Power transistor question...

[Dave]

Have a very small (5" screen) black and white TV that has lost its verticle
hold. MIL would like it repaired if possible, and kept in storage in case
of another hurricane knocking out power and services like the last one did.
Upon opening it up I see a power transistor (2SB834) with signs of
overheating. My meter tells me that the E/B and B/C pn junctions are
switching at .574 and .572 volts, respectively. Am I missing the mark, or
does this sound a little low to others as well, as if the pn junctions have
been damaged? Its a few more minutes until my candy store opens, and
several hours before I'll be able to get by there, but to me, this
transistor souinds like a good candidate for replacement. Would appreciate
hearing what others think, if anyone cares to comment. Otherwise I'll bide
my time until I can prove the part one way or another. Just hope I don't
have to order the damn thing and wait a week.

Thanks for any comments...

Dave

 

[Phil Allison]

"Dave"
<

Have a very small (5" screen) black and white TV that has lost its
verticle hold.

** Verticle ???

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

MIL would like it repaired if possible,

** MIL ?

Is there a fourth letter missing .....

and kept in storage in case of another hurricane knocking out power and
services like the last one did. Upon opening it up I see a power
transistor (2SB834) with signs of overheating. My meter tells me that the
E/B and B/C pn junctions are switching at .574 and .572 volts,
respectively. Am I missing the mark, or does this sound a little low to
others as well, as if the pn junctions have been damaged?

** Sounds normal to me.

Its a few more minutes until my candy store opens, and several hours
before I'll be able to get by there, but to me, this transistor souinds
like a good candidate for replacement. Would appreciate hearing what
others think, if anyone cares to comment. Otherwise I'll bide my time
until I can prove the part one way or another. Just hope I don't have to
order the damn thing and wait a week.

** 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

 

[Michael A. Terrell]

Dave wrote:

Have a very small (5" screen) black and white TV that has lost its verticle
hold. MIL would like it repaired if possible, and kept in storage in case
of another hurricane knocking out power and services like the last one did.
Upon opening it up I see a power transistor (2SB834) with signs of
overheating. My meter tells me that the E/B and B/C pn junctions are
switching at .574 and .572 volts, respectively. Am I missing the mark, or
does this sound a little low to others as well, as if the pn junctions have
been damaged? Its a few more minutes until my candy store opens, and
several hours before I'll be able to get by there, but to me, this
transistor souinds like a good candidate for replacement. Would appreciate
hearing what others think, if anyone cares to comment. Otherwise I'll bide
my time until I can prove the part one way or another. Just hope I don't
have to order the damn thing and wait a week.

Thanks for any comments...

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

<http://www.geeks.com/details.asp?invtid=HLT71&cat=TVS&cpc=APM> 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.

 

[Dave M]

Phil Allison wrote:

"Dave"

Have a very small (5" screen) black and white TV that has lost its
verticle hold.

** Verticle ???

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

MIL would like it repaired if possible,

** MIL ?

Is there a fourth letter missing .....


and kept in storage in case of another hurricane knocking out power
and services like the last one did. Upon opening it up I see a power
transistor (2SB834) with signs of overheating. My meter tells me
that the E/B and B/C pn junctions are switching at .574 and .572
volts, respectively. Am I missing the mark, or does this sound a
little low to others as well, as if the pn junctions have been
damaged?

** Sounds normal to me.

Its a few more minutes until my candy store opens, and several hours
before I'll be able to get by there, but to me, this transistor
souinds like a good candidate for replacement. Would appreciate
hearing what others think, if anyone cares to comment. Otherwise
I'll bide my time until I can prove the part one way or another. Just
hope I don't have to order the damn thing and wait a week.

** 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

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

 

[Dave]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94ceigFhduU1@mid.individual.net...

"Dave"

Have a very small (5" screen) black and white TV that has lost its
verticle hold.

** Verticle ???

Whatever...

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

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

MIL would like it repaired if possible,

** MIL ?

Is there a fourth letter missing .....

