Power transistor question...

"Dave" <

** Verticle ???

It is not a faulty power transistor in the vertical output - or their would be no pix at all.

** MIL ?

Is there a fourth letter missing .....

** Sounds normal to me. ** Loss of vertical HOLD is far more likely to be a fault in the small signal circuitry OR the power supply.

Can you still adjust the vertical frequency to get the picture viewable - but rolling ?

The first thing to check is all the filter and coupling electros in the vertical and PSU for the vertical.

You need an ESR meter or lotsa luck.

.... Phil

Is the TV capable of receiving digital TV? If not, you'll need a converter and a way to power it.

is a digital battery powered 7" handheld TV with a whip antenna and the charger for $50 + shipping. This would be a better solution. Just charge the battery once in a while and it'll be ready in an emergency.

--
It's easy to think outside the box, when you have a cutting torch.

Phil is correct. The vertical output isn't likely to be the problem. Look specifically in the sync separator and vertical oscillator areas for your problem. The vertical oscillator isn't being locked to the vertical sync pulses. That's why the picture is rolling. Of course, the first thing to check is the power supply voltages and ripple in those circuit areas. Clean power is essential to proper operation of any circuit.

--
David
dgminala at mediacombb dot net

Whatever...

Yeah, hadn't thought of it that way. See comments further down.

Mother-In-Law. No fourth letter.

Yes, but the picture is only half the size of the screen at that point. Attempts to adjust the vertical hold so as to enlarge the picture result if more rolling. The 100K pot has to be maxed out to make it stop, and once it is no longer totally maxed it starts rolling again. Thinking of stuffing another 20K resistor in there to see if that changes anything...

Guess I'll need lotsa luck. What does an ESR meter actually measure, pray tell?

Thanks again. Have been running all day and am just now coming to the end of it all.

Dave

"Dave" "Phil Allison"

** It will tell you if an electro cap has or is about to die of old age.

Does this by measuring its internal resistance or ESR independent of actual cap value in microfarads.

ESR = Equivalent Series Resistance.

.... Phil

A good one

"Ken" "Phil Allison"

** Looks very nice.

Such ESR meters can also measure the ESR of cells, both rechargeable and non-rechargeable types -the very low test current means they can check Lithium button cells too.

The ESR of non-rechageables is good guide to remaining capacity - far better than voltage is.

The ESR of a NiCd or NiMH cell is a good guide to its heath and ability to deliver high currents.

Egs:

AA alkaline = 0.1 ohms new, rising to about 2 ohms at end of life.

AA carbon/zinc = 0.5 ohms new, rising to 5 ohms at end of life.

AA NiCd or NiMH = 0.03 ohms new, rising to 0.5 ohms at end of useful life.

9V volt alkaline = 0.8 ohms new, rising to 10 ohms at end of life.

Lithium button cell ( ie CR2032 ) = 10 to 15 ohms new, rising to 50 ohms at end of life.

.... Phil

Thank you Ken, and Phil. I had no idea. Definitely want one of those. Much appreciated.

So anyway, if my voltages look good and there's no serious ripple anywhere, I'm thinking more and more about the electro caps, but really don't fancy pulling each and every one out to test without having some sort of strategy as to which to test first. Any ideas on that? Larger ones first? What would you guys do? I truly do appreciate the help and ideas.

Dave

"Dave"

** OK - the " old school " way of doing this tedious task was to briefly parallel any suspect electo with a similar value and voltage cap while the set is operating.

And see WTF happens.

TV service was never a game for the faint hearted..............

.... Phil

Now believe I already have an ESR meter, though I didn't realize that was one of its functions. What I have is an Extech 380193 LCR meter, which tells me that a fairly new but run of the mill 1uF electrolytic cap out of my junkbox has 12.5 Ohms of resistance. If I were to try to use this to measure the caps in-circuit, how should I proceed? I am guessing that discharging the cap before touching my test leads to the solder pads would give me a reading, but I really hesitate to do this without some sort of suggestion that such is a safe proceedure for my meter. Am guessing that readings in the single digits indicate a defective device. Does this sound reasonable? No power to the circuit under test, of course, and likely will push in the power button a few minutes before beginning. Again, any advice is appreciated.

