After successfully replacing a MoBo in a laptop computer with this crippled up body,I've been presented another challenge.<G>.
The patient, victim, or recyling fodder is a 2002 vintage Panasonic CT-27D32F Chassis:QP338.Initially,the issue it had was random start up and shut downs due to my younger son's rough handling while using the head phone jack.I suspect fractured traces on the front of the PCB.That has not yet been addressed.
Something new has been added recently. Upon start up the Horizontal Frequency is off, low.After thirty seconds or so of operation it would sync up.
That's been tolerable for about a month. This AM upon start up, a shriek came from the set, much lower than Horizontal Frequency,{ Yes, at 57 my EARS are still that good.},and could not be shut down without unplugging it.A quick look at the CRT neck revealed no heater present ,and I suspect this set uses a scan derived or similar power supply.( A quick scan on the Web has shown this to be an issue with these sets.)
I obtained a partial FSM online by subscription, and it looks like enough to get one into real trouble.[Why Panasonic took the fractured approach to FSMs is beyond me.]
So my question to this august group is, what have you seen cause these symptoms, and should repair be attempted? The set performed well enough that one can see just how bad ATSC images can be. <VBG>

Thanks for you time, and I hope this long read has at least provided some amusement.

As a professional tv tech, it seems the problems are now suited for an experienced servicer to deal with.
It's obviously out of the hands of tinkerers- partly due to the continued use since the problems started.

"Upon start up the Horizontal Frequency is off, low.After thirty seconds or so of operation it would sync up.
That's been tolerable for about a month." - you waited a month too long, I'm afraid.

It's been two generations since there was a TV/Radio tech in the clan.(The last one was my Grand Dad,one of the if not the first TV dealer/techs in the Pittsburgh area,before WDTV was even built out.)I will see what other contributions or observations are made before throwing in the towel.

And RT, if you do have vehicle problems it will be my endeavour to assist you in any way possible.That was a thought planted in my head by my Grand Dad. FWIW

Thanks a bunch.
But alas, when I hear a strange engine noise, or get a flat tire, I immediately have it tended to before the problem causes more damage.

Not all issues are as apparent,nor easily diagnosed.That happens in all vocations and walks of life, sooner or later.Sometimes passing the baton yields better fruit than throwing down the gauntlet.

That's why since my disability, I do consulting and troubleshooting for my comrades that can still wrench.What I have learned benefits no one if it stays between my ears.

The original problem was quite likely a bad electrolytic cap. The most common failure for an electrolytic cap is increasing ESR (Equivalent Series Resistance) with age. The ESR tends to go down as the capacitor heats up, so the set will initially have a problem when cold but work when warmed up. The problem now could be a harder failure of the bad cap or you could now have a bad transistor, SCR or integrated circuit.. When the horizontal runs at the wrong frequency, that is quite hard on the other parts.

When electrolytic caps start to fail the top of the case will often bulge out, but not always. You could open up the set and look for any bulging caps. If you find any, it will not cost much to try replacing them. To test the caps that look alright you would need either an ESR meter or a capacitor tester that will measure the ESR. An ESR meter can be used with the capacitors still in circuit.

If you can't find a bad cap then you would need the schematic for the set and an understanding of how the circuits in the set work.

I've been through the counterfeit capacitor saga on two computer MoBos and the ERC on our Tappan stove.{ That stove control is only a cool $400.00 and would likely have the same failure prone fake Nichicons. } So far those items have remained functional ,post repair.

This is precisely the type of feedback that I was hoping to have surface. Thanks !

I suspect that what you now have is a shorted horizontal output transistor. This TV probably uses a switching power supply and when the HOT shorts, it places a very heavy load on the power supply; thus, causing the loud squealing sound. Also, don't leave it plugged in for very long in this condition as it is highly possible that the short will burn up the power supply. Check the HOT with the diode test function of a DMM. If it is shorted, it will need to be replaced with a transistor of the same type number. I have used NTE/ECG generics; but, I'd rather use a genuine part with the correct part number. Also, stay away from cheap semiconductors from discount mail order outfits. Many of these are highly inferior Chinese knock-off's and they will often either fail upon power up or fail shortly thereafter (don't ask how I know this).

Before you replace the HOT, you'll need to find out what's causing the horizontal to go off frequency. The top suspects would be bad electrolytic caps in the power supply, the horizontal oscillator circuit, and/or horizontal drive circuit. Another cause could be bad solder connections. This is especially true on power resistors of 1W or more, heat sink mounted semiconductors, and transformers. You also need to check the B+ voltage against the schematic value. If this voltage is off or not well regulated, that could cause problems.

As far as newer TV's go, Panasonic seems to be a good brand and I would at least make an effort to fix it. Someone just gave me a 32" Panasonic from 2000 with the common problem of top foldover and little white horizontal lines at the top of the screen. I pulled the plug as soon as I saw this because it's a common problem with all brands and the cap that causes the problem will blow out the vertical output IC at any given moment.

