How do Regulators effect monitor picture? What purpose do they serve?

[OpFlash]

Hi there I have a WG 25" K7000.  I was wondering about certain parts as I recently did a cap kit and noticed that there are other parts available that are not included in your "basic" cap kit.  My picture is not 100 percent perfect but thats another post.  My question is how the regulators work on these monitors what their purpose is and if they are starting to go or are bad how that may effect picture quality?  for instance IC4 and IC3 on the WG K7000 what do they do?

[qrz]

the purpose of a regulator is just that . maintain a specific output voltage level within reasonable load levels and input voltage (regulation)
not sure how technical you wish this response 

in the k7000 Vreg should stay around 123v ( str3123 =123v, str3130 = 130v etc.. )
raw B+ needs to stay above 130v for regulator to function properly  (linear regulator)
IC4 is the Vreg IC , R301 is a "pass resistor" . which, takes some of the workload off IC4
the ic is self regulated ( internal bias circuitry ) . generally , this type of circuit eithers works or not ....
note: C18, C25, and C57 will affect Hosc stability amoungst other symptoms


IC3 is the Vertical Output IC .  this IC takes the vert drive pulse from IC2 and amplifies it (pw ramp) to drive the vert deflection yoke
vertical stages are a closed loop . meaning,  the output affects the input and visa versa.

[OpFlash]

Technical is cool.  I learned quite a bit here and helped understand some of the how and why.  Ok so I understand that the Vreg's are a type of part that either works or not.  So if one went bad then is it safe to assume that you would have a "dead" monitor or no picture?  Guess Im wondering because i just did a cap kit and picture was much improved but not perfect.  Im trying to find out if what im experiencing could be related to some other  parts not included with the cap kit.  I would prefer not to change parts that are working if i dont have to.  The situation that Im experiencing is what looks like 3 whiteish thin lines on the left side of the screen that are vertical going from bottom to top of screen.  You cant see these bars while game is playing but they are noticeable when the backround is black.  Not sure what the culprit could be. 

[MonMotha]

Is this monitor mounted horizontally (typical TV orientation) or vertically (ala Pac-Man)?

As for your technical explanation of the regulator's operation:

The voltage regulator is basically a linear (class A) amplifier with the input set to a fixed voltage and an output stage capable of handling a fair bit of current.  As the input voltage changes and the load current changes, the regulator develops a voltage across its internal (or sometimes external) pass elements (usually a bipolar transistor or sometimes a MOSFET) needed to hold the output at the fixed, set voltage.  An internal (or sometimes external) feedback loop makes it do this.

Since the feedback loop is so simple, failures are generally related to the thing being "completely broken" i.e. shorted or open.  A shorted regulator will simply pass the input voltage directly to its output, so the output will be too high and will have all the input nasties present.  An open regulator won't pass any power at all, and you'll have an apparently dead monitor.

Failures are usually due to heat, inordinately high current draw e.g. shorted component and a fuse didn't act quick enough, or unusually high input voltage.

Poor power quality can be due to a broken regulator or bad smoothing cap on the AC rectifier output.  In the case of a regulator that supplies B+ (the main voltage on the board from which other stuff is derived), like the STR3130 on a WG k7000 series, bad power can cause all sorts of problems.  In the case of a bad regulator or smoothing cap feeding B+, this tends to cause a horizontal blackish bar that scrolls up or down the screen or similar "wavy" effects since the power will be varying at 50/60Hz (depending on whether you're in Europe or the Americas), but other things can happen, too.

Most cap kits do not include the big smoothing cap that I just mentioned as it's, well, big, and it's also expensive and tends to not fail as frequently as other caps. It's also more tolerant of being slightly out of spec.  You might try replacing it if you suspect power quality problems.

A picture of these white bars you're talking about might help pin down the cause.

[boardjunkie]

IC regulators normally fail shorted, so that shoves the raw filtered DC straight thru it. The HT holddown circuit (x-ray protect) catches this (if its working properly) and it goes straight into protect mode. IE, you'll hear the degauss coil go "brrmp" and the crackle of HV static, then nothing. No tube neck filament, no pix. Measuring the voltage at both sides of the 25w resistor in the reg circuit and finding roughly the same thing on both sides confirms a shorted V reg.

The same rules apply for discrete reg circuits with to-3 pass transistors (WG4600,4900, GO7, etc), although they rarely fail.

[OpFlash]

looks like the bars that were showing up were due to a board issue as when trying a different board the bars were no longer noticeable