Thanks,

Dave

"Dave"

** Seen this ??

All you need to do is compare the ESR reading of a known good electro of about the same ratings and size with the one under test. If the one under test has say 5 times more ESR - it is useless or about to fail.

Often, with worn out electros, the ESR may be over 100 ohms.

.... Phil

No, I haven't seen that before. *Thank you.* Need to check and see if they have any others I could use. Am continually amazed by what I find available on youtube.

Is there anything special you know about testing a cap in-circuit with a meter like this? Am still a little worried about maybe damaging my LCR meter. It was a Christmas/Anniversary/Birthday gift from my loving wife some 8 or 10 years ago, and would like to keep it in good working order. Can't tell you how much I appreciate your help thus far with the subject at hand...

Thanks again.

Dave

"Dave"

** Just make sure the electros are discharged - short them if in any doubt.

.... Phil

"Dave"

** Just make sure the electros are discharged - short them if in any doubt

.... Phil

*** The meter being damaged is not a problem if things are discharged. The other issue is will this meter give accurate in-circuit readings? ESR meters use a very low AC voltage of typically 100 mV, a frequency of 100 KHz or so, and a very low source impedance to make the test. This minimizes the influence of other circuitry in parallel with the capacitor on the measurement. If your meter uses a higher voltage or places DC bias across the capacitor, in-circuit test results may not be accurate.

David

Kills 9V batteries. Otherwise, good price and good unit with many features that I'll never use.

That will work, if you happen to have a known good and identical capacitor handy. I have a fair collection of electroltyics but not every value and voltage.

The problem with the Extech 380193 Handheld LCR meter is that it will measure ESR at 120Hz and 1KHz. ESR is usually measured at about

100KHz. Dave Jones mentions this at about 12-13 minutes into his video. This is because electrolytic cazapitors exhibit a minimum ESR around 100Khz.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Not a bad little meter for the $$$$. Anyone who does work on consumer electronics ought to have one or something similar. Removes a lot of guess work.

--
Live Fast Die Young, Leave A Pretty Corpse

"Jeff Liebermann" "Phil Allison"

** Gotta pick you up on this one !!

That link shows ESR curves with frequency of a couple of * CERAMIC * capacitors of unusually high values.

ESR meters intended for in circuit testing of electros by service techs simply measure the cap's IMPEDANCE at around 100kHz. At this frequency - all but the lowest value electros have their minimum impedances and the values obtained are very close to ESR values at the same frequency. This allows one to compare electros for (high frequency) ESR and pick out faulty examples very easily.

OTOH, the Extech meter is designed to measure L and C values for a wide range of inductors and capacitors and uses to standard test frequency of

1kHz as used in countless other instruments. This means it is NOT intended to perform in-circuit testing of L and C value as other circuitry that may be in parallel may spoil the readings.

However, in the case of electros with values from say 4.7 uF and upwards and fitted to a TV set I would expect readings to be OK and the ESR values obtained to be useable. It would be a good idea to re-test any electros that are removed cos the ESR reading seemed high.

IMO - the 120 Hz frequency should only be used for out of circuit testing.

..... Phil

"Meat Plow"

** I disagree.

An LCR meter is more useful for design and production than in servicing.

Many low cost DMMs include capacitance ranges that can measure from a few pF up to 200 or 2000uF.

A dedicated ESR meter handles electros just fine while in circuit - and lets you test all kinds of cells too, which an LCR meter often cannot.

Any DMM can read the resistance of an inductor or transformer winding.

The only function left is to measure inductors for value.

.... Phil

Oops, y'er right. Sorry(tm).

Oddly, while the ESR of the ceramic caps are much lower than electrolytics, the curve shapes seem to be similar.

Googling, I find:

Note the dip in ESR and loss tangent at around 100KHz on various graphs.

Yep. Agreed on all points.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558