After this 'tinkerer' had his head handed to him,{By a professional, no less.},the "I have nothing to lose mode" was engaged.I managed to slide the set out of the entertainment center, onto my thighs and then onto the floor. ( Those of you that know me are aware of the career ending spinal cord injury that matured five years ago, so this was no mean feat.) Removing the rear of the cabinet revealed a sight that would have dazzled my Grand Dad beyond belief.
An entire 27 inch color TV chassis that hardly fills two hands.I remember him and other local techs grousing over how tightly packed the Japanese tube sets were getting and the transistorized sets promised to be much WORSE.
Back to the mission.After marvelling at what a great electrostatic precipitator a nearly ten year old CRT set can be, I set to cleaning things up to perform the necropsy.[Otherwise, there would be an autopsy performed on ME after my XYL cornered me about the mess in the living room.] <G>
The first thing that caught my eye were three large,(compared to everything else) electrolytic capacitors.Two are 150 uF @ 200V, one is 220uF @ 200V.Two really have their plastic swim suits shrunken in response to heat, the third one, not so much.
The two that looked like they have been really warm responded to an ohm meter test as one who fixed vehicles for 35 years would expect.Low resistance that would then rise. But behind door number three, on a 130V line, this gem shows dead open.
For those of you that have dug out your Sams or your Panasonic Sectionalized FSM, the dead capacitor is C 809,{150 uF} the two that appear to be physically ill are C 805 {150 uF} and C 806{220 uF}.

Any thoughts on the possibilities of these observations being noteworthy ? More details if you can stand them. <VBG>

RJ

Well, if number 3 starts high and stays there, that is a possible cause of your initial problem. And it is quite likely that all 3 should be replaced. Still unknown is if you now also have a blown transistor.

If you replace the capacitors you should get 105 degree C parts, and ones rated for high ripple current would be good too. But you could stick in any capacitor with the right value and voltage rating for a test. You need the good parts for long life.

Agreed.
Just like in motor vehicles, the repair is only as good as the quality of replacement parts and the care with which they are installed.

Change those caps and check the HOT.

I'm a BRAND new member here.....and I mean new, like I registered about an hour ago.

I'm starting to see that ANY CRT tv set is called "old".....and my newly aqcuired collection of "micro" TV sets....Most of them are just old, but I did "continue" my dad's collection, and have acquired a couple Sony transistor sets I would call valid antiques.

I used to work on TV sets in high school (early '80s), and am now 46...and finding myself now JUST getting back into "restoring" some eighties to naughties sets. Dad left me like twenty small TV sets of just varying degrees of "cool", but they are mostly 2"-5" sets and are not really high drama to get going again (usually just dirty).

Yesterday I was walking a swap meet.....and found a Sony 301W. Looks like NOW I officially have a restoration. I could NOT pass it up...has the whole antenna, ALL it's knobs... bright chrome on both sides and DOES have it's little sun shield. I musta walked PAST that thing like four times before I was afraid someone was gonna snatch it up.

For the thirty bucks he wanted.....I would have been perfectly happy if it was just a shelf queen, but....it DOES come up, with difficulty, so I went online TODAY to sort of OFFICIALLY get into this hobby

Now, for a $64,000.00 Question.Is it even possible to check a HOT with tools I have lying around the house when it contains an integral damper diode ?

You can check it with the diode test function of a DMM or the Rx1 setting on an analog VOM.

For best results, it would be best to check the HOT out of circuit; but, 9 times out of 10, you can get a good idea of it's condition while still in the circuit. Place one meter probe on the center terminal of the transistor (collector), place the other probe on the base terminal and note the meter reading. Now, reverse the meter probes. You should only get a reading one way. If you get a reading both ways, the HOT is shorted. Now, move the probe that was just on the base terminal to the emitter terminal and repeat the above test. If you test between the base and emitter while the HOT is still in circuit, you will read a short because you are reading across the secondary winding of the horizontal driver transformer. Some HOT's not only have a built in damper diode; but, also a resistor. At any rate, if you have a reading both ways between C and E or C and B, the transistor is shorted.

One thing that seems odd at first is that a transistor can be shorted emitter to collector but have the base to collector and base to emitter junctions check out as good. The emitter to collector short is a very common failure when a transistor overheats enough to partially melt inside.

What manner and type of image attachments are permissible here ?

After more briefing...........Let's see what happens THIS time. Based on what I see here, the HOT is going to have to be removed for testing.Does anyone concur?

You may be able to test for a collector to emitter short in circuit, but to test it completely it will have to be removed from the circuit. If the base and emitter leads are soldered to a circuit board, you may be able to remove the solder well enough to have the leads not connected to the foils. If you can do that then you do not need to remove the transistor from the heatsink.

I got ambitious today and extracted the HOT. C to B weighed in at 38 ohms. In BOTH directions.C to E showed 0.6 ohms in both directions. B to E ,38 ohms in both directions. The damper diode is across C and E, the resistor is across B and E and has a nominal value of 45 ohms according to the Toshiba data sheet.

I suspect the HOT is toast.

RJ