CRT vertical deflection -- bad solder joints?
Sean Hamilton
Is it likely that bad solder joints would cause vertical foldover in a
mid-90s CRT television? I have a Hitachi TV which had vertical
foldover for a few months, which went away after it warmed up. Then
one day, no vertical deflection at all. I pulled the board out and a
lot of the solder work is terrible. However, the problem seems more
like a bad capacitor -- but they all seem fine, at least with visual
inspection. So I'm not sure where to go from here.
Thanks in advance,
William Sommerwerck
to clean them up, simply to reduce the chance of future problems.
tm
"Sean Hamilton" <seanha...@gmail.com> wrote in message
news:fa3b18fc-cf26-4f79...@l14g2000pre.googlegroups.com...
Look for a non-polar capacitor in the vertical deflection area somewhere
around 10 uF. Try replacing it.
tm
D Yuniskis
Bad cap.
Though, while you've got your head in there, you could reflow
any joints that look disgusting (taking care, of course, not to
*add* to your problems!)
William Sommerwerck
> any joints that look disgusting (taking care, of course, not to
You should really remove & replace the solder, not just reflow it.
Meat Plow
Electrolytic capacitors will often "warm up" and work well enough to
satisfy the circuit until they fail completely. If you can map out the
vertical signal and amp section(s) you might want to first hit some
suspect solder joints. After that is still no deflection you'll need to
scope out where your signal is lost.
--
Live Fast Die Young, Leave A Pretty Corpse
whit3rd
> Is it likely that bad solder joints would cause vertical foldover in a
> mid-90s CRT television?
Yes. The first place to look is the big fat pins that the deflection
yoke connector plugs into. Unplug the yoke connector
from the main board before reflowing the solder, it can
get stuck permanently if you don't.
Usually, the hint of bad solder joints is in sensitivity to
vibration (give it a whack, it works for a while). Overheated
switch transistors and bad coupling capacitors can also
kill vertical sweep, and if the screen only has half the
vertical sweep range, it could be a push-pull amplifier
is now only a push. Or only a pull.
b
A visual inspection is not enough here. resolder all the pins on the
IC, change the associated caps, they're cheap enough and often there
is no reliable way to test them.
Also check for an open circuit feed resistor in its b+ line (probably
from the line output transformer).
Using the tv with poor regulation of the supply to the frame chip
probably ended up damaging it, so you might have to change that too.
they're not usually dear though.
-B
John Robertson
Yup, my first suspect too. This cap is normally found attached to the
vertical deflection transistor electrically closest to B+. They are not
always non-polarized. On our Sanyo video game monitors they were regular
10ufd/250V. Find one that has a good ripple current rating if you want
the replacement to last...
John :-#)#
--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
Sean Hamilton
> Yup, my first suspect too. This cap is normally found attached to the
> vertical deflection transistor electrically closest to B+. They are not
> always non-polarized. On our Sanyo video game monitors they were regular
> 10ufd/250V. Find one that has a good ripple current rating if you want
> the replacement to last...
> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
It turns out I live a few blocks from to you. If I brought in just the
board, would you be able to take a look at it? You seem to be far
better equipped to deal with this -- I don't even have an
oscilloscope. I assume it would take less than an hour, since I
already did the boring part of getting it out of the cabinet. How much
would you charge for this? Reply by email if you wish.
Thanks,
Mike Tomlinson
s.com>, Sean Hamilton <seanha...@gmail.com> writes
>Is it likely that bad solder joints would cause vertical foldover in a
>mid-90s CRT television?
Yes, but it's more likely to be a bad cap.
> However, the problem seems more
>like a bad capacitor
Yes.
> -- but they all seem fine, at least with visual
>inspection.
Visual inspection is not enough. You need an ESR meter.
