Bad tuner?

well, tapping on the neck board to get the picture back indicates to me you've got a tube going bad, or bad solder joints on the neck board. considering the amount of high voltage floating around there, i'd suggest you fix that first.

if your AV jacks have perfect signal, and you're piping RF directly into the thing..then, yes, it sounds like you have a defective tuner, you may try tapping the tuner itself and see what happens. my RCA XL100 console has a tuner issue like that. my GE 36" has a tuner that stopped functioning, it's basically locked between channels 2 and 3 judging from the noise i'm getting.

quite honestly, i don't see where analog RF tuners are a necessity. We've already started moving away from that with DVD players. I've in fact considered "building" basically a box with a medium resolution video monitor and then getting the hardware to convert baseband (composite)/S-video and interlaced progressive signals to native RGB.

A bad tube won't make snow, but I suppose there might be some strange arrangement where power for the tuner routes through the neck board. More likely the tapping is just jarring a loose connection inside the tuner, this should be easy to fix by just resoldering the bad one.

Very common problem is a bad PLL IC in the tuner SDA3202-2 is the number and it's an absolute bitch to replace.

In message , James Sweet writes

He was talking about tapping the neck board solving a blank raster, not the tuner problem. It certainly does sound like a bad tuner but I'd check all the voltages first, if it's missing one it could cause this problem, check the 'net for a datasheet and work from there.

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Clint Sharp

Thanks Ron, I'll see if I can find a datasheet for this to learn more about this IC. I'm guessing you mean it's a bitch to replace due to it's size? Any idae what the component costs?

Thanks for the response Clint. Your right, tapping solved the raster problem, not the tuner. I'll take your advice and see what I come up with. This is what I was wanting to know before trashing the set. A new tuner is $92.00. The set is 17 years old, but really has a good picture through the A/V inputs. To all I didn't reply to, Thanks for your help. Again I'm a beginner, and have learned alot from all of you visiting this group.

again, i'd say chck the solder joints, and if you check the volage, check it on both sides of the solder joint. many times you'll have voltage at the solder point, but due a fine crack in the solder, it loses continuity.

while probably not an issue, make sure when you remove a componet, you try not to remove the platated throuh holes.

The reason the SDA3202-2 is hard to change is the fact that its mounted on a small board in the tuner that has metal brackets on each side of it, and it solders all the way through the board, not just on the end of the legs, so the only way I know to change it is to have small snips, cut off all the legs, remove the body of the chip, then with a very small soldering iron try to heat one leg at a time as you pull each out until they are all removed, the carefully solder wick the excess solder off which is hard because it goes clear through the board, then poke any plugged holes clean with a small needle. All this is done with numerous surface mount resistors and transistors right where you are working, so careful going. After all this simply mount and solder the new chip in and set is fixed 100% of the time. I've done

30 or 40 of these over the years.

Thanks Ron. Iv'e been trying to butter up a tech in my area that owns a repair shop for some apprenticeship learning by loaning him my LC-101 since his is broke, buying winstips for both of us etc. Long story short, I told him the symtom of the set and he started to talk about a chip in the tuner. I asked if it was the PLL, he said yes. I said you suggested this as a probable fault, and was a mother to change. He told me exactly what you just typed above. I will take a little of everyones advice, check for voltages, solder connections, etc. Then will definitely jump on the PLL, what ever this does (I do know it stands for phase locked loop). This is why I like this group. Learn something new everyday. Thanks a ton to all. Will post a follow up soon on outcome.

OK, now I see what your talking about. This is gonna be a son of a b*%&h. Now, I had to remove the crystal to get my dikes in there. Should I replace the crystal since I'm in here, or are these pretty much dependable long term? Thanks. P.S. I checked with Mouser and the IC is $11.00. Does this sound high?

If the TV has good pciture through A/V inputs, why not get a set top external tuner (or VCR) and connect to AV ins. Beats replacing the tuner (and paying $92 on a 17yr TV).

It's the position...you have to cut pins on the IC, etc., to get it out, and too much heat can easily ruin some solder pads...if I remember correctly.

Tom

Hmmm...double-sided solder also?

Tom

On 16 Jun 2005 12:22:42 -0700, snipped-for-privacy@cox.net put finger to keyboard and composed:

I don't have any experience with your particular set, but here are some general tips.

Meter the tuner's pins. It appears that your tuner is getting power (B), otherwise you wouldn't see snow, just a white or black screen. Check that the band switching pins (BU, BH, BL) respond to band changes (UHF, VHF high, VHF low). Also check that the tuning voltage (VT) increases and decreases smoothly as the channels are scanned.

See the bottom RH corner of this page for a typical pinout:

- Franc Zabkar

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Please remove one 's' from my address when replying by email.

But he said tapping fixes it, I've never seen a vibration sensitive IC before.

In message , James Sweet writes

No, he didn't say that, he's stated twice now that the tapping only cured the no pic fault. Once he'd got the tube working then he discovered the tuner didn't work. BTW, I have seen a vibration sensitive IC, must have been a bond wire or something but it was an EPROM which 'looped' back to 0 intermittently when you were trying to read above

0x03fff. Tapping the chip would cause the problem to appear more frequently and could be demonstrated in a little test jig we threw together because it was such an unusual fault.

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Clint Sharp

Clint, again you are right. I tapped the board on the picture tube neck to get raster. I have checked tuner voltages and I seem to have all of them. I ordered the PLL ($11.00). Will try this per Ron's advice since nothing else found wrong. I did get the old one out without damage to the surface mount components I hope. I need to add that I didn't exactly have a totally black screen. I could barely see snow in the picture, but pretty much black screen. I have since re-soldered everything on the neck board, so we'll see if this works. Thank you to all that have replied. Nice to communicate with professionals. Will post a follow up when component gets here and installed.

Oops, I missed that. Yeah it could certainly be a bad tube, but try resoldering the neck board first, it's easy. If it still has that symptom then just scrap it.