CRT vertical deflection -- bad solder joints?

S

Sean Hamilton

Guest
Hello,

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,
 
If the solder joints look bad -- they probably are. It would be a good idea
to clean them up, simply to reduce the chance of future problems.
 
"Sean Hamilton" <seanhamilton@gmail.com> wrote in message
news:fa3b18fc-cf26-4f79-8899-e45f302cb1e6@l14g2000pre.googlegroups.com...
Hello,

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,
Click to expand...
Look for a non-polar capacitor in the vertical deflection area somewhere
around 10 uF. Try replacing it.



tm
 
On 3/27/2011 11:26 AM, Sean Hamilton wrote:
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.
Click to expand...
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!)
 
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!).
Click to expand...
You should really remove & replace the solder, not just reflow it.
 
On Sun, 27 Mar 2011 11:26:56 -0700, Sean Hamilton wrote:

Hello,

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,
Click to expand...
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
 
tm wrote:
"Sean Hamilton" <seanhamilton@gmail.com> wrote in message
news:fa3b18fc-cf26-4f79-8899-e45f302cb1e6@l14g2000pre.googlegroups.com...
Hello,

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,

Look for a non-polar capacitor in the vertical deflection area somewhere
around 10 uF. Try replacing it.



tm
Click to expand...
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."
 
On Sunday, March 27, 2011 11:26:56 AM UTC-7, Sean Hamilton wrote:

Is it likely that bad solder joints would cause vertical foldover in a
mid-90s CRT television?
Click to expand...
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.
 
On Mar 27, 8:26 pm, Sean Hamilton <seanhamil...@gmail.com> wrote:
Hello,

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,
Click to expand...
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
 
On Mar 27, 3:00 pm, John Robertson <s...@flippers.com> wrote:
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
Click to expand...
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,
 
In article <fa3b18fc-cf26-4f79-8899-e45f302cb1e6@l14g2000pre.googlegroup
s.com>, Sean Hamilton <seanhamilton@gmail.com> writes

Is it likely that bad solder joints would cause vertical foldover in a
mid-90s CRT television?
Click to expand...
Yes, but it's more likely to be a bad cap.

However, the problem seems more
like a bad capacitor
Click to expand...
Yes.

-- but they all seem fine, at least with visual
inspection.
Click to expand...
Visual inspection is not enough. You need an ESR meter.

--
Mike Tomlinson
 
On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
In article <fa3b18fc-cf26-4f79-8899-e45f302cb1e6@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.
Click to expand...
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.
 
"whit3rd" <whit3rd@gmail.com> wrote in message
news:157d392f-817a-4788-b72b-5198c68bb1af@glegroupsg2000goo.googlegroups.com...
On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
In article <fa3b18fc-cf26-4f79-8899-e45f302cb1e6@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.
Click to expand...
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
 
In article <157d392f-817a-4788-b72b-5198c68bb1af@glegroupsg2000goo.googl
egroups.com>, whit3rd <whit3rd@gmail.com> writes

The capacitor is inexpensive; just replace it with a new one,
don't bother with testing the old unit.
Click to expand...
*whoosh*

And how is he supposed to locate the offending capacitor without some
form of test equipment?

--
Mike Tomlinson
 
In article <z2akp.203037$Bg2.147257@newsfe03.ams2>, Arfa Daily
<arfa.daily@ntlworld.com> writes

I think you are missing the point of what he was saying regarding ESR.
Click to expand...
I think so too :eek:)

My money would be 100% on it being
a bad cap
Click to expand...
+1

--
Mike Tomlinson
 
"Mike Tomlinson" <mike@jasper.org.uk> wrote in message
news:h9Lw4IA1zZkNFwZu@jasper.org.uk...
In article <157d392f-817a-4788-b72b-5198c68bb1af@glegroupsg2000goo.googl
egroups.com>, whit3rd <whit3rd@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
Click to expand...

Just look for the 100uF at 35v cap next to the output IC. :)

Mark Z.
 
Hello? Instead of fussing over it, why not replace all the electrolytics "in
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.
 
In article <imsmrd$5nf$1@dont-email.me>, William Sommerwerck
<grizzledgeezer@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.
Click to expand...
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
 
On Monday, March 28, 2011 5:51:41 PM UTC-7, Arfa Daily wrote:
"whit3rd" <whi...@gmail.com> wrote in message
news:157d392f-817a-4788-b72b-5198c68bb1af@glegroupsg2000goo.googlegroups.com...
On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
In article <fa3b18fc-cf26-4f79-8899-e45f302cb1e6@l14g2000pre.googlegroup
s.com>, Sean Hamilton <sean...@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

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,
Click to expand...
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.
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:imsmrd$5nf$1@dont-email.me...
Hello? Instead of fussing over it, why not replace all the electrolytics
"in
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.
Click to expand...
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
 
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