--
Mike Tomlinson
whit3rd
> In article <fa3b18fc-cf26-4f79...@l14g2000pre.googlegroup
> s.com>, Sean Hamilton <seanha...@gmail.com> writes
>
> >Is it likely that bad solder joints would cause vertical foldover in a
> >mid-90s CRT television?
>
> Yes, but it's more likely to be a bad cap.
> Visual inspection is not enough. You need an ESR meter.
Maybe not; the ESR issues crop up mainly in high-performance
low voltage power supplies (like computers); the vertical
sweep circuit doesn't need a low-ESR capacitor. It will
take (and work well with) just about any capacitor with
adequate voltage rating and capacity.
The capacitor is inexpensive; just replace it with a new one,
don't bother with testing the old unit.
Arfa Daily
"whit3rd" <whi...@gmail.com> wrote in message
news:157d392f-817a-4788...@glegroupsg2000goo.googlegroups.com...
I think you are missing the point of what he was saying regarding ESR. This
parameter is a valid test of the 'goodness' of any electrolytic capacitor,
regardless of its ESR pedigree. Even 'normal' electrolytics have a
relatively low ESR when they are properly functional. As they fail, that
figure will increase, and that is readily spotted with an ESR meter. As to
the OP's actual problem, whilst bad joints in vertical output stages in CRT
televisions were common, this more often lead to initially intermittent, and
finally permanent frame collapse, than geometry problems like foldover,
which the OP said was the problem he had. My money would be 100% on it being
a bad cap, or possibly the feed resistor to the output IC having gone high.
This was also a relatively common problem on many chassis, and could cause a
severe foldover, usually at the bottom of the screen where the deflection
drive current needed to be at its highest.
Arfa
Mike Tomlinson
egroups.com>, whit3rd <whi...@gmail.com> writes
>The capacitor is inexpensive; just replace it with a new one,
>don't bother with testing the old unit.
*whoosh*
And how is he supposed to locate the offending capacitor without some
form of test equipment?
--
Mike Tomlinson
Mike Tomlinson
<arfa....@ntlworld.com> writes
>I think you are missing the point of what he was saying regarding ESR.
I think so too :o)
>My money would be 100% on it being
>a bad cap
+1
--
Mike Tomlinson
Mark Zacharias
news:h9Lw4IA1...@jasper.org.uk...
Just look for the 100uF at 35v cap next to the output IC. :-)
Mark Z.
William Sommerwerck
the vicinity" while the bad-looking solder joints are being re-done?
This is a common problem in servicing. As an EE, I want to know exactly why
something isn't working correctly. But I learned a long time ago that it's
more important to simply get the damned thing fixed. If that means
shotgunning likely components, so be it.
Mike Tomlinson
<grizzle...@comcast.net> writes
>This is a common problem in servicing. As an EE, I want to know exactly why
>something isn't working correctly. But I learned a long time ago that it's
>more important to simply get the damned thing fixed. If that means
>shotgunning likely components, so be it.
If you're fixing stuff regularly, particularly many of the same item,
it's worth diagnosing the problem so that in future you can say, "oh,
that model, that fault, it's C35", and replace that - saving time and
the cost of replacing components unnecessarily.
--
Mike Tomlinson
whit3rd
> "whit3rd" <whi...@gmail.com> wrote in message
> news:157d392f-817a-4788...@glegroupsg2000goo.googlegroups.com...
> > On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
> >> In article <fa3b18fc-cf26-4f79...@l14g2000pre.googlegroup
> >>
> >> >Is it likely that bad solder joints would cause vertical foldover in a
> >> >mid-90s CRT television?
> >>
> >> Yes, but it's more likely to be a bad cap.
> >
> >> Visual inspection is not enough. You need an ESR meter.
> >
> > Maybe not; the ESR issues crop up mainly in high-performance
> > low voltage power supplies
> I think you are missing the point of what he was saying regarding ESR. This
> parameter is a valid test of the 'goodness' of any electrolytic capacitor,
A test, yes; but not a complete test. The ESR of a 10uF capacitor can be
good, but it won't do the work of a 100 uF capacitor. A combination
of ESR and capacitor-meter testing is better, and a test at the
frequency of interest for ripple reduction is better still.
I wouldn't bother with any of that parameter testing, though.
If you suspect the 10-year-old capacitor, replace it. You'd possibly have to
desolder to test it anyhow, spend the eighty-five cents to put in a new
one.
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:imsmrd$5nf$1...@dont-email.me...
Shotgunning is, IMHO, very bad practice, and often leads to the creation of
more problems than it fixes. I am actually quite surprised that you would
advocate doing this, William.
Arfa
Arfa Daily
"Mike Tomlinson" <mi...@jasper.org.uk> wrote in message
news:U6QNJSBZ...@jasper.org.uk...
Seconded ...
Arfa
William Sommerwerck
>> exactly why something isn't working correctly. But I learned a long
>> time ago that it's more important to simply get the damned thing
>> fixed. If that means shotgunning likely components, so be it.
> Shotgunning is, IMHO, very bad practice, and often leads to the
> creation of more problems than it fixes. I am actually quite surprised
> that you would advocate doing this, William.
I don't understand how shotgunning can /create/ problems, as long as the
replaced components are correct replacements. Unless you mean the customer
might get upset.
As an experienced service technician, you know that the cause of a given
problem is not always obvious, even after extensive troubleshooting. The
customer is paying for your time, often more than what the parts cost. Why
burn up the customer's money when replacing a half-dozen parts is likely to
fix the thing?
Mark Zacharias
news:Pyvkp.993$KZ7...@newsfe08.ams2...
I have seen sets (notably Toshiba and Mitsubishi) where shotgunning was
advisable in addition to replacing whichever single cap might have been
causing your issue.
Mark Z.
Meat Plow
We used to call some of the factory repair 'kits' for certain Panasonic
sets "shotgun packs" because of the amount of components included.
Some of those even included parts not on the board that were to be
added on the solder side.
Mike Tomlinson
>But I learned a long time ago that it's
>more important to simply get the damned thing fixed. If that means
>shotgunning likely components, so be it.
Would you be happy for a car mechanic to shotgun a fault on your car,
with you paying for his time and all the parts he is unnecessarily
fitting?
--
Mike Tomlinson
Meat Plow
Isn't that an unfair comparison?
William Sommerwerck
>> get the damned thing fixed. If that means shotgunning likely
>> components, so be it.
> Would you be happy for a car mechanic to shotgun a fault on
> your car, with you paying for his time and all the parts he is
> unnecessarily fitting?
Yes, if an initial /conscientious/ troubleshoot didn't reveal the problem.
I'd rather pay for parts than time.
Of course, you can't draw an exact parallel between cars and electronic
equipment. It's easier to "see" what is wrong with mechanical devices, but
car parts tend to be more-expensive than electronic parts.
Smitty Two
Mike Tomlinson <mi...@jasper.org.uk> wrote:
>
> Would you be happy for a car mechanic to shotgun a fault on your car,
> with you paying for his time and all the parts he is unnecessarily
> fitting?
It's commonly done. Had a girlfriend a few years back who took her car
in because it was overheating. They called with the estimate (of many
hundreds of dollars,) saying they had determined that it needed a new
radiator, new water pump, new thermostat, and new hoses.
I went down there and asked them how they had determined the radiator
fault, and they claimed to have pressure tested it. A 15 second look
under the hood confirmed my suspicion that they had not.
I took the car and replaced the thermostat - $12 and 1/2 hour - and it
served her for several more years.
The shop in question is consistently voted winner of the annual
"Reader's Poll" in our local rag.
Oddly, I don't think they operate that way solely to cheat the customer
financially. I think they're more driven by not wanting any return
complaints. That's why the "Readers" like them -- "they fixed it right
the first time!!"
I drove around town for the next 3 months with a giant sign in my back
window:
"Richard's Auto: As Crooked As the Day is Long."
I got a lot of stories from people who saw the sign, about their own bad
experiences there.
William Sommerwerck
>> car, with you paying for his time and all the parts he is unnecessarily
>> fitting?
> It's commonly done. Had a girlfriend a few years back who took her car
> in because it was overheating. They called with the estimate (of many
> hundreds of dollars), saying they had determined that it needed a new
> radiator, new water pump, new thermostat, and new hoses.
> I went down there and asked them how they had determined the radiator
> fault, and they claimed to have pressure-tested it. A 15-second look
> under the hood confirmed my suspicion that they had not.
> I took the car and replaced the thermostat -- $12 and 1/2 hour -- and it
> served her for several more years.
> The shop in question is consistently voted winner of the annual
> "Reader's Poll" in our local rag.
> Oddly, I don't think they operate that way solely to cheat the customer
> financially. I think they're more driven by not wanting any return
> complaints. That's why the "Readers" like them -- "they fixed it right
> the first time!!"
There's also the possibility that a comprehensive makes it possible to offer
a "lifetime" warranty on the repair.
> I drove around town for the next 3 months with a giant sign in my back
> window:
> "Richard's Auto: As Crooked As the Day is Long."
> I got a lot of stories from people who saw the sign, about their own bad
> experiences there.
It goes without saying that if a service shop claims that lots of things
need fixing, it's probably not telling the truth.
Thirty years ago I worked part-time -- at $6/hour -- for Chestnut Hill Audio
in Philadelphia. The owner said to me "You're not as fast as the other
people I use -- but nothing you repair comes back."
I had a holy horror of callbacks. It costs the business money, and it makes
the business and the service tech look bad.
By the way, I never shotgunned anything I repaired there, because nothing
seemed to need it.
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:imu10l$dit$1...@dont-email.me...
Every component that is replaced, increases the potential margin for error
by the person replacing it. I have had many items cross my bench over the
years, which have been 'elsewhere' first, and have seen wrong values fitted,
caps in backwards, diodes in backwards, damaged print and so on, amongst the
many components that have have obviously been shotgunned, as evidenced by
the flux all over their joints. I have also seen unsuitable substitutes
fitted, where technicians have had insufficient understanding of the
requirements of a circuit's design, and have just put in 'what came to hand'
in order to complete their shotgun.
Very occasionally, it is necessary to replace a block of components, when a
fault is particularly obscure, but I would never recommend it as an
acceptable procedure to anyone who wasn't hugely experienced in the field of
service work, and particularly in the case of a simple problem such as the
OP has with his TV's field scanning, and which would be easily diagnosed
with the use of appropriate test equipment.
Arfa
Arfa Daily
"Mark Zacharias" <mark_za...@sbcglobal.net> wrote in message
news:4d932454$0$31449$c3e8da3$c14f...@news.astraweb.com...
Occasionally, this is true, but only - for me at least - if the manufacturer
has recommended a block of components to be replaced, on the grounds that
some or all of the additional ones, may have been unacceptably stressed or
damaged, by the primary failure. In these cases, the manufacturer or his
spares agent usually supplies 'service kits' of all the necessary
components. Often the case with switch mode power supplies.
As in, for instance
Arfa
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:imvm1k$cqb$1...@dont-email.me...
I'm not at all sure you would say that if one of the incorrectly fitted
parts was the EMU, for example. This, and many of the expensive sensors on
engines nowadays, are usually 'bonded' parts, and once the box has been
opened, the supplier will not accept it back, which leaves you paying for
it, when it was not required. A while ago, I had just this problem with my
local garage, who replaced a cartload of parts and sensors on my engine, for
an idle problem that ultimately turned out to be due to a split in the PCV
hose. I argued with them long and hard about having to pay for parts that
had been shotgunned due to the fact that the guy doing the job had not
correctly diagnosed the problem. I eventually had to settle for a reduced
labour bill to offset the unnecessary parts cost, which they were determined
were staying on the engine, and that I was going to be paying for (at retail
price, just to make it worse)
Arfa
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:imvpdu$p1l$1...@dont-email.me...
Which is precisely what I'm saying. Yes, there are some items - notably
switch mode power supplies - where it is often prudent, or even recommended
by the manufacturer, to replace a whole raft of parts, but for most general
repairs, the cause of the problem should be correctly diagnosed, and the
(usually) one faulty component replaced.
Arfa
Arfa Daily
"whit3rd" <whi...@gmail.com> wrote in message
news:a40cc351-8a75-4797...@glegroupsg2000goo.googlegroups.com...
I hear what you're saying, and it does, on paper at least, have some
validity. However, my comments are based purely on many many years'
experience of doing service work on electronic equipment, from all walks of
life from consumer through industrial, and on a daily basis. I replace bad
electrolytic caps all the time. Several items every week will require bad
caps finding and replacing, and in just about every single case, the ESR
meter tells the story. In fact, it is probably the most useful test
instrument to live on my bench, and has paid for itself many times over.
Whilst I accept that electrolytics *do* fall in value, I find it actually
quite rare. Almost always, if a cap has fallen in value, its ESR will also
be out of the window. In my experience though, the reverse is often not
true. Having found a bad cap with my ESR meter, I do occasionally check the
value on my digital C meter, and for the most part, find it to be well
within tolerance.
As to having to remove caps to test them, again this is rare, and quite
impractical on complex switchers which may have many electrolytics, and more
than one that is faulty. I don't know if you are personally involved in
commercial service work, but in today's economic climate, and with the low
value of much equipment, the name of the game is quick and accurate
diagnosis of a problem, and minimising additional costs of time and
materials. I have never been an advocate of 'shotgunning' faults by
replacing components which may or may not be faulty. I have had many items
pass across my bench over the years which have come from other service
outfits who have replaced components 'willy-nilly' that they suspected to be
faulty, but without ever getting to the bottom of the original problem, and
having compounded that original fault in their efforts. I have had caps
fitted backwards, diodes and transistors fitted backwards, wrong value
resistors fitted, print damage and so on. So personally, I like to have a
bit more than a suspicion that a component is faulty, before replacing it.
In the case of electrolytics, my ESR meter, for the most part, does that for
me. In saying that, however, I think that I should also say that I fully
accept that the use of an ESR meter is as much black magic as science and,
although it is a useful instrument when used by its instruction manual, for
the professional user, there is also a considerable amount of interpretation
and 'feel' involved. In 'casual' hands, an ESR meter may be little better
than a multimeter for finding bad caps ...
One place where it can fool you is where an electrolytic has gone short
circuit - fairly rare these days, but does happen. In that case, the ESR
meter will of course, give a nice low reading that will, initially at least,
fool you into thinking that the cap is (probably) good.
Arfa
William Sommerwerck
> by the person replacing it. I have had many items cross my bench over the
> years, which have been 'elsewhere' first, and have seen wrong values
fitted,
> caps in backwards, diodes in backwards, damaged print and so on, amongst
the
> many components that have have obviously been shotgunned, as evidenced by
> the flux all over their joints. I have also seen unsuitable substitutes
> fitted, where technicians have had insufficient understanding of the
> requirements of a circuit's design, and have just put in 'what came to
hand'
> in order to complete their shotgun.
Yes, but you and I don't make such mistakes.
Mike Tomlinson
<mhyw...@yahoo.com> writes
>
>Isn't that an unfair comparison?
Tell me how. Not being argumentative, I'd be genuinely interested to
hear why you think it's unfair.
--
Mike Tomlinson
Mark Zacharias
If the parts are cheap with little or no additional labor, and done to
prevent a repeat failure in the near time frame, as is often the case with
TV's, then yes, I would be happy, and so are my customers.
Mark Z.