yeah

The victim:

It will indeed be the victim come the next big quake. In round numbers, if that box weighs 160 pounds and there is .5g lateral acceleration the resulting 80 pounds of lateral force are for sure going to slide it right off the smooth tops of those supports. Assuming the supports have not fallen over first. Probably the only way you can secure that much mass would be to strap it firmly into a sturdy entertainment center, and bolt that in turn to the studs in the wall.

It would be a real shame to have put the effort into fixing up this nice set and then lose it due to a lack of earthquake restraints.