Mother-In-Law. No fourth letter.

and kept in storage in case of another hurricane knocking out power and
services like the last one did. Upon opening it up I see a power
transistor (2SB834) with signs of overheating. My meter tells me that
the E/B and B/C pn junctions are switching at .574 and .572 volts,
respectively. Am I missing the mark, or does this sound a little low to
others as well, as if the pn junctions have been damaged?

** Sounds normal to me.

Its a few more minutes until my candy store opens, and several hours
before I'll be able to get by there, but to me, this transistor souinds
like a good candidate for replacement. Would appreciate hearing what
others think, if anyone cares to comment. Otherwise I'll bide my time
until I can prove the part one way or another. Just hope I don't have to
order the damn thing and wait a week.

** 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 ?

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...

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.

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

.... Phil

 

[Phil Allison]

"Dave"
"Phil Allison"

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.

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

** 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.

http://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors

..... Phil

 

[Ken]

On Sun, 29 May 2011 14:05:03 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Dave"
"Phil Allison"

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.

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

** 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.

http://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors

.... Phil

A good one
http://www.peakelec.co.uk/acatalog/jz_esr70.html

 

[Phil Allison]

"Ken"
"Phil Allison"

"Dave"
"Phil Allison"

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.

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

** 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.

http://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors


A good one
http://www.peakelec.co.uk/acatalog/jz_esr70.html

** 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

 

[Dave]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94e6r1Frd6U1@mid.individual.net...

"Ken"
"Phil Allison"
"Dave"
"Phil Allison"

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.

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

** 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.

http://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors


A good one
http://www.peakelec.co.uk/acatalog/jz_esr70.html


** 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

 

[Phil Allison]

"Dave"

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.

** 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

 

[Dave]

"Dave" <db5151@hotmail.com> wrote in message
news:N72dnaJJw6PhsH_QnZ2dnUVZ_hKdnZ2d@posted.internetamerica...

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94e6r1Frd6U1@mid.individual.net...

"Ken"
"Phil Allison"
"Dave"
"Phil Allison"

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.

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

** 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.

http://en.wikipedia.org/wiki/Equivalent_series_resistance#Capacitors


A good one
http://www.peakelec.co.uk/acatalog/jz_esr70.html


** 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

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

 

[Phil Allison]

"Dave"

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.

** Seen this ??

http://www.youtube.com/watch?v=zEA5MfllPdg

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

 

[Dave]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:94g5a0FfaiU1@mid.individual.net...

"Dave"

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.

** Seen this ??

http://www.youtube.com/watch?v=zEA5MfllPdg

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

 

[Phil Allison]

"Dave"

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.

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



..... Phil

 

[David]

"Phil Allison" wrote in message
news:94h8neF4dgU1@mid.individual.net...


"Dave"

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.

** 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

 

[Jeff Liebermann]

On Mon, 30 May 2011 10:05:12 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

** Seen this ??
http://www.youtube.com/watch?v=zEA5MfllPdg

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

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.

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.
<http://www.amccaps.com/leaded-capacitors/switch-mode-ceramic-capacitors/esr-vs-frequency.html>

--
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

 

[Meat Plow]

On Mon, 30 May 2011 10:05:12 +1000, Phil Allison wrote:

"Dave"

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.

** Seen this ??

http://www.youtube.com/watch?v=zEA5MfllPdg

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

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

 

[Phil Allison]

"Jeff Liebermann"
"Phil Allison"

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.
http://www.amccaps.com/leaded-capacitors/switch-mode-ceramic-capacitors/esr-vs-frequency.html

** 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

 

[Phil Allison]

"Meat Plow"

http://www.youtube.com/watch?v=zEA5MfllPdg

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.

** 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

 

[Jeff Liebermann]

On Tue, 31 May 2011 11:16:04 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

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.
http://www.amccaps.com/leaded-capacitors/switch-mode-ceramic-capacitors/esr-vs-frequency.html

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

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:
<http://www.low-esr.com/esrfreqperfcurves.asp>
Note the dip in ESR and loss tangent at around 100KHz on various
graphs.

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.

Yep. Agreed on all points.

..... Phil